I have a 1969 deville that i'm looking to swap the differential in. But before i get into it i'd like to know if it was a proprietary differential or if there are other gm diffs that will fit the carrier rearend. Any help is greatly appreciated as it could save me a bunch of time and money.


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not enough info ..

All soup aint soup.

there are 10 bolt, 12 bolt, maybe more ...
there are posi-traction, standard, and locking ...
there are 3:55, 3:73, 4:10, and maybe more ratios ...


then again, if you swap with one of same bolt pattern, ignoring gear ratios or type, it probably will physically fit.




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thanks for the reply and sorry for not providing enough info. Rearends arent my area of expertise which is why i'm having this issue. I'm not sure what the factory rear or differential is in any way shape or form, i do know that i need a limited slip, or better yet a locker in for my current setup. But i have no idea if i'll be able to find one that will bolt in or if i am going to have to change the whole rearend. As for gear ratio, the stock ratio is 2.93 and my transmission guy and i will be able to work with that if need be. I dont want to get too crazy with the gears since its a street/highway setup without overdrive. My main concern is traction right now....no one legged burnouts.

I know i dont have much to go on for info, but i hope someone can tell me what i need to know. Thanks again.

 

Its been a long time since I pulled out spiders and pinions, set backlash, etc .. but ...

Many cars even being very close in model year use different internals, even though the cover on the differential has the same number of bolts.

Identify what you have first. You need a few tools to do the swap correctly:
- Impact gun,
- Dial indicator, to set gear backlash
- torque wrench
- Pinion depth gauge

the critical things to measure are the pinion depth, pinion bearing preload, carrier side clearance, and gear backlash. These are all outlined in the shop manual - you do have one, right?

To upgrade an open differential to a posi, you must change the carrier to a posi type. That is, just the "guts" inside the rear end, keeping your existing gear set.

An entire rear end from another GM product is a bolt-in fit as long as you're doing it in the same body style. Minor differences such as brake lines and U-joints are the only minor trouble spots. Cadillac, Buick, Olds, and Pontiac rear ends are interchangeable if they are the same frame size.

1964 to 1967 A-body 10 bolt rear axles, with 1968 to 1972 A-body axles, the entire housings will swap.

1964 to 1967 axle is ¼" narrower. But at 1/8" per side means, for all intent and purposes, they are the same.

As a general rule, most of the axle shafts will swap as long as they have the same spline count, excluding 10 bolt "C" axle shafts (Chev) which have an internal "C" clip to retain the axle in the housing and use a roller bearing in the tube end.

The rest have a bearing pressed onto the axle and then bolted to the tube end.

Most GM diffs carriers carry ring and pinion sets up to 3:42. After that (3:73 and up) you have to change the carrier. As the pinion gets smaller with the lower gear ratio, the deeper the crown gear gets. Instead of making extremely thick crown gears, GM made two types of carriers instead.

As for gear combo, say if you had just a posi carrier with say a 2.73 gear, you could put a 4:10 gear or even 4:33 with compatible gears, shim it because when you put higher gears on the carrier, the carrier shifts. These shims go between the carrier bearings and the start of the axle tubes in the housing.

OR, do what I did the last time I swapped .. I bought the whole darn axle with the gear set I wanted, opened it, drained it, washed it with solvent, new seals went on, then I unbolted mine from the car, bolted the replacement axle set, installed new brakes, lines, filled the rear end with 90W, etc .. and off I went. Tools needed for this method? a set of box ends, sockets, chisel, hammer, pliers.

Maybe the time for me to sell my PROTO box filled with a variety of specialty tools is coming.

Like I said, its been a long time since I messed with spider gears and pinions and that was cuz them spider gears broke on me -a Mopar unit.

Now that I said ALL THAT .. may I ask why are you doing it?




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Wow..thats alot of info, thanks, i do appreciate it and you can bet i'll take it all into account when i'm planning this project. I was hoping that there might be a simple answer that someone could direct me toward as opposed to having to take things apart first. So i thought i'd post here and see what was out there since i'd like to keep the original rearend and just change internals if at all possible. I'm still open to the option of an entire rearend swap if need be, but like i said i'd like to keep the original housing.

The reason i'm doing it is because i just dropped in one of potters performance 500's and i'd like to maybe play with the gears a bit, but i definately want both rear wheels to lock up when i stomp on it so i'm thinking locker. Traction is definately my main objective right now since my tranny guy says he can work with the 2.93 gears i have now so that i dont lose my highway drivability completely. But i'm planning on redoing the entire driveline and want to get all the facts and figures so i can plan accordingly since each part depends on the other parts in the sequence.

 

I thought I did .. so let me try again. You seem to be highly concerned on cost, and to avoid unnecessary expenses one needs to do homework and I gave you that route.

but, getting back, the year was 1969 .. 50 years ago .. your car has what in it?
you dont know .. for all you know, the rear end has been changed or retro or mod or fixed or ????

also, that is about 4 years before big government jumped in and started telling the auto industry what to do with the drive trains so .. there were not many rules, or at least, not many when it came to the drive train. In those times, people that knew next to nothing about cars, would pick up parts at their local yard and drag them home, made them fit.

And THAT is my simpler answer .. hit the pages of Craigs or search the huge yards of vintage cars in the deserts (Arizona, Nevada, New Mexico, etc...) for vintage rear ends of that era of similar body size of your car .. open it up, inspect the teeth, calculate the gear ratio of the, drag it home. If you should make a mistake, do***ent what you got, rations/condition/car body, put it on Craigs for the next guy doing a project.

Its a project, right? In a project, anything (almost) is a possible solution.

ohhh .. if you take out the gears (except for the spider set) out, do learn to set a backlash upon the re-install.. it is easy, but it is also important.

One last thing .. the two "weak" parts are the axles (shafts get twisted ) and spider gears (get crushed). Inspect that carefully.

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