Change from 4-speed to 3w/OD

-
All my833s have been fully synchronized,od or not, as was the A230

But the A745 and A903, three-speeds were not
I think the 230s debuted behind the 340s in the 1970 model, then were the only 3-speed from 71on, or so.

Then it's possible that it is just too big a jump from 1 to 2 and back to do it smoothly speed shifting or down shifting early..........either I don't know why anyone would want to do anyway, considering that the OD transmissions are somewhat weaker. They were built with primarily one goal in mind. Fuel mileage.
 
What it probably amounts to is a combination of factors
1) insufficient clutch departure
2) a tired brass or glazed cone
3) unfamiliarity with the 54% split
4) driving style
5) fear. Fear of taking charge of that shift.

Yes that split is pretty wide, and after you have driven it for a while you learn to blip the throttle, cuz usually the Rs fall faster than you are braking, and the brass cannot increase the engine speed,which may be dragging on the disc, so the operator has to bring it closer to the driveshaft speed, with a little blip, and then whamming the shifter into first. Exactly like driving a graintruck on soft ground; a blip and a wham. But the more familiar you are with this split, the easier it becomes.
The problem is you only have two feet, and one is holding the clutch pedal down. and the other is braking.I think this is partly why 340s had the dashpot on the carb, to slow the Rs down back to idle, so neophytes wouldn't wreck the clutch teeth during the warranty period,lol.
Anyway, what I often do is push the clutch in with power still applied. This causes a little rpm flare, and an easy synchronization. It's just a different driving style.
Also, if you're running lotsa idle timing, you're throttle opening is gonna be pretty small, and when you lift, the engine rpm is gonna tend to drop like a rock,which can make a great compression brake, but it can also make downshifting, a bit of a chore. That's another reason I only run 14*, and also why I kept the stock heavy flywheel.
 
Last edited:
I for one would not want to take charge of the shift. They are not designed for it. That's not fear, that's intelligence.
 
I for one would not want to take charge of the shift. They are not designed for it. That's not fear, that's intelligence.
Well, Rusty, you can drive it your way, and I'll drive it my way, but first gear never wears out first in that box. And my box hasn't been opened now since 2004, And I take charge of all my shifts.
 
Well, Rusty, you can drive it your way, and I'll drive it my way, but first gear never wears out first in that box. And my box hasn't been opened now since 2004, And I take charge of all my shifts.

Well good for you.
 
Then it's possible that it is just too big a jump from 1 to 2 and back to do it smoothly speed shifting or down shifting early..........either I don't know why anyone would want to do anyway, considering that the OD transmissions are somewhat weaker. They were built with primarily one goal in mind. Fuel mileage.

The 833OD’s are fully synchronized just like the regular 833’s. As AJ said, it’s just a big split between gears. You’re shifting between a 3.09 first and a 1.67 second. If you’re not matching rpm’s that means a lot of work for the synchros, they can only do so much. And if you are matching rpms, it might take a little longer to match things up because it’s a big swing, especially dropping revs.

As far as strength, everyone sells the 833OD’s short. No, they’re not quite as strong as a standard 833, but it’s not as big a difference as most people like to think. Most of the components are the same.

What it probably amounts to is a combination of factors
1) insufficient clutch departure
2) a tired brass or glazed cone
3) unfamiliarity with the 54% split
4) driving style
5) fear. Fear of taking charge of that shift.

Yes that split is pretty wide, and after you have driven it for a while you learn to blip the throttle, cuz usually the Rs fall faster than you are braking, and the brass cannot increase the engine speed,which may be dragging on the disc, so the operator has to bring it closer to the driveshaft speed, with a little blip, and then whamming the shifter into first. Exactly like driving a graintruck on soft ground; a blip and a wham. But the more familiar you are with this split, the easier it becomes.
The problem is you only have two feet, and one is holding the clutch pedal down. and the other is braking.I think this is partly why 340s had the dashpot on the carb, to slow the Rs down back to idle, so neophytes wouldn't wreck the clutch teeth during the warranty period,lol.
Anyway, what I often do is push the clutch in with power still applied. This causes a little rpm flare, and an easy synchronization. It's just a different driving style.
Also, if you're running lotsa idle timing, you're throttle opening is gonna be pretty small, and when you lift, the engine rpm is gonna tend to drop like a rock,which can make a great compression brake, but it can also make downshifting, a bit of a chore. That's another reason I only run 14*, and also why I kept the stock heavy flywheel.

Exactly! That’s a big split, you have to match the rpms better because the synchros can’t do everything. They’re not magic, there are limits.

Gotta work on that heel-toe brake/throttle action! :D

I for one would not want to take charge of the shift. They are not designed for it. That's not fear, that's intelligence.

Not designed for it?! That’s exactly how they’re designed!

AJ is talking about matching rpms. That’s exactly how you do it, and it works because that’s how the design of a transmission works. Adjust the engine rpm to get the input speed to match the output speed and the gears slide together. You can do the math with a gear calculator to tell you what the splits are, and when you get familiar with your engine and gear combos it becomes second nature. A blip on the throttle and a firm shift on the lever and away you go! Doesn’t hurt the transmission at all.
 
Ok.

The 833OD’s are fully synchronized just like the regular 833’s. As AJ said, it’s just a big split between gears. You’re shifting between a 3.09 first and a 1.67 second. If you’re not matching rpm’s that means a lot of work for the synchros, they can only do so much. And if you are matching rpms, it might take a little longer to match things up because it’s a big swing, especially dropping revs.

As far as strength, everyone sells the 833OD’s short. No, they’re not quite as strong as a standard 833, but it’s not as big a difference as most people like to think. Most of the components are the same.



Exactly! That’s a big split, you have to match the rpms better because the synchros can’t do everything. They’re not magic, there are limits.

Gotta work on that heel-toe brake/throttle action! :D



Not designed for it?! That’s exactly how they’re designed!

AJ is talking about matching rpms. That’s exactly how you do it, and it works because that’s how the design of a transmission works. Adjust the engine rpm to get the input speed to match the output speed and the gears slide together. You can do the math with a gear calculator to tell you what the splits are, and when you get familiar with your engine and gear combos it becomes second nature. A blip on the throttle and a firm shift on the lever and away you go! Doesn’t hurt the transmission at all.
 
What it probably amounts to is a combination of factors
1) insufficient clutch departure
2) a tired brass or glazed cone
3) unfamiliarity with the 54% split
4) driving style
5) fear. Fear of taking charge of that shift.

Yes that split is pretty wide, and after you have driven it for a while you learn to blip the throttle, cuz usually the Rs fall faster than you are braking, and the brass cannot increase the engine speed,which may be dragging on the disc, so the operator has to bring it closer to the driveshaft speed, with a little blip, and then whamming the shifter into first. Exactly like driving a graintruck on soft ground; a blip and a wham. But the more familiar you are with this split, the easier it becomes.
The problem is you only have two feet, and one is holding the clutch pedal down. and the other is braking.I think this is partly why 340s had the dashpot on the carb, to slow the Rs down back to idle, so neophytes wouldn't wreck the clutch teeth during the warranty period,lol.
Anyway, what I often do is push the clutch in with power still applied. This causes a little rpm flare, and an easy synchronization. It's just a different driving style.
Also, if you're running lotsa idle timing, you're throttle opening is gonna be pretty small, and when you lift, the engine rpm is gonna tend to drop like a rock,which can make a great compression brake, but it can also make downshifting, a bit of a chore. That's another reason I only run 14*, and also why I kept the stock heavy flywheel.
thats exactly how we shift etan-fuller twin counter shaft truck transmissions with no synchronizer's! pulling 80,000 lbs + and not useing clutch once rolling!! ive even seen them speed shifted to but thats more abuse than i could stand way dad taught me!
 
Last edited:
When I said they were not designed for that I was referring to speed shifting. The only 833 actually designed for that was the slick shifted modified transmissions. Even then they can break.

The 833OD’s are fully synchronized just like the regular 833’s. As AJ said, it’s just a big split between gears. You’re shifting between a 3.09 first and a 1.67 second. If you’re not matching rpm’s that means a lot of work for the synchros, they can only do so much. And if you are matching rpms, it might take a little longer to match things up because it’s a big swing, especially dropping revs.

As far as strength, everyone sells the 833OD’s short. No, they’re not quite as strong as a standard 833, but it’s not as big a difference as most people like to think. Most of the components are the same.



Exactly! That’s a big split, you have to match the rpms better because the synchros can’t do everything. They’re not magic, there are limits.

Gotta work on that heel-toe brake/throttle action! :D



Not designed for it?! That’s exactly how they’re designed!

AJ is talking about matching rpms. That’s exactly how you do it, and it works because that’s how the design of a transmission works. Adjust the engine rpm to get the input speed to match the output speed and the gears slide together. You can do the math with a gear calculator to tell you what the splits are, and when you get familiar with your engine and gear combos it becomes second nature. A blip on the throttle and a firm shift on the lever and away you go! Doesn’t hurt the transmission at all.
 
All my833s have been fully synchronized,od or not, as was the A230

But the A745 and A903, three-speeds were not
I think the 230s debuted behind the 340s in the 1970 model, then were the only 3-speed from 71on, or so.
I agree, my 71 slant duster has its 3 speed, fully synchronized.
 
I agree, my 71 slant duster has its 3 speed, fully synchronized.
And my 65 Dart was not. I rarely downshift under power. Roll off the gas, coast down to about 30 and apply the brakes then the clutch not too long after. Too many years driving my tool truck. ( auto trans though) I'm not hard on brakes either.
 
I have 2 iron 833od, one in my 64 dart, I have 355 limit slip 83/4 stock wheels and a built 340 pushing it .
1st gear is a waste and only gets me to 30ish, if I try to power shift it into second the wheels break loose, but it is really hard to shift it into second. Forget about down shifting into 1st it just wont do it. revs are pretty low in overdrive but it lugs if I am going under 40.

Bottom line is it is OK for just cruising around but if you want to have more fun consider something else.
I have purchased a regular 833 and am going to swap it out as soon as I get all of the parts I need, and time to do it.

I was reading thru this thread again trying to resolve what the heck I'm going to do. Is the 833od you have in your 64 the tranny closest to what I'm looking for?
I have 83/4 323's, 360, back tires 215/75R14. How do you think it would do pulling a 10 ft. travel trailer with the 833od?
 
I was reading thru this thread again trying to resolve what the heck I'm going to do. Is the 833od you have in your 64 the tranny closest to what I'm looking for?
I have 83/4 323's, 360, back tires 215/75R14. How do you think it would do pulling a 10 ft. travel trailer with the 833od?
IMO;Not too good; the ratios are too far apart. Unless your 360 was built for torque
The ratios are 3.09-1.67-1.00-.73od. And splits of .54-.60-.73
Lets talk about these splits for a sec. If you take the Rs out to 4000 in each of the first two gears, then the Rs will drop to 2160, and 2400, so your 360 will need some torque down there, to accelerate briskly.
With the 2.66low box having ratios of
2.66-1.92-1.40-1.00, and splits of .72-.73-.71 , the Rs will drop from 4000 to 2880 and 2920. These are fully 33% greater and 21.7%. So just like a hi-stall TC allows your engine to spool up to where there is more power, so also does this 2.66 box allow your engine to remain at a higher power level. So if you already have the 2.66 box, then a straight swap to the od box, while it will launch better, the advantage is lost right at the 1-2 shift. To get any advantage from this box, you need to also change the rear gear.
So lets look at that.
Assuming:
Those tires are 26.7 tall and have a roll-out of ~84", and with 3.23s ,and the od box,and say a torque peak at 3800, and a shift rpm of 4500,
then your speeds at the shifts are 36,66,111,and 152lol. Basically you're asking the engine to pull the load to 66mph with just two gears;then skip direct,and when you drop it into Overdrive the Rs will fall to 1956@66mph. Has your engine got enough torque at that rpm to continue pulling? I venture no. At least not at a small enough throttle opening to be fuel-efficient. So what's the answer?
Well, it might be more gears, so you can use three for acceleration and one for cruising, instead of skipping one.
If you found that your torque monster 360 could get pretty good fuel mileage at 66=2600, then 4.30s would get you that. Shifting at say 4000 now, because you have so much more TM, your shifts would occur at 24,44,74, and 66=3570 in direct, then 2600 in od.Now you are using 2.5 gears to get to 66. With a torque peak still at 3800, you have some passing power and hill-climbing ability in direct. I chose 4.30s because the tooth count is 43/10 and so it is a good strong nearly-impossible-for-you-to-break, ratio... 4.56s would be better but the tooth count is 41/9 and so a bit weaker ratio.

The other option, if that trailer is particularly heavy, or the 360 is weak, would be an early 4 speed; 3.09-1.92-1.40-1.00; and the 3.23s (that you already have). With this "close ratio", now, maybe you can shift at 3800,and your shift speeds would be 30-49-67 and then into direct to cruise at 66=2700. This would be using three gears to pull to 66. Of course passing would be 66=3800 in third gear, bang on the torque peak. The starter gear with this combo is 9.98 so it takes off like a 2.66 box with 3.75s. So it might take a bit of clutch to get moving. 3.55s would be 10% better. I know that doesn't sound like much, but if you had 200ftlbs at 2000rpm then 20 more might allow slipping, from down a couple of hundred rpm. Which means you don't have to rev it up and sound like a Mustang.

With the od box/4.30s,I would run a very small 4bbl. cuz the starter is 13.29, so you will have gobs of take-off power,and the only time you will need a 4bbl is for passing, and you'll be doing about 3200 to 3800,in direct from 60 to 70 mph. Mathematically this requires 417 cfm@100%VE. So a 500 is more than you need

Here is a comparison of some ratios using total TM.
First; the 4.30s and od-box ; 13.29-7.18-4.30-3.14
Next the 3.23s and early box ; 9.98-6.20-4.52-3.23
Next; 3.91s and the 3.09box; 12.08-7.51-5.47-3.91
aaaaand 3.91s with 2.66 box; 10.40-7.51-5.47-3.91
aand one more the 3.09 low; 10.97-6.82-4.97-3.55
As you can see,in the first two; third and fourth are virtually the same, while the od box has a granny low gear, and a 15.8% better second gear.
If fuel mileage matters to you, then I would chose the early A box because you will be hauling with the power going straight through the box in direct fourth. The extra 100 rpm at 66mph shouldn't count for much.
If you need more power to pull at 66mph,then more TM could be the answer.
But if you also need more power at take off,to pull that 9.98 first gear,then I suggest more cylinder pressure.
With the od box you are already maxed out on TM on account of that granny gear.
Whereas with the non-od boxs you still have about 20% left to go . This would get you 3.91s and so; 12.08-7.51-5.47-3.91 with a cruise rpm of 66=3240. (28" tires would drop that to 3060). Passing gear would be 4540@66mph, probably a lotta noise with not much go,using the stock 360
I think the 3.55s would be about the best;10.97-6.82-4.97-3.55; passing gear of 66=4120, a starter of 10.97, and shift speeds of 27,43,59 @3700, then into 4th, or just hold third to 66@4120, then into 4th for 66=2945. 28s would drop that to 2810 With this combo I think I would use a small spread-bore carb with really tiny triple-booster primaries.

Hope that's helpful
 
Last edited:
Not too good; the ratios are too far apart. Unless your 360 was built for torque
What''s the numbers AJ ? A 360 should be able to pull stumps buy like you said about how it's built. A stock 360 should put out around 375 lb/ft at 3000 rpm or so.
 
What''s the numbers AJ ? A 360 should be able to pull stumps buy like you said about how it's built. A stock 360 should put out around 375 lb/ft at 3000 rpm or so.
You must have posted your results while I was typing my post. Dang, you're fast. You can answer questions a few min. before it was asked. :lol:
 
Naw that took me like over 2 hours to bang out in it's final form.

I try to be helpful

Plus I have several years experience with that od box behind a 400ish hp 367. I know it's personality pretty good.
But thanks for the kind words
 
If a person has never driven both the A833 4 speed and its cousin the OD box, they just don't realize the difference in spread between gears.
 
IMO;Not too good; the ratios are too far apart. Unless your 360 was built for torque
The ratios are 3.09-1.67-1.00-.73od. And splits of .54-.60-.73
Lets talk about these splits for a sec. If you take the Rs out to 4000 in each of the first two gears, then the Rs will drop to 2160, and 2400, so your 360 will need some torque down there, to accelerate briskly.
With the 2.66low box having ratios of
2.66-1.92-1.40-1.00, and splits of .72-.73-.71 , the Rs will drop from 4000 to 2880 and 2920. These are fully 33% greater and 21.7%. So just like a hi-stall TC allows your engine to spool up to where there is more power, so also does this 2.66 box allow your engine to remain at a higher power level. So if you already have the 2.66 box, then a straight swap to the od box, while it will launch better, the advantage is lost right at the 1-2 shift. To get any advantage from this box, you need to also change the rear gear.
So lets look at that.
Assuming:
Those tires are 26.7 tall and have a roll-out of ~84", and with 3.23s ,and the od box,and say a torque peak at 3800, and a shift rpm of 4500,
then your speeds at the shifts are 36,66,111,and 152lol. Basically you're asking the engine to pull the load to 66mph with just two gears;then skip direct,and when you drop it into Overdrive the Rs will fall to 1956@66mph. Has your engine got enough torque at that rpm to continue pulling? I venture no. At least not at a small enough throttle opening to be fuel-efficient. So what's the answer?
Well, it might be more gears, so you can use three for acceleration and one for cruising, instead of skipping one.
If you found that your torque monster 360 could get pretty good fuel mileage at 66=2600, then 4.30s would get you that. Shifting at say 4000 now, because you have so much more TM, your shifts would occur at 24,44,74, and 66=3570 in direct, then 2600 in od.Now you are using 2.5 gears to get to 66. With a torque peak still at 3800, you have some passing power and hill-climbing ability in direct. I chose 4.30s because the tooth count is 43/10 and so it is a good strong nearly-impossible-for-you-to-break, ratio... 4.56s would be better but the tooth count is 41/9 and so a bit weaker ratio.

The other option, if that trailer is particularly heavy, or the 360 is weak, would be an early 4 speed; 3.09-1.92-1.40-1.00; and the 3.23s (that you already have). With this "close ratio", now, maybe you can shift at 3800,and your shift speeds would be 30-49-67 and then into direct to cruise at 66=2700. This would be using three gears to pull to 66. Of course passing would be 66=3800 in third gear, bang on the torque peak. The starter gear with this combo is 9.98 so it takes off like a 2.66 box with 3.75s. So it might take a bit of clutch to get moving. 3.55s would be 10% better. I know that doesn't sound like much, but if you had 200ftlbs at 2000rpm then 20 more might allow slipping, from down a couple of hundred rpm. Which means you don't have to rev it up and sound like a Mustang.

With the od box/4.30s,I would run a very small 4bbl. cuz the starter is 13.29, so you will have gobs of take-off power,and the only time you will need a 4bbl is for passing, and you'll be doing about 3200 to 3800,in direct from 60 to 70 mph. Mathematically this requires 417 cfm@100%VE. So a 500 is more than you need

Here is a comparison of some ratios using total TM.
First; the 4.30s and od-box ; 13.29-7.18-4.30-3.14
Next the 3.23s and early box ; 9.98-6.20-4.52-3.23
Next; 3.91s and the 3.09box; 12.08-7.51-5.47-3.91
aaaaand 3.91s with 2.66 box; 10.40-7.51-5.47-3.91
aand one more the 3.09 low; 10.97-6.82-4.97-3.55
As you can see,in the first two; third and fourth are virtually the same, while the od box has a granny low gear, and a 15.8% better second gear.
If fuel mileage matters to you, then I would chose the early A box because you will be hauling with the power going straight through the box in direct fourth. The extra 100 rpm at 66mph shouldn't count for much.
If you need more power to pull at 66mph,then more TM could be the answer.
But if you also need more power at take off,to pull that 9.98 first gear,then I suggest more cylinder pressure.
With the od box you are already maxed out on TM on account of that granny gear.
Whereas with the non-od boxs you still have about 20% left to go . This would get you 3.91s and so; 12.08-7.51-5.47-3.91 with a cruise rpm of 66=3240. (28" tires would drop that to 3060). Passing gear would be 4540@66mph, probably a lotta noise with not much go,using the stock 360
I think the 3.55s would be about the best;10.97-6.82-4.97-3.55; passing gear of 66=4120, a starter of 10.97, and shift speeds of 27,43,59 @3700, then into 4th, or just hold third to 66@4120, then into 4th for 66=2945. 28s would drop that to 2810 With this combo I think I would use a small spread-bore carb with really tiny triple-booster primaries.

Hope that's helpful
Man AJ that's a lot of info, thanks! You should save all this, if you don't already, and have it ready to publish at any time.

So, right now I mostly shift gears at around 3000 rpm unless I'm really getting on it. That means I'm down around 2000 when I get into the next gear and it pulls out of that great. So maybe my 360 is built with some extra torque.

I wish I knew more about all this but I guess I 've got to start somewhere.
 
-
Back
Top