Differential Positraction

I want to convert my 1968 Buick Wildcat Custom 2 Door OEM single wheel (open differential), differential to a GM 1968 OEM Positraction and use my original GM 1968 OEM gears. I need to know what to ask for when contacting junk yards, used-parts dealers, etc., for a used GM 1968 OEM positraction. Example, did the full-size GM 1968 Buick Wildcat positraction differentials come in OEM series, (which used specific gears) like the full-size General Motors 1957-1964 Pontiac/Oldsmobile positractions?

I was old some years that the GM 1968 Buick Wildcat Positraction is the same as the GM 1968 Electra Positraction. Are there other GM models and what GM years that would fit with my GM 1968 OEM gears? What are the identifying numbers, letters, symbols, features, methods to identify the used applicable GM OEM Positraction for 1968 that would fit my 1968 OEM gears?

What is the information source and other contact methods, ex. names and/or phone numbers. What are some possible sources for used applicable GM OEM 1968 Positractions or other models and years that would fit my 1968 GM OEM gears.

 

B C or E body Buicks 67-70 9 3/8" only. No LeSabres except for the 70 LeSabre 455.The carrier will also have to be compatible with your numerical gear set.

 

The 1968 Wildcat is a B body with a 430 cubic inch engine. How do I determine what carrier I need and how do I determine what numerical gear set I have now?

 

Take off the rear cover and the numbers for the ring gear are inscribed on the ring gear itself. They will read something like 40-- 13. To get the ratio divide 40/13 = 3.07. The standard ratio offered for your car was 3.07, but this does not mean it could not have another ratio.

Carriers can handle a series of gear ratios within a given range. It may be say 2.56 to 3.08 but nothing higher. It would take a different carrier for 3.23, 3.42 etc. in other words, one carrier does not handle the entire spectrum of potential gear ratios.

I would buy and use a carrier with the gears included. Trying to set up a used set of gears with a pattern already imprinted is risky for noise.

 

A Wildcat could have come from the factory with 3.42 gears. One carrier is for 3.23, 3.07, etc. The other carrier is for 3.42 ratio & up & are the harder, much more expensive carrier.

 

BUYing a gears set already on the posi NEVER guarantees a good set-up ANYTIME a ring and pinion are swapped into another husing you will need to double check the pinion depth again. NO 2 housings are ever the same. Sorry... That info gets TONS of guys into trouble as they think they can just bolt in ring and pinion assuming it was all together in another housing it will just bolt right up in mine no problem ...NOT TRUE....

just finding gears and a posi for this rear will be tough enough.

Jim
J D

 

Carrier break for the BUICK 9.3 10 bolt cover rear 12 bolt ring 1966-1970 era
2.56-2.73 1
2.93- 3.08 2
3.23 -3.42 3

REMEMBER 1966 posi carrier will be ALL ON ITS OWN it has the same size bearings driver side and passenger side.

So 67-70 is all you can use and BUICK ONLY CARS
Electra, Wildcat, Riveira etc.

I actually still might have a Posi unit all reconditioned on the shelf still....

 

I have a 1970 Buick Electra which had an open differential with 2:56 gears and, swapped the entire rear end for a 1969 Wildcat which had 3:07 gears and a posi. I later put in 3:23 gears with a posi, and used the same carrier from the 69 Wildcat.. I don't know the carrier breaks, but my 3:23 gears and posi which came from a 1970 LeSabre donor car with a 455 fit in the same carrier as the 69 Wildcat rear end which came with the 3:07 gears and posi. I recently found a set of 3:42's with a posi from a 68 Riviera GS. Don"t know if they fit but will have my mechanic give it a try in a few months... I know the entire rear end on a Riviera if different from the Electra's, Lesabre'455 and Wildcats, but I was told the interenals are the same.

 

Pretty sure 3.42 is the break from 3.23 --- you could make a spacer to do the job also it will move the ring over to engage the pinion and keep the carrier centered in the case. You will need longer bolts also to prevent bolt failure also. Jim