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Discussion Starter · #1 ·
i read in a article once that they took whatever transmission behind a hemi cuda they took it and changed the gear ratios and kept it a 4 speed but 4th was overdrive


can we do that with any other transmissions and who was the company that did that if it did happen?
 

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you're kinda close to the mark.
ANY 4 speed with 4th being DIRECT DRIVE (ie 1:1) has the possibility of having this done.
Warner had a pre-production OD 4speed; Auto Gear made an M21 OD (no longer in production) for the Muncie, and New Process took the 833 and made the 833OD which is similar to the 'hemi' box but built for pick up trucks. Passon Performance is the place for these. Also; a NP 833 OD has a Hurst shifter from the factory. And; the 833OD was used in DODGE and GM pick up trucks.

Heres how its done:
The trans needs 1 gear to be Direct Drive that will become your 3rd gear
The actual OverDrive gear on the mainshaft is in the 3rd Gear position
This requires you to have a 2nd gear with the right ratio to bridge the 'gap' from 1st to direct drive (now 3rd). What youve done is essentially create a 3 speed with an overdrive 4th.
You flip your shift lever for 3/4 upside down and it will shift 1-2-4-3 in the trans and your standard H-pattern in the cab. Sneaky huh? We're good.

I dont have the NP833OD ratios handy; but heres what WE did several years ago for the M21OD (this is NO LONGER in production). 2.20 1st, 1.50 2nd, 1.00 3rd and 0.86 4th.

Now here's why WE don't produce it anymore:
Due to the constraints of the physical dimensions of the Muncie main case; you cant fit a 2.5x 1st gear in the case with the overdrive gear; so we're stuck with a mild OD for a 3.70-4.00+ rear gear. Due to the noise generated by running an oversize gear inside the main case, we had to run it on the tighter helix M20/21 platform. Your average gearhead can trip over a 400hp SB which is gonna stress this gearbox (even with the supercase and iron midplate) because you have really wide gear splits, a heavy gear in 3rd gear position, and the lighter duty M21 platform. Did I mention that gear is oversize? Its a royal pain in the butt to assemble it; you basically sneak the 3/4 slider over as far as you can and try to weasel the geartrain in and then you bump it and the struts and/or springs drop out. Also; because you require a special gear for 2nd speed, an oversized gear for the 3rd gear position and a new cluster gear...it requires new hobs (cutting equipment to make the gear), custom gears in a short run scenario (say 100 pieces) AND very finnicky attention to detail in making the OverDrive in order to minimize noise and vibration. My boss George bit the bullet and bought 200 complete sets from Antonio Masiero in Italy after doing all the design work himself.
Its a hard sell "you get a lighter duty (sub 400ft pounds manufacturers recommendation in most cases) 3speed with overdrive Muncie that doesn't have enough 1st gear to use with anything lower than a 3.55 in a light car" and when our complete M22Wide's were $2000; this was $2150 I believe. I never had one complaint from a customer; but the cost of doing this at Chrysler (New Process) or Warner in thousands of units, versus 1 guy on his drafting board for say 200 units every 5 years...LOL

Warner and NP did this during the first gas crunch back in the 70s as a quick fix to get people overdrive and sell V8 cars without tooling up for a 'modern' 5 speed. The first Borg Warner car 5speed was the T50 and it was used in things like the Vega. It was all torrington style bearings and had some really interesting design excercises (its endloaded like a T56 and was diecast). Doug Nash mingled T10 and Turbo Hydramatic parts and came up with the 4+3 in the Vette. It worked great but wasnt really designed for the Vette, it had something to do with GNs Camaros etc and the General insisted it go into the vette; several people had different ideas of how it needed to perform and Corporate politics really took the wind out of Doug's sails. BW also designed the T5 which is nothing T50 at all other than 5 speeds and from BW. The T5 is an outgrowth of the T4 4speed.

So there you have it; yes it can be done; pony up about 50grand and its easy LOL. It works and works well if you use quality parts, it'll be a flaming pile if you use Chi-com, Indian or Korean parts. Its very niche market and needs high volume to be feasible, and then you need to deal with the half-ton pick up truck ratios. Fine for cruisers, bad for performance enthusiasts.
Youre better off going with a 2.88 1st T10, or 2.98 (custom) Muncie 1st gear and a highway axle ratio like a 3.08. This gets you a traditional 4speed (no surgery required), a lightweight package (ours is 85 pounds) and a traditional price structure. Sorry for the long post
 

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New Process built an OD 4 Speed for GM from 81 to 87. It came in their light duty trucks (C-10 and Vans). The first year was an all aluminum unit with a GM bell housing bolt pattern and all the dimensions were identical to the Muncie, Saginaw and Borg Tranys. (Input Shaft (10 Spline), Output Shaft (27 Spline and Trany Mount Location). After the first year they went to a cast iron unit with a Chrysler bolt pattern and modified their bell housing bolt pattern to accept the Chrysler pattern. The unit is an NP-833, or NP440. Ratios are very similar to the 700R4 (3.09, 1.67, 1.00 and .73 OD). Its an OK trany for street driving and cruising, but not for racing as you can see in the 1st/2nd delta (Wide). I have one of the aluminum units and would consider using it in my Hot Rod for cruising with a 2.73 to 3.08 rear ratio. Right now, I have a Muncie in there and no urge to change it out. If you do a search on this forum using a-833 you will find a lot of strings addressing this trany.

If you are looking to modify a Chrysler unit, look up Alan Passon Performance.
 

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i read in a article once that they took whatever transmission behind a hemi cuda they took it and changed the gear ratios and kept it a 4 speed but 4th was overdrive
The transmission you are thinking of is the A833. In reality, THIRD gear was changed to the O.D. gear, fourth remained 1:1. Chrysler simply flipped the lever on the 3-4 shift arm so that the "H" pattern went 1-2-4-3, providing the driver with three standard gears and a "fourth" that was O.D. More info is in this link - scroll about 2/3 of the way down the page.

Chrysler A-833 four speed manual transmissions ? history, tech, and swap
 

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New Process built an OD 4 Speed for GM from 81 to 87. It came in their light duty trucks (C-10 and Vans). The first year was an all aluminum unit with a GM bell housing bolt pattern and all the dimensions were identical to the Muncie, Saginaw and Borg Tranys. (Input Shaft (10 Spline), Output Shaft (27 Spline and Trany Mount Location). After the first year they went to a cast iron unit with a Chrysler bolt pattern and modified their bell housing bolt pattern to accept the Chrysler pattern. The unit is an NP-833, or NP440. Ratios are very similar to the 700R4 (3.09, 1.67, 1.00 and .73 OD). Its an OK trany for street driving and cruising, but not for racing as you can see in the 1st/2nd delta (Wide). I have one of the aluminum units and would consider using it in my Hot Rod for cruising with a 2.73 to 3.08 rear ratio. Right now, I have a Muncie in there and no urge to change it out. If you do a search on this forum using a-833 you will find a lot of strings addressing this trany.

If you are looking to modify a Chrysler unit, look up Alan Passon Performance.

Jamie Passon I do believe; in Pennsylvania
 

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Discussion Starter · #6 ·
wow i didnt think it was hard it seems on paper just make 4th a od but wow i dont think it worth that much to make a 4 speed toploader into a od.



what is the best overdrive manual u can stick in a 71 mustang behind a built up 460
 

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High Performance Rear Ends
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I've got a 4 speed toploader Ford that is an overdrive transmission. Ford made them in '77 and '78 I believe and used them in the Granada and Mercury. This one has a bulge in the case for the larger overdrive gear in the 3rd gear position.
 

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I've got a 4 speed toploader Ford that is an overdrive transmission. Ford made them in '77 and '78 I believe and used them in the Granada and Mercury. This one has a bulge in the case for the larger overdrive gear in the 3rd gear position.
It was also used in pick up trucks I do believe; but Im missing my factory lit. for late 70s Ford at the moment
 

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Mustang RUG ?

Wasn't the 82 mustang 5.0 Ho Trans a top loader 4 spd Od trans The Case looks the same as the old ford top loader 4 speeds but has the top aluminum cover with the single rail shifter ? I sold my 82 Mustang in the ealy 90's
 

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I built several Jerico transmissions for a Busch Grand National team about 15 years ago with overdrive in 3rd for one of the road race tracks. I can't remember which track it was, and I never figured out why the used an overdrive gear instead of changing the rear end ratio. I learned a lesson about drive shaft speed, vibrations and diameter at the same time.
 

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I dont understand the desire for OD in road racing; often times you get weird splits and shift quality and longevity suffers. I just had a customer in road racing take his TKO out and put our 4 speed in the car, keeping the same rear gear. His preliminary reports are a track record for his class, and more concise control of the engines powerband. I suppose if you had really long straights and were required to run a 4.11; it makes sense as a crutch for the once or twice a season; but Id rather have them drop the rear gear and run a tighter ratio spread. Less heat build up, faster shifting.
 
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