5 Speed Gear ratio advice?

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Let me say this, if I had the stash, it would be the 2.87 low with 3.91s minimum. If you check my sig, you'll see the ratios I am currently running, which is the best I've been able to come up with after five different factory combos. And I like it!
3.09-1.92-1.39-1.06-.78GVOD It has Splits of .62-.73-.78-.74od That 500 has a slightly wider 2-3 split and a slightly better od. It will be awesome! And it has potential for future growth with an SBM.
 
AJ/FormS said:
Let me say this, if I had the stash, it would be the 2.87 low with 3.91s minimum. If you check my sig, you'll see the ratios I am currently running, which is the best I've been able to come up with after five different factory combos. And I like it!
3.09-1.92-1.39-1.06-.78GVOD It has Splits of .62-.73-.78-.74od That 500 has a slightly wider 2-3 split and a slightly better od. It will be awesome! And it has potential for future growth with an SBM.
Click to expand...
This is the direction I am leaning now. And try it for awhile with the 3.91s and then decide if a lower rear gear might be better.
 
Just to reiterate A FD of 2.50 is about as low as the 340 will handle fuel-economy wise, and second gear with the 3.91s is perfect for street work. I know I would love that combo.........................................with a 360 especially.
I think it's also worth mentioning, that for your stated useage, I/personally, would swap out the factory cam in a heartbeat, for one or two sizes smaller with a tighter LSA, and go with one or two sizes smaller rear gear. My actual thinking is a 262/270/108 in at 106....and 3.55s
And here's why;
The smaller intake duration will normally reduce power, but in this case the 108LSA will tend to maintain the original 268* absolute power. The tighter LSA will reduce the powerband some, but the new trans doesn't care, the ratios are much closer together. So; so far, it's a breakeven thing.Then first consider that the earlier closing intake will increase the Dcr about .4, so making additional low-rpm power over the 268. Now, consider the exhaust cycle the 262 has plus 11* of power extraction. This will very significantly decrease your fuel consumption. Those 11* represent 10.6% additional time to extract energy from the expanding gases. So now we're winning. Then consider the overlap; the 262 has 6 extra degrees so it's almost a wash. Without headers it won't make a significant power difference. So at least we're not losing.
But now it gets interesting; this new cam, say it has the same rates of lift as the old one; The VP will climb from about 126 with the 268 to about 142 with the new one.But don't look at the absolute numbers, but rather at the percentage difference, which is PLUS 12.7% for the 262. It won't matter what the actual numbers work out to, but the percentage is what you're interested in. This VP number is an indicator of low-rpm performance. And I can tell you that 12.7% is huge at just off idle. The VP ratio tapers off so that by somewhere between 3000 and 4000 the percentage difference may no longer exist. But considering that every time you leave the stoplight, that extra torque is making your 340 feel like it's 12.7% bigger. A high VP is a good thing. You can read about VP here; Cam Timing vs. Compression Analysis
The other thing about the VP is that you can reduce your rear gearing by a like amount and feel no low-rpm change as compared to with the 268. So that lets you run a 3.91 less 12.7% which rounds to 3.55s. And now you can see where I'm going. 3.55 x .68= 2.41 final drive, bringing your hiway Rs down to 65=1946 and 80=2395 (both with 27s). And now that power extraction is working together with the gears to increase your fuel economy. The difference in Rs is the difference in the rear gears or about 10%. Generally this translates as 5% more mpgs. But with the extra power extraction, I predict an even greater gain. Now if you have a TQ,or a carb with metering rods, you will be able to easily lean out that low-speed circuit and add a bunch of timing with the Vcan, and before you know it, you'll be passing every gas-station in sight.

So let's recap;
A close ratio trans with a deep enough first gear,a smaller cam, and less gear.
Compared to the current combo,this may result in : no loss of take-off power, no loss of acceleration to 60mph;Still in second at the 60mph mark but now right on the power-peak (so actually might be quicker),, less NVH at cruising speed (any cruising speed),and better fuel economy. Finally perhaps a slightly lopier idle, but that will depend on the tune.
And now for the icing; With a faster rate of lift,(The OEM was pretty good, but faster exists), you could keep the 262 but it can make another 10 to perhaps as much as 20 horsepower at peak, and with the 108LSA that would feel really fine,lol, and it will blast thru the gears quite a bit better, with the close-ratio trans.
There is only one fly in the ointment;the current compression ratio. If your Scr is currently more than a true 10/1 then it may be that you have to run a top-grade fuel when standing on it. Probably only when the secondaries are full open, at too low an rpm. This can be mitigated with a careful tune. But I'm willing to bet your Scr is not over 10/1, or at least not by much. A careful compression test with a good quality gauge will tell the tale.
And then there's 3.73s,lol. 5% more everything, including about 100rpm at 65mph. Hmmmmmmmmmmmmmmm that could be about 20ft lbs at peak, and maybe 10 at take-off. Hmmmmmmm that's about one cam size at thru the powerband; kindof the best of both worlds. That's also about equal to the fast rate cam. But it will steal a bit of mpgs. Cruise rpm now up about 100rpm at 65..........naw I think it could be a wash.

That's my thinking
 
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AJ/FormS said:
Just to reiterate A FD of 2.50 is about as low as the 340 will handle fuel-economy wise, and second gear with the 3.91s is perfect for street work. I know I would love that combo.........................................with a 360 especially.
I think it's also worth mentioning, that for your stated useage, I/personally, would swap out the factory cam in a heartbeat, for one or two sizes smaller with a tighter LSA, and go with one or two sizes smaller rear gear. My actual thinking is a 262/270/108 in at 106....and 3.55s
And here's why;
The smaller intake duration will normally reduce power, but in this case the 108LSA will tend to maintain the original 268* absolute power. The tighter LSA will reduce the powerband some, but the new trans doesn't care, the ratios are much closer together. So; so far, it's a breakeven thing.Then first consider that the earlier closing intake will increase the Dcr about .4, so making additional low-rpm power over the 268. Now, consider the exhaust cycle the 262 has plus 11* of power extraction. This will very significantly decrease your fuel consumption. Those 11* represent 10.6% additional time to extract energy from the expanding gases. So now we're winning. Then consider the overlap; the 262 has 6 extra degrees so it's almost a wash. Without headers it won't make a significant power difference. So at least we're not losing.
But now it gets interesting; this new cam, say it has the same rates of lift as the old one; The VP will climb from about 126 with the 268 to about 142 with the new one.But don't look at the absolute numbers, but rather at the percentage difference, which is PLUS 12.7% for the 262. It won't matter what the actual numbers work out to, but the percentage is what you're interested in. This VP number is an indicator of low-rpm performance. And I can tell you that 12.7% is huge at just off idle. The VP ratio tapers off so that by somewhere between 3000 and 4000 the percentage difference may no longer exist. But considering that every time you leave the stoplight, that extra torque is making your 340 feel like it's 12.7% bigger. A high VP is a good thing. You can read about VP here; Cam Timing vs. Compression Analysis
The other thing about the VP is that you can reduce your rear gearing by a like amount and feel no low-rpm change as compared to with the 268. So that lets you run a 3.91 less 12.7% which rounds to 3.55s. And now you can see where I'm going. 3.55 x .68= 2.41 final drive, bringing your hiway Rs down to 65=1946 and 80=2395 (both with 27s). And now that power extraction is working together with the gears to increase your fuel economy. The difference in Rs is the difference in the rear gears or about 10%. Generally this translates as 5% more mpgs. But with the extra power extraction, I predict an even greater gain. Now if you have a TQ,or a carb with metering rods, you will be able to easily lean out that low-speed circuit and add a bunch of timing with the Vcan, and before you know it, you'll be passing every gas-station in sight.

So let's recap;
A close ratio trans with a deep enough first gear,a smaller cam, and less gear.
Compared to the current combo,this may result in : no loss of take-off power, no loss of acceleration to 60mph;Still in second at the 60mph mark but now right on the power-peak (so actually might be quicker),, less NVH at cruising speed (any cruising speed),and better fuel economy. Finally perhaps a slightly lopier idle, but that will depend on the tune.
And now for the icing; With a faster rate of lift,(The OEM was pretty good, but faster exists), you could keep the 262 but it can make another 10 to perhaps as much as 20 horsepower at peak, and with the 108LSA that would feel really fine,lol, and it will blast thru the gears quite a bit better, with the close-ratio trans.
There is only one fly in the ointment;the current compression ratio. If your Scr is currently more than a true 10/1 then it may be that you have to run a top-grade fuel when standing on it. Probably only when the secondaries are full open, at too low an rpm. This can be mitigated with a careful tune. But I'm willing to bet your Scr is not over 10/1, or at least not by much. A careful compression test with a good quality gauge will tell the tale.
And then there's 3.73s,lol. 5% more everything, including about 100rpm at 65mph. Hmmmmmmmmmmmmmmm that could be about 20ft lbs at peak, and maybe 10 at take-off. Hmmmmmmm that's about one cam size at thru the powerband; kindof the best of both worlds. That's also about equal to the fast rate cam. But it will steal a bit of mpgs. Cruise rpm now up about 100rpm at 65..........naw I think it could be a wash.

That's my thinking
Click to expand...
This was very interesting to read, at least the parts I understood ha. I do plan to swap cams in the not too distant future and this info will come in handy at that point. By then I hope to have the TKO 600 in and can find one best suited for my setup. As I mentioned, one of the previous owners of my 340 swapped in a Crower cam, but I have no idea what the specs are so I figure it would be best to start fresh with one that I know what I am getting since so much of the tune depends on that.

Thanks again for the information.
 
IMO
Swapping out the cam without giving it chance, is perhaps a bit premature.
You don't actually have to know the cam specs of a previously-installed cam, to know if it's right for you. You just need to drive it for an hour or two, it will become apparent.

Cams come in three flavors 1) too big,ie racey and 2) too small,ie good for fuel economy and torque, and 3) just right, ie street warrior. Within each flavor is a 2 or 3 cam size spread, with perhaps a streeter having an extra one or at most two.
There are only approximately 8 or 9 sizes to choose from all together, running the span from about 240 to 300 in about 7 degree steps. So for economy, one might choose from 240 to 254. And for racing one might choose from 284 to 298 or a bit more for a dedicated guy.
For a streeter we have from 262 to about 284,perhaps 292 for a guy who can make it hook. So that makes a middle of the road street cam about 273. When you go smaller than this, low speed power picks up, and with that comes fuel economy and enough vacuum to operate powerbrakes. When you go bigger than this, high rpm power picks up, fuel economy takes a dump,and the shift-rpm rapidly climbs into the stratosphere, especially with an automatic.
In a specific engine,each cam size will move the power-peak up about 200 rpm, and that is what creates the additional horsepower, cuz as you know, horsepower is a function of torque times rpm. Of course the heads have to support the airflow to make it work.
So choosing a cam should be as simple as choosing the rpm of peak power and grabbing the closest stick that promises to make it happen.
Unfortunately, the engine has to be built to survive the shift rpm. Choosing a cam that power-peaks at 6000, and with a 3 speed automatic, will mean the shift rpm will have to be tickling 7000, and that is a special build to survive.
Building a SBM to survive the occasional blast into the low 6000s by contrast, is relatively tame.
So perhaps a streeter would be wiser to choose a maximum sized cam according to the shift rpm. To that end one might choose 6200, cuz any SBM will survive that as a streeter. That, with an automatic, means a power peak of about 5000 to 5300. And that points directly to the ever-poplar 268* cam, to perhaps,magically, a 273 middle of the road cam,lol. There is a reason that cam is so popular.
A stick car can go one size bigger, cuz the rpm drops at the shift are less. Maybe even two sizes bigger, cuz compression braking will keep the manifold vacuum up during braking to operate the booster, and he's no sitting at the stopite with the engine tugging on the brakes. So that makes 284 about the max for a street SBM with a stick. I say about, cuz ,there's always somebody who swears by the 292,lol.
So that's all well and good, but what about that unknown-already-installed cam. Well there's exactly three things you want to know 1) where is the power peak, and 2) how rapidly does the power fall off,and 3) will my engine survive the trip. And for some 4) does it make enough vacuum to operate my booster for the duration of at least one stoplight.
To find the power peak, you have two or three options. 1)The cheapest is timed runs over; a measured distance,a specific mph range,or a specific rpm range. Not exact, perhaps, but doable and accurate enough for a streeter. 2)And very convenient is the windshield mounted accelerometer. Convenient cuz you can throw any mod on your engine and then run it one time, and see what happened, better or worse.3)and finally,the most expensive is the dyno.
And then there's the combo. The bigger cams rob low speed torque, which can be mitigated with some combination of compression, stall, and gears.

But the simplest of all to see if it suits you,since it's already in there, is just to drive the car.

But I still like post #28
 
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Great info. I definitely will be referencing this if I determine a cam swap would be beneficial.

Like you suggest, I need to get the 5 speed in and drive for a bit and see how I like it before I make that decision.

Thanks again!
 
AJ/FormS said:
The splits are;
600: .66-.68-.78-.64od
500: .61-.68-.75-.68od


The 500 works well with a smaller engine or one with limited torque off idle, or allows about 13% less rear gear.
Say you are a streeter with a stock 268 cam and you love the 3.91s. So your current trans has ratio of 2.66-1.91-1.39-1.00 and splits of .72-.73-.72 . With your current 3.91s the final drive ratios are 10.40-7.47-5.43-3.91. For a streeter, it's the first two ratios that count. That 268 cam wants to be shifted at about 6000 maybe 6100. with the A833. At the shift, the Rs will drop to 72/73% so from 6000 to about 4350, for a powerband of 1650, centered at about 5175. This will get you 60mph @ 5600 with 27" tires, just about perfect for a streeter with a stock 340. So then it follows that you want your new trans to be about the same. So the we take the target 7.47 second gear ratio and divide it by the new second, say 1.98 and you come up with the proper rear gear for it, which is 3.77. Rounded down to 3.73s.
For the TKO 500 with ratios of 3.27, 1.98, 1.34, 1.00, 0.68. Now the new final drives with the 3.73 gear and the 500 are; 12.2-7.39-5.00-3.73-2.54.
Now lets look at those other ratios. The 12.2 is an excellent drag-race starter, and a fabulous first gear for a teener. It's a bit much for a 360 tho. And a 340 is right up the middle. But I like the 61% 1-2 split. Now the hiway gear at 2.54 will bring the Rs up to 80=2524 with 27s. That's pretty sweet. Except the 65 =2050. And the 268 cam is not known to get good fuel economy down there. What I do is rev the engine up in Neutral and measure the rising manifold vacuum. The last RPM when it stops rising, that is the first rpm that the engine is finally becoming efficient. From there it will linger for a while, then begin to drop again.With a 268 cam in a 360 this occurs at about 2200, so 2200 is probably the best cruise-rpm for it. Ima thinking in the 340 the cruise Rs might be about 100 rpm higher. That puts you at a minimum cruise of 2300 in terms of fuel efficiency. And with 2.54s this would be 70mph. So you're in the ballpark.
Then the other two ratios. The 5.00 ratio is good for 98@6100 in the 1/4, and the 3.73 is good for nothing except getting into od,lol. So that's all about the 500. So this is a poor choice for drag racing a stock 340, cuz you never get into 4th. To be able to use 4th, you might need 4.30s and that would kill the starter gear. So bad trade.But it's a great trans for a streeter that hits 98 in the quarter.

Now lets take a look at the 600 which has ratios of 2.87-1.89-1.28-1.0-0.64.
To get the same second gear of 7.47, you'll need 7.47/1.89= 3.95s, rounds to 3.91. Which you already have. So the road ratio are 11.22-7.39-5.00-3.91-2.50..
So the the starter gear will be 3.91 x 2.87=11.22. This is a very nice street starter gear; so we're 2 out of 5.
Next is the cruiser gear; 3.91 x .64= 2.50 and 2200=71 mph just about perfect, so 3 out of 5.
The 5.0 is the same as the 500, and the 3.91s are the same as you currently have. That 5.0 btw is a great passing gear at 60/65 where the Rs will drop right into the peak-torque zone at about 3880
This trans also has better ratios for a streeter going weekend racing, cuz the 4.30s will drive the starter gear to only 4.30 x 2.87=12.34, very nice. (Too much for street IMO, but great at the track). And those same 4.30s are good for 108 at 5800ish. And if you must know,those 4.30s will cruise with a FD of 2.75 which I really like. It makes 65=2220,lol; 80=2730

So you're probably thinking,that I'm thinking,that the 2.87 low is the way to go.... and for a street 340 you'd be right; with anything 3.91 or bigger, that's what I'm thinking.
Click to expand...

I always appreciate your in-depth analysis on gearing. The formulas are always helpful. I was thinking about transmission swaps too, and came to the same conclusion. The close ratio gears seems the way to go. :)
 
demon322 said:
Preparing for a possible 727 to 5 speed swap. I am looking at SST and I was quoted the TKO 600 which has ratios of 2.87, 1.89, 1.28, 1.0, 0.64.

Their other option is the TKO 500 with ratios of 3.27, 1.98, 1.34, 1.00, 0.68.

I am not ashamed to admit that I know next to nothing when it comes to this so any advice would be appreciated. Would the 600 be better for my needs?

71 Demon, 340, 3:91, 28 in rear tire. Most all of my driving will be highway with possibly a track day once or twice a year. I recently swapped an open 3:23 rear for the 3:91 with sure grip. I love the difference on the low end but cruising is pretty brutal at 3k rpm at close to 60 mph.

Thanks.
Click to expand...

So have you spoken to SST about what all is involved in swapping to a TKO transmission? Does the cross member need to be cut? Obviously, the tunnel will since you're an automatic. Are you going with a hydraulic clutch?
 
If you really want to see how those ratios work, graph it out.
On the vertical axis,plot rpm, just 6 equal divisions,( each about 1.5 inches high) along the left side, with zero on the bottom.
On the horizontal,across the bottom, starting from the left side, plot speed in blocks of 10mph,(about 1 inch wide), by using 11 equal divisions, to represent a total of 110 mph. This will fit on a standard 8.5 x 11 sheet.
Then using your chosen rear gear, calculate the speed in each transmission gear at 5000rpm. Next plot those mph results on the 5000 rpm line.Next draw a straight line from each of those points down to the zero-zero corner.And finally, drop short verticals from each point on the 5000line, down to the next closest diagonal line.
You should end up with a sawtooth looking thing,that represents your rpm drop in each gear, from a shift-rpm of 5000.
You can plot as many graphs as you like with different shift-rpms , and using other rear gears.
When you study that graph, you can instantly see at what rpm you will be in any gear, at any speed.
So take a different colored pencil, and plot points for 30 mph in first, and in second. Also plot a point for 60mph on any line that hits about 5000@60 give or take. Also plot 65 mph on the highest gear line.If you have a higher than 65 mpg speed limit, then plot that point also on the top-gear line.Those are your important targets.You can plot additional points that are important to you.
If it doesn't hit the targets you want, make a new graph with a different rear gear, until you hit the most targets, the most satisfactorily.
After that, work it out with the other transmission, to see if it's any better or any worse.
In this way you don't have to take anyone's word for which one is best for you. And you have the best chance of getting the right one for you.
The graphing business also works for automatics, but you have to throw in a fudge factor for convertor slip.
Here is your formula;
MPH= (RPM x TC)/ (1056 x R1 x R2)where;
TC = tire circumference = (Pi x D) and Pi=3.1416. example; a 28"tire is 28 x 3.1416 =87.96
R1 is the differential gear, and
R2 is the chosen transmission gear
The fudge factor for automatics is the convertor slip which is generally assumed to be in the range of 5 to 8 percent. You just subtract that % from the rpm, prior to beginning the calculation. Example for a shift rpm of 5000 I subtract .05 x 5000=250, so Then I enter 4750 in the spot reserved for RPM.
Example
I'll work one out for you, my A833
The ratios are 3.09-1.92-1.40-1.00 ..
The mph points at 5000rpm would be;
For top gear; Mph = (5000 x 88)/(1056 x 3.55 x 1.00) = 117mph
For first gear; Mph = (5000 x 88)/(1056 x 3.55 x 3.09)= 38mph
The in-betweens are 61 and 84
for a procession of 38-61-84-117 So those are the numbers I would plot on the 5000 rpm line.
Have fun!
 
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JoesEdge said:
So have you spoken to SST about what all is involved in swapping to a TKO transmission? Does the cross member need to be cut? Obviously, the tunnel will since you're an automatic. Are you going with a hydraulic clutch?
Click to expand...

They said the torsion bar cross member has to be notched on some installations and that I may not know for sure until the test fit stage. They gave me a diagram to show how to make the cut if necessary and it didn't seem to be too bad. I heard with the 6 speed there is much more cutting involved.

Yes, I plan to go with a hydraulic clutch.
 
Is this is what you would consider to be a NOTCH ??? just be ready for this much surgery.. as you can see my 5 speed isn't
P7010095.JPG
P7010095.JPG
PC010014.JPG
as large on top as a TKO.

PC010015.JPG
 
LJ67barracuda340 said:
Is this is what you would consider to be a NOTCH ??? just be ready for this much surgery.. as you can see my 5 speed isn'tView attachment 1715099569 View attachment 1715099569 View attachment 1715099570 as large on top as a TKO.

View attachment 1715099571
Click to expand...
Oh wow! No that is definetly more than a notch! Did you have to weld some material back if for support?

The finished product looks very good. Have you been happy with the 5 speed?

This was the notch that they said some cars require

20CC7AD7-6150-4C01-A1A5-CB6AC0BC4E12.jpeg
 
I boxed in the cross member open ends and welded the remaining cross member solidly to the floor (instead of just the spot welds). My plan was to have the shifter come out of a factory console with a factory looking shifter in the original place. Although I got my LGT 700 from Keisler just before they went away, I needed some support after it was in, in the way of what parts it took. Silver Sport wouldn't help, Legend Gear wouldn't help (we don't deal with the public), Bowler Transmission no help, Jody's Transmission (oh we've never had one of those apart, don't know.)
Yes I'm happy with having the 5 speed and the MAN peddle behind my 400 HP 340 but the aggravation was high for quite a while.
Back to your ratio question,,, IMO don't get a low first ratio,, you'll be shifting at the first cross walk with the 3;91's
My #'s are 2.66/1.78/1.30/1.0/0.69 with a 3.23 rear for now. It pulls hard with 2.45/60/14's, that's barely enough tire. 105 kmh /65 mph = ~ 1900 rpm I think. I built a torque motor and the splits seem about perfect with the close ratios.

PA270529.JPG


PA270532.JPG
 
LJ67barracuda340 said:
I boxed in the cross member open ends and welded the remaining cross member solidly to the floor (instead of just the spot welds). My plan was to have the shifter come out of a factory console with a factory looking shifter in the original place. Although I got my LGT 700 from Keisler just before they went away, I needed some support after it was in, in the way of what parts it took. Silver Sport wouldn't help, Legend Gear wouldn't help (we don't deal with the public), Bowler Transmission no help, Jody's Transmission (oh we've never had one of those apart, don't know.)
Yes I'm happy with having the 5 speed and the MAN peddle behind my 400 HP 340 but the aggravation was high for quite a while.
Back to your ratio question,,, IMO don't get a low first ratio,, you'll be shifting at the first cross walk with the 3;91's
My #'s are 2.66/1.78/1.30/1.0/0.69 with a 3.23 rear for now. It pulls hard with 2.45/60/14's, that's barely enough tire. 105 kmh /65 mph = ~ 1900 rpm I think. I built a torque motor and the splits seem about perfect with the close ratios.

View attachment 1715099800

View attachment 1715099801
Click to expand...
Nice. Sorry you had so much trouble getting support/parts for the install. Looks like it worked out in the end.

Thanks for those pics! I have the same console now and wanted to keep it, so it was neat to see your setup. I'm hoping to just be able to swap my auto top plate out for a 4 speed one and a boot and that part should fit.
 
LJ67barracuda340 said:
I
My #'s are 2.66/1.78/1.30/1.0/0.69 with a 3.23 rear for now. It pulls hard with 2.45/60/14's, that's barely enough tire. 105 kmh /65 mph = ~ 1900 rpm I think. I built a torque motor and the splits seem about perfect with the close ratios.
Click to expand...

I agree those splits are pretty nice for a 340....67-.73-.77-.69od. Very nice progression.
I am somewhat surprised tho that you're not complaining about the lack of starter gear, or the fuel mileage at 65=1900rpm,lol. I'm guessing if NA that you're running a fairly stout cam,and or some mean heads,lol. With just an 8.59 starter, I'd have to guess heads?
 
AJ/FormS said:
I agree those splits are pretty nice for a 340....67-.73-.77-.69od. Very nice progression.
I am somewhat surprised tho that you're not complaining about the lack of starter gear, or the fuel mileage at 65=1900rpm,lol. I'm guessing if NA that you're running a fairly stout cam,and or some mean heads,lol. With just an 8.59 starter, I'd have to guess heads?
Click to expand...

So what range is a good starter gear?

I think I like it high, just so I can put it in first gear and chug along while idling in bumper to bumper L.A. freeway traffic. I can't do that with my 2.66 first and 3.23 rear. :( It starts to buck if I try.

As an example... My '16 Tacoma has a 3.98 first gear and 4.30 rear gears. I can idle in first gear at 3 MPH. Perfect for freeway bumper to bumper traffic! Of course, the tires are much taller than the Duster though. I'm sure fuel injection helps too.
 
A to a starter gear
This is usually a compromise. First is the easiest to compromise cuz your usually just passing thru it on the way to somewhere else.
With a 4-gear
At the race track trapping in the right gear at the right rpm gets usually the lowest ET, so you gotta do what you gotta do, and first-gear is what it is
For a streeter second gear is usually the one to bias for, and since we really only have two low,s to choose from, again The starter gear gets compromised. I like to be dogging it at 30/35 in second gear, but have enough TM to keep up with traffics ups and downs. Shifting back and forth gets old. At the same time,when I backshift into first, I want the car to launch into next week! So I normally it's hard to do both. Then you add in cruising at a reasonable rpm, and it's all but impossible, to get a decent starter gear.
As to the engine
The more cubes you have or the smaller the cam, actually it's the VP that is of interest,, but the more VP you have, then the easier it is to get moving with a less than ideal starter gear.
And that is why I have a 367 with 10.9 Scr, and why I used to have a 223/230/110 cam. This combo gave me enough VP for a killer take off with a crappy starter gear. But when that cam died, I got greedy and installed a 230/237/110, and immediately I could feel the loss of VP. And that is when I began the hunt for the right starter gear. I eventually found it in a combination of trans,rear, and od.
So for me, it ended up with The 3.09-1.92-1.40-1.00-.78od and 3.55s This hit the most targets. This makes a starter of 10.97. This is pretty good making 4mph at 545rpm, walking speed. Of course the engine didn't like 545 with that 230 cam, so I had to work on that.But eventually I got her banging away reasonably happy. So for me the 10.697 is the bare minimum, cuz it makes 4 mph,doable. ZAnd it sets me up at 32 mph=4400rpm, ready to blast off,yet 32 is 2700 in second,reasonably quiet . and not sounding pretentious.and it sets me up for 93=5750 in third gear. And it sets me up for 65 =2870in fourth,and 65= 2236 in overdrive.So I'm hitting all the targets. With a 4+1.

So that brings us to 5-speeds
With a 5 you can hit more targets with less compromises.
To begin with there is about a 20% difference from trapping best in the 1/8 to trapping at the best in the qtr. so if your 4-5 split is neat 80% that's approaching perfect. Notice that LJ340 has a 3-4 split of 1/1.3=.77 which is close to perfect. And so with the right rear gear, he's all set to go racing, either venue, whereas the rest of us are swapping chunks or trapping off rpm.
Well it turns out that trapping at 112in the qtr usually takes 4.56s, or thereabouts. And so he's got a starter of 4.56 x 2.66=12.13 which is also pretty ideal for a track-car.
And finally he has a final drive ratio of 3.146 to cruise home at 65=2540 So,all-in-all a great combo, for a 340 with enough power to like 4.56s.
But if he only has power enough to like 4.88s then we are getting too much starter gear as a DD, and the hiway cruise is starting to buzzzzzzz.
But if he has a bit more power and can run 4.30s, Then the tranny is working better as a streeter, with only a little compromise as a streeter, so that's a good deal. But to really use those 4.30 that 340 is gonna be a bit of a brute on the street, or the chassis is gonna have to be lightened..4.30s are for cars that run closer to 120.

So now let's talk about your combo. What are your targets? Did you make any of those drawings yet? Re post #34
The typical starters are from 8.59 to 10.94, a spread of 27%. These represent 3.23s to 4.10s and the 2.66 low gear. you can fit just about any SBM streeter into there somewhere.
So,it turns out that there is about a 5 cam spread for a stick-shift streeter, running from 252 to 292. Middle of the bunch is about 272 then. If the Dcrs are well matched, then I'm gonna say a fun starter for a 340 is 9.77ish,right up the middle. This is a 2.66 x 3.73s for anyone following along. Now if you have a smaller cam or more cubes, you can go less. But a bigger cam or smaller cid, is gonna want more.
And if your Dcr is in the basement, then any combo is gonna want more starter.
I know my combo would be happy with 9.77 right up the middle..And I have a 367 with a 276 cam; so that would be right where the prattle predicts me to be.
 
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demon322 said:
Nice. Sorry you had so much trouble getting support/parts for the install. Looks like it worked out in the end.

Thanks for those pics! I have the same console now and wanted to keep it, so it was neat to see your setup. I'm hoping to just be able to swap my auto top plate out for a 4 speed one and a boot and that part should fit.
Click to expand...
no problem,, my issue with the parts wasn't with install, it was about a noise we heard after it was running. We (the local trans shop) thought after remove and disassembly thought it needed a 1st gear bearing and I needed some specs on clearances. No one would help with some info. Since it is supposed to be a redesign of a T56 we installed a bearing from a Viper trans from Mopar. I'm just pissed that we had to wing it with no support from anyone. My console is an auto with a 4 speed top plate like you want to do. I did have to send the trans back to Tenn from Canada to have the shift mechanism relocated to be directly under the hole in the rubber boot, so you have to watch for that. When I got the "perfect fit trans" the shifter was coming thru the ashtray. Hence the aggression.
 
AJ/FormS said:
I agree those splits are pretty nice for a 340....67-.73-.77-.69od. Very nice progression.
I am somewhat surprised tho that you're not complaining about the lack of starter gear, or the fuel mileage at 65=1900rpm,lol. I'm guessing if NA that you're running a fairly stout cam,and or some mean heads,lol. With just an 8.59 starter, I'd have to guess heads?
Click to expand...
your pretty close,,,It starts real nice,,
340 +.030, 10.1 cr, flat tops zero deck, .039 quench, roller 222/226 @ .050, .550"/.548" with 1.6 rockers, Eddl RPM's closed chamber, Air Gap and FiTech,,, 21.59 MPG cruising with one dig with a Jeep GC SRT8,,,I'm satisfied but looking for more of course.!!!
 
LJ67barracuda340 said:
your pretty close,,,It starts real nice,,
340 +.030, 10.1 cr, flat tops zero deck, .039 quench, roller 222/226 @ .050, .550"/.548" with 1.6 rockers, Eddl RPM's closed chamber, Air Gap and FiTech,,, 21.59 MPG cruising with one dig with a Jeep GC SRT8,,,I'm satisfied but looking for more of course.!!!
Click to expand...

Oh, I shoulda guessed roller. That'll bump your VP up and make your starter-gear bearable.

I ran a practically identical combo but on a 360 base, and no roller. That was a dynamite combo, and by far my favorite. I ran it with 3.55s and no EFI. So practically identical,lo. At least from the decks to the top of the intake.

But as to your combo, I think as a streeter the engine is pretty much optimized. I guessed that roller was a 262 advertised, and that might look like this
Static compression ratio of 10.2:1.
Effective stroke is 2.72 inches.
Your dynamic compression ratio is 8.55:1 .
Your dynamic cranking pressure is 174.25 PSI.
V/P (Volume to Pressure Index) is 148.............................................148

So the next bigger cam would drop your Dcr and VP
Static compression ratio of 10.2:1
Effective stroke is 2.66 inches.
Your dynamic compression ratio is 8.38:1 .
Your dynamic cranking pressure is 169.79 PSI.
V/P (Volume to Pressure Index) is 141............................................141
It doesn't look like much on paper, but Everything is going in the wrong direction.
Your heads and Q will accept over 9/1 Dcr and still run pumpgas. I ran 8.9Dcr/11.3Scr on 87E10 for about 8 months, then tore my 367 down for inspection. She was good to go back together. Others here have said they also run over 9/1Dcr.and over 200 psi.So your current combo is about right.
The Dropping VP is a little concerning to me. I swapped out that [email protected] for a [email protected], just one cam size difference, and lost 9 points of VP, and I could really feel it. I was already running 3.55s, and no overdrive, so I had to do something. My solution .....eventually, was to get a 3.09 low box AND an overdrive, and still the 3.55s. That restored my take off power, and reduced my cruise rpm simultaneously. I found the same thing when going from the 292/108 Mopar cam, to a 270/110 Hughes cam, again of 19 points of VP, at close to the same Dcr. That is what I expected, and it was awesome. I swapped out the 4.30s that the Mopar cam liked, back to the 3.55s. which the Hughes liked.
What I learned was that 19 points of VP was worth 21% gear. And 9 points was worth 10% gear.
So knowing that,now, I can confidently say that in your combo, the 7 point change in VP is gonna demand a 7% increase in gear. That comes to 3.46 and rounds to 3.55s.
VP is just a measuring stick to help predict low rpm performance. Which, IMHO, is pretty important for a streeter.Cuz we spend most of our time in that Zone. You for instance, with 3.23s can take those, to 28mph @3000rpm. Then you shift and will be in second at 2000. So that's all lowrpm stuff. You better have some VP there to pull away cleanly.
On the other hand the next bigger cam would move your power peak up about 200rpm, and with that and the Eddies, you'll pick up about 20 horsepower...... at 5200rpm. That's a nice kick at 44mph with 3.55s. Of course the power begins increasing at maybe 3000/25mph in first, but you're not likely to begin feeling it until 4400/38mph still in first.
SO IMO, if you have to buy gears anyway, to take advantage of that bigger cam, you might as well do that first. And with the .69od you might as well optimize them for the current cam. And when you do that, man that 340 is gonna jump! So then you will forget all about more cam for a few years.
So what gears?
Well it depends on what you're gonna do with the car. I can tell you my opinion and you can take it from there.
With a VP of about 148, (remember I had a 143 that liked 4.30s), and the .69od, IMO, 3.91s would be the minimum with a 2.66 low. That will get you a starter gear of 10.4, which is 21% more TM than current. That's a lot of additional jump. I currently run a 10.97 starter with a VP of 153. It's a little more than I need, so it'll be just right for you. Your cruize rpm will still be pretty good at 65=2180. I run 2240 and am very happy with that. So now you have both ends covered. From here you can let those fabulous splits fill in the blanks.
Now you should know that those 3.91s are gonna let your 340 buzz up to the shift rpm pretty quick. What that means is she'll be putting down more average HP per unit of time than she currently is. And that means a lower zero to sixty time. And those 3.91s are gonna let you hit 60 at 5200 just about where your current combo is peaking. You could run a little more gear, but 4.10s will jump your cruize rpm up about another 5%.
To recap; slam some 3.91s in there and never look back. Probably less than $500 installed. Maybe tighten up your SureGrip while it's out.
So that's my opinion, and it's on the cheap.

OK wait, if your still not sold,Here's another argument;
Say your engine makes 400 peak ftlbs and your trans multiplies that by 2.66 and your rearend multiplies that by 3.23. And lets ignore any powerloss thru the gears for now. That totals 3437ftlbs at peak.
Well with the 3.91s it totals plus 21% or 4160. That maths out to an additional 723 ftlbs. And every single gear will show the same 21% increase.
At the torque peak say 3900rpm, this will feel like 400 x 21% x 3900 /5250 =62 more hp. That's about triple of what just one cam size will feel like, with the 3.23s.
Case closed.
 
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