A-833 2.47 1st gear change to 3.09
- Thread starter go-fish
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AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
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I have the Commando and 3.55s. Take-off is a dump-it and go deal.
That is to say, with the factory heavy flywheel, with a gentle blip on the throttle, I can just dump the clutch, no gas given, and the car will motor ahead at anywhere from 3.5 to 4mph depending on where I have the Idle-timing set on my dash-mounted, dial-back, timing device..
However, My engine is set-up at 11.3 Scr and pumps over 185psi. It will willing idle, and pull, at just 5* of Idle-Timing. and it will easily take throttle with no bucking, no hesitation, no flatspots, no tip-in sag. That is what the difference from low-pressure to 185psi, can do for you.
At the other end I cruise with the GVod at 65=2240 rpm, with the Cruise-timing set to about 53*, and the throttle barely open.
This combo would be fine with the 2.47 box and 3.91s and the overdrive, but, the cruise rpm would jump to 2470. Second gear would be 6.92, compared to my current 6.82, so Second gear would feel exactly the same. But with the close-ratio T/A trans and 3.91s, blasting thru the gears was insane!, lol.
I traded that T/A for a 3.09 od box straight up, so I could split gears with the GVod
My new ratios were;
3.09-2.41-1.67-1.30-1.00-.78od-.55od, yes SEVEN useable gears. and 65=1550rpm/85=2030
Check out the splits; .78-.70-.78.-.77-.78-.71
With over 350hp on tap, this was outrageous. and I ran it like that for 4 years, with rear gears up to 4.88s. Finally I realized that 7 gears was at least two too many for a street car, and 1550 was too low an rpm to cruise at for economy with a 223/230/110.
So when that cam dropped lobes, I went to the next bigger, and dropped in the Commando/GVod. Now I have 5 progressive gears with the option of splitting 2 more. However, the new cam makes enough power to go 93 in the Eighth, splitting the first two gears, and so, fuel economy sortof took the backseat. and the cylinder pressure took a lil hit.
Some people think that a .78 overdrive gear is hardly worth bothering with, bit first off , with 3.55s the cruise rpm ratio becomes 2.77, and 65= 2240rpm. and
Secondly, I shift into od after third, so my ratios are
3.09-1.92-1.39-1.09-.78od, and so the splits are;
.62-.73-.78-.72od, so in this way, .78 becomes .72, about on par with the best of the rest; and I really like the short 3-4.
what I like to do when hitting the hiway, is to rev it to just 2800/3000 in each gear. This brings me to 62mph in third over, and then I drop it into 4th over, and lazily bring it to 65mph, and when I get there, I crank in some more timing, from the driver's seat.
Then, at 2240, and 53* of timing, I know the fuel-economy is gonna be the best that it can be. On long trips, I dial in up to another 10 degrees, depending on if she likes it or not. Alloy heads seem to love cruise-timing.
I'm not bragging on the combo, I'm just telling you what I did.
and btw with double overdrive and that smaller cam, on one non-stop day-trip, point to point fuel economy hit 32mpg US.
Now some guys will decry that, and again, I'm just telling you what I did, and it was common for that combo to sail that deep.
Your cam has the potential to get close to that, but the fuel-economy is in the complete combo, which in my case included a 3.58 stroke, and pressure pushing 195psi. IIRC.
That is to say, with the factory heavy flywheel, with a gentle blip on the throttle, I can just dump the clutch, no gas given, and the car will motor ahead at anywhere from 3.5 to 4mph depending on where I have the Idle-timing set on my dash-mounted, dial-back, timing device..
However, My engine is set-up at 11.3 Scr and pumps over 185psi. It will willing idle, and pull, at just 5* of Idle-Timing. and it will easily take throttle with no bucking, no hesitation, no flatspots, no tip-in sag. That is what the difference from low-pressure to 185psi, can do for you.
At the other end I cruise with the GVod at 65=2240 rpm, with the Cruise-timing set to about 53*, and the throttle barely open.
This combo would be fine with the 2.47 box and 3.91s and the overdrive, but, the cruise rpm would jump to 2470. Second gear would be 6.92, compared to my current 6.82, so Second gear would feel exactly the same. But with the close-ratio T/A trans and 3.91s, blasting thru the gears was insane!, lol.
I traded that T/A for a 3.09 od box straight up, so I could split gears with the GVod
My new ratios were;
3.09-2.41-1.67-1.30-1.00-.78od-.55od, yes SEVEN useable gears. and 65=1550rpm/85=2030
Check out the splits; .78-.70-.78.-.77-.78-.71
With over 350hp on tap, this was outrageous. and I ran it like that for 4 years, with rear gears up to 4.88s. Finally I realized that 7 gears was at least two too many for a street car, and 1550 was too low an rpm to cruise at for economy with a 223/230/110.
So when that cam dropped lobes, I went to the next bigger, and dropped in the Commando/GVod. Now I have 5 progressive gears with the option of splitting 2 more. However, the new cam makes enough power to go 93 in the Eighth, splitting the first two gears, and so, fuel economy sortof took the backseat. and the cylinder pressure took a lil hit.
Some people think that a .78 overdrive gear is hardly worth bothering with, bit first off , with 3.55s the cruise rpm ratio becomes 2.77, and 65= 2240rpm. and
Secondly, I shift into od after third, so my ratios are
3.09-1.92-1.39-1.09-.78od, and so the splits are;
.62-.73-.78-.72od, so in this way, .78 becomes .72, about on par with the best of the rest; and I really like the short 3-4.
what I like to do when hitting the hiway, is to rev it to just 2800/3000 in each gear. This brings me to 62mph in third over, and then I drop it into 4th over, and lazily bring it to 65mph, and when I get there, I crank in some more timing, from the driver's seat.
Then, at 2240, and 53* of timing, I know the fuel-economy is gonna be the best that it can be. On long trips, I dial in up to another 10 degrees, depending on if she likes it or not. Alloy heads seem to love cruise-timing.
I'm not bragging on the combo, I'm just telling you what I did.
and btw with double overdrive and that smaller cam, on one non-stop day-trip, point to point fuel economy hit 32mpg US.
Now some guys will decry that, and again, I'm just telling you what I did, and it was common for that combo to sail that deep.
Your cam has the potential to get close to that, but the fuel-economy is in the complete combo, which in my case included a 3.58 stroke, and pressure pushing 195psi. IIRC.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 25,159
- Reaction score
- 12,515
BTW
the 3.09 low gear trans, is a completely different gearset. IIRC ONLY the low-gear will swap with a 2.66 box.
Furthermore from 2.66 to 3.09 is plus 16%, which is the same as from 3.23s to 3.73s, without the wide 1-2 split.
With a high-compression 360, that split is no bother. But the smaller your engine is, or the the less it's CCP, or the lower the cruizer gear, the more annoying that split gets to be. As these begin to come into play, you will find yourself revving it higher and higher in First, before shifting into Second gear, thus sounding more and more like a Mustang. and
if there's one thing I hate,
it is sounding like a Mustang.
Having said that;
my combo has run every 1x23 trans, and just about every rear gear from 2.76 to 5.13s, in search of the perfect ratios, and three different cams with various pressures from a low of 177 to a high of 195, to find the perfect combo; and I found it in 2004.
It was the Commando with the GVod, and with 3.23s.
But, my car traps better with 3.55s and the zero to sixty runs better in First-over, with 3.55s, so 3.55 is what I have run ever since.
Happy HotRodding.
the 3.09 low gear trans, is a completely different gearset. IIRC ONLY the low-gear will swap with a 2.66 box.
Furthermore from 2.66 to 3.09 is plus 16%, which is the same as from 3.23s to 3.73s, without the wide 1-2 split.
With a high-compression 360, that split is no bother. But the smaller your engine is, or the the less it's CCP, or the lower the cruizer gear, the more annoying that split gets to be. As these begin to come into play, you will find yourself revving it higher and higher in First, before shifting into Second gear, thus sounding more and more like a Mustang. and
if there's one thing I hate,
it is sounding like a Mustang.
Having said that;
my combo has run every 1x23 trans, and just about every rear gear from 2.76 to 5.13s, in search of the perfect ratios, and three different cams with various pressures from a low of 177 to a high of 195, to find the perfect combo; and I found it in 2004.
It was the Commando with the GVod, and with 3.23s.
But, my car traps better with 3.55s and the zero to sixty runs better in First-over, with 3.55s, so 3.55 is what I have run ever since.
Happy HotRodding.
DionR
Well-Known Member
FWIW, my A833OD first to second drop is significantly worse than the 1st to 2nd drop with the 3.09:1/1:1 gear set, and I run a low compression 360. And I don't find that I have to rev it to the moon before I reach for second. I just drive it and it feels fine.
For comparison sake, my 360 has rebuilder pistons from about 1991 and they are about 1/8" in the hole. Even with the smaller combustion chambers of the MP R/T heads, I figure I am only 8.5:1. And my cam is a regrind from Bullet with 262/267 or 206/210 @ 0.050. The thing needs more compression and yet it drives fine for me.
For comparison sake, my 360 has rebuilder pistons from about 1991 and they are about 1/8" in the hole. Even with the smaller combustion chambers of the MP R/T heads, I figure I am only 8.5:1. And my cam is a regrind from Bullet with 262/267 or 206/210 @ 0.050. The thing needs more compression and yet it drives fine for me.
Yeah, if memory serves, the OD 4-speed goes from 3.09 low to 1.67 second. The direct drive goes from 3.09 to 1.91.
3-speed manuals of various makes/years typically go something like 2.5 low to 1.5 second. Less of an rpm drop than the OD 4-speed, more than the 3.09 direct drive 4-speed.
By the way, the old GM close ratio 4-speeds had a 2.20 low gear. To get a 9.98 overall low gear ratio with those trannies, you needed 4.56 rear gears. And lots of people thought the close ratio GM 4-speed was the hot setup. Not without some pretty steep rear gears, though.
??? Unless I'm missing something, a 3.09 low gear would need to mesh with a counter shaft for a 3.09 low gear. A 2.66 counter shaft wouldn't work. So unless the other three gears were the exact same ratios, the other gears from a 2.66 trans likewise wouldn't mesh with a counter shaft for the 3.09 low gear trans. At any rate, my memory is that the entire gear set and countershaft in my later trans case are from my original 65 Barracuda trans.
DionR
Well-Known Member
Based on the chart in post #20, first gear on the mainshaft is the same as the 2.47 and 2.66 gearset. But 2, 3, input and cluster gear are all different. Maybe that's what he meant?
OK, been a while since I've been in one, or examined how the power is transmitted through the trans, but I vaguely remember that in low gear, the first gear locks onto the counter shaft, goes to the rear down to the most rearward gear on the counter shaft and up into the main shaft. So the first gear can be the same for different low ratios because the rearmost gears on the counter shaft and main shaft are different for the different trannies, giving each trans different low gear ratios with the same number of low gear teeth.
What I call the counter shaft and the chart calls the cluster gear is specific to each transmission. The low gear is interchangeable in several, but just changing that won't change the actual low gear ratio.
Did I figure that right?
Have to say I never knew the same low gear was used in different transmissions with differing low gear ratios.
Newbomb Turk
Well-Known Member
Kind of.
Every gear but 4th goes through the input (4th gear) the cluster gear.
When you put the box in first it goes through the input, over to the cluster, up the cluster and over to first where it goes out the output.
There are a few gears that interchange but the clusters are different.
Probably should go look at the book to verify but I’m pretty sure I have the gears stuff correct.
DionR
Well-Known Member
I seem to remember Passon's book saying something about the early and late OD gear set's not being interchangeable even though the tooth count was the same. I kind of doubt the non-OD gearsets have the same issue, but it made me pause.
perfacar
Well-Known Member
when you change ratios, you change everything, 1 st ,2nd , 3rd gears, cluster, input shaft, you don't change reverse gear. some gears show same tooth count, but are different dia, won't fit. you can't mix and match gears, all are specific to each ratio set.
Dale Davies
Well-Known Member
For first gear selection I use a combination of trans X final = about 10 to 1. So if you want good fuel economy and quiet operation on the hiway, you would choose a taller final drive to keep the RPM down. That then requires a lower first gear.
A few years ago, BMW was using fairly tall final drive ratios with low first gears in the transmissions. The transmissions used 4 to 4.3 first gear combined with a 2.5 to 2.8 axle ratio. The thinking was there is less frictional loses with a 1:1 trans top gear and a high final drive, than using a lower final drive with OD.
Newer Mustangs use a Tremec trans with 2.66 or 2.87 first gear and 3.55 or 3.73 final drive. There is two OD ratios. The General in the Camaro uses the same model trans but with a taller final drive, 4.03 first and the OD is not as tall. In the Cadillacs using the same trans, the final drive is taller with a 4.3 first gear and one OD of 0.8.
Hyper_pak
Old School Chrysler Fan
To the OP, where are you located?
I have 2 or 3 main cases that I would like to sell.
I am in Texas south of DFW.
I have 2 or 3 main cases that I would like to sell.
I am in Texas south of DFW.
Newbomb Turk
Well-Known Member
Any chance you have an A body big output spline main shaft laying around you’d like to part with??
PM me if you have a critter like that.
Hyper_pak
Old School Chrysler Fan
No I bought my last one from Brewers.
I had to build a 2.47 trans and needed one myself.
He sold one one that was not prefect but plenty good for a very fair price.
Spudmaster
Well-Known Member
Spudmaster
Well-Known Member
Check to see if you are having the front brakes hanging up after you release them. I had this problem on my Valiant and is was sluggish off the line. Fixed it and it’s great now.
My OEM disc brakes were good and I recently put a Cordoba set up on it and they work even better.
This thread was always about gear ratio options for my 23 spline A833. Specifically 1st gear.
The thread is 3 pages and I thought we moved past trying to sell me on 4.10’s, automatics, the tune, engine rebuilds, ….
If anyone is wondering we are currently on track. The responders on page 3 and several others up to now have understood the assignment.
I’m just waiting on Monday to start calling around.
Seems like this is my plan. Going Commando? Of course I’ll seek the wise council of the two major A833 suppliers/specialists.
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