My imp
Well-Known Member
Does anyone know of an affordable Mopar OD trans for a big block? The gear vendors kit is over $3000! Just for the OD unit, you don't even get the drive shaft! No discount if you bring your own wig & lipstick either!
Mopar OD trans for Big Blocki
- Thread starter My imp
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slant6billy
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A parts boneyard (not a junkyard) I used to go to for F parts had a few Winnebago motorhomes. Late 70s/ 80s models with bigblock mopars. One had a gear vendor's unit on a 727. Roadrunninmark found them on some others too. I've have heard that this was a common find if it was a mopar drivetrain in those Winnebagos, but perhaps someone could confirm that. If it is true, what is the cost of a 30 yearold beat Winnebago.
MiradaMegacab
Well-Known Member
SMR transmission has an adapter plate for a 518 to a BB Mopar.
Or JW transmission has the Ultra Bell, you cut off the stock bellhousing and bolt on the new one.
Or JW transmission has the Ultra Bell, you cut off the stock bellhousing and bolt on the new one.
833 O/D?
Made from 76 up into the late 80's at least.
Somewhat common behind a slant six in trucks, but can be made to work with new bell housing, which is either easy to find and pricy, or moderately difficult to find and a lot cheaper.
Made from 76 up into the late 80's at least.
Somewhat common behind a slant six in trucks, but can be made to work with new bell housing, which is either easy to find and pricy, or moderately difficult to find and a lot cheaper.
My imp
Well-Known Member
Thanks for the info. The ultra bell is more affordable, & quite frankly, adapter plates only offer 1/4" thread depth. I'm not to comfortable with that.even with factory bracing, I don't know how strong that would be?
My imp
Well-Known Member
$100. When I retired in 2002, I could've had one for $100. 440/727 with 9000 (yes 9000) miles on it. Had no where to put it to strip it, no one would let me take to their place & let me strip it, plus I retired on disability & COULDN'T strip it. Could've had a Chevy w/427/TH400 for $300 with the same miles! But that was a Gertenslager (10 times uglier than a Winnebago) mobile classrooms that Parma Schools no longer used.
greymouser7
Well-Known Member
In 1976 V8 (318/maybe canadian 360) stick F and A bodies came with A833 cast iron overdrives-have been told that they are much more stout than the 225/318 1977+ aluminum overdrive four speeds - both are .73 which is better than gear venders- for under $2000 Jaime Passon sells conversions to change cast iron four speeds to stout overdrive pieces...
Well, sorta yes and sorta no...
The cast iron A833OD was introduced in '75 on the A-bodies and I may be wrong but I believe it was Slant Six only. The aluminum case came online for the Dart Lite & Feather Duster, both of which were economy-minded /6 models built in '76 (and make great drag cars). The OD was never installed behind a 360, anywhere (no examples have surfaced to date). About mid-year the cast iron piece was phased down and by '77 was gone from production.
"Much more stout" is an overstatement in regards to the strength difference between the cast iron and aluminum cases. The aluminum cases are plenty strong themselves and lots of racers used to use those instead of the MP aluminum case to lighten their cars. The strength issue with the OD is the floating countershaft, which was incorporated to help suppress gear rattle. For lack of better terminology the countershaft flops around in its bores, particularly at the front, which is not the case with any of the close-ratio transmissions (none of which were available in F-bodies). The "muscle" transmission's countershaft was a press-fit in the case. What happens is that under hard acceleration, quick transitions from coast, or hard clutch usage, the countershaft beats the hell out of the case. While it is true that the iron is less likely to deform than the aluminum, it's still a problem. Anyone who's ever taken out a cone-type diff with an ovalled pin bore knows can tell you that Chrysler did not use premium iron in situations where constant direct wear were not an issue. In other words, they didn't use the same iron in the transmission cases that they did in the engine blocks. It wasn't considered necessary when the transmission was designed with the fixed countershaft. When they changed to the floating design, it was not deemed "over-engineered" enough to last behind even the 360-2V and later the 318-4V.
The only difference between the iron OD and the aluminum one is the case material. Everything else is identical, right down to the metallurgy of the gears. The iron case is considered desirable because the countershaft is less likely to deflect, but it's not some magic cure-all. Were an aluminum case to be welded & re-bored so the countershaft was fixed, it would be stronger than the iron case. There is a cure for this, which I plan to have done to the transmission I'll be using in the Imperial. Click here for details. The article actually makes it look harder than it really is. Read through it a couple of times.
The Passon gearset has absolutely no basis in the original A833OD other than the fact that it uses 3rd gear for the overdrive position. All the gears are new, custom-made pieces using the fixed countershaft design and correcting the other problem true of the original: the miserable gear spacing. First gear is too low to be really useful with a deep gear like a 3.91, which would be otherwise great with that .73:1 overdrive. By design, nothing can be done about "third" gear, since it's actually fourth gear, meaning direct drive (this is the case with Passon's setup too). 3.09, 1.68, 1.00 and .73 does not an ideal transmission make. You need a wide, flat torque curve to not be concerned with the huge drop between gears, particularly 1st to 2nd. 360? Stroker? Not a problem, but if you've got a .550" lift camshaft in a 318 it's probably not going to be an optimum transmission choice.
Strangely enough, that wacky wide gear spacing is about perfect for a turbocharged application... but even then, I'd rather it had a first gear in the mid/high 2:1 range.
At one point I had calculated out the optimum gear for most applications using an A833OD to be a 3.36. It's a tough gear to find, being only used in the 8.75" and only in '60-'61. Barring that ultra-rare find, for most naturally-aspirated engines will be happiest with a 3.21 or 3.23.
The cast iron A833OD was introduced in '75 on the A-bodies and I may be wrong but I believe it was Slant Six only. The aluminum case came online for the Dart Lite & Feather Duster, both of which were economy-minded /6 models built in '76 (and make great drag cars). The OD was never installed behind a 360, anywhere (no examples have surfaced to date). About mid-year the cast iron piece was phased down and by '77 was gone from production.
"Much more stout" is an overstatement in regards to the strength difference between the cast iron and aluminum cases. The aluminum cases are plenty strong themselves and lots of racers used to use those instead of the MP aluminum case to lighten their cars. The strength issue with the OD is the floating countershaft, which was incorporated to help suppress gear rattle. For lack of better terminology the countershaft flops around in its bores, particularly at the front, which is not the case with any of the close-ratio transmissions (none of which were available in F-bodies). The "muscle" transmission's countershaft was a press-fit in the case. What happens is that under hard acceleration, quick transitions from coast, or hard clutch usage, the countershaft beats the hell out of the case. While it is true that the iron is less likely to deform than the aluminum, it's still a problem. Anyone who's ever taken out a cone-type diff with an ovalled pin bore knows can tell you that Chrysler did not use premium iron in situations where constant direct wear were not an issue. In other words, they didn't use the same iron in the transmission cases that they did in the engine blocks. It wasn't considered necessary when the transmission was designed with the fixed countershaft. When they changed to the floating design, it was not deemed "over-engineered" enough to last behind even the 360-2V and later the 318-4V.
The only difference between the iron OD and the aluminum one is the case material. Everything else is identical, right down to the metallurgy of the gears. The iron case is considered desirable because the countershaft is less likely to deflect, but it's not some magic cure-all. Were an aluminum case to be welded & re-bored so the countershaft was fixed, it would be stronger than the iron case. There is a cure for this, which I plan to have done to the transmission I'll be using in the Imperial. Click here for details. The article actually makes it look harder than it really is. Read through it a couple of times.
The Passon gearset has absolutely no basis in the original A833OD other than the fact that it uses 3rd gear for the overdrive position. All the gears are new, custom-made pieces using the fixed countershaft design and correcting the other problem true of the original: the miserable gear spacing. First gear is too low to be really useful with a deep gear like a 3.91, which would be otherwise great with that .73:1 overdrive. By design, nothing can be done about "third" gear, since it's actually fourth gear, meaning direct drive (this is the case with Passon's setup too). 3.09, 1.68, 1.00 and .73 does not an ideal transmission make. You need a wide, flat torque curve to not be concerned with the huge drop between gears, particularly 1st to 2nd. 360? Stroker? Not a problem, but if you've got a .550" lift camshaft in a 318 it's probably not going to be an optimum transmission choice.
Strangely enough, that wacky wide gear spacing is about perfect for a turbocharged application... but even then, I'd rather it had a first gear in the mid/high 2:1 range.
At one point I had calculated out the optimum gear for most applications using an A833OD to be a 3.36. It's a tough gear to find, being only used in the 8.75" and only in '60-'61. Barring that ultra-rare find, for most naturally-aspirated engines will be happiest with a 3.21 or 3.23.
