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Username Post: new gears        (Topic#347998)
Posts: 907

Loc: lexington ky
Reg: 06-03-12
11-01-17 09:12 AM - Post#2712932    

i need to replace my ring and pinion gears , is this ok to use BELAIR-I...

1958 Chevy Biscayne
235 6 cyl
2 speed P/G tranny

1953 f100
350 chevy
350 turbo

1955 chevy 210
LS motor (soon)
4l60e (soon)


Honored Member
Posts: 27574
Loc: San Francisco, CA
Reg: 11-26-02
11-01-17 11:31 AM - Post#2712946    
    In response to lilrobo

The ebay listing says, "will not fit some 1955-1956 models with 306 casting number", so check the casting number on your center section.


Those who choose an automatic transmission want transportation. Those who choose a manual transmission want to drive.

Valued Contributor
Posts: 4781

Age: 67
Loc: Addison, IL
Reg: 05-28-10
11-02-17 08:18 AM - Post#2713046    
    In response to raycow

Some of the early cases used a thick or thin version of the ring gear. I forget which it is. Your chunk could be from a different year so check that out also before you buy.

Honored Member
Posts: 27387
Loc: Katy, Tx, USA
Reg: 07-06-00
11-08-17 05:42 PM - Post#2713701    
    In response to models916

The main 3rd member housing itself is not the question, though an early housing would indicate what parts were used in the assembly.

What does count is the differential assembly. 55-56 3rd members were only available in 3.55, 3.70, and 4.11 ratios. They do not accommodate 3.36 or 3.08 ratios which have a bigger pinion gear. So the ring gear mounting surface of the differential housing is closer to the center than on the later differential housings, and the thickness of the ring gear is different too. You can't mix the gear sets and differential housings without custom parts and machining - and there's no need to do that.

Just use 55-56 gears with 55-56 differential housings, and 57-64 gears with 57-64 differential housings.

The third member housing does not need to be changed with one exception. If you use a posi unit, you have to remove a gusset on the third member housing that's in the way. This goes for any third member housing not originally used for posi, whether it's 55-56 or 57-64.

Since posi was only available on 57-up, you have to use 57-64 gears with it.

Also, any complete 55-64 3rd member can be used in any 55-64 axle housing.

Valued Contributor
Posts: 4781

Age: 67
Loc: Addison, IL
Reg: 05-28-10
11-09-17 05:47 AM - Post#2713740    
    In response to Rick_L

No gusset to remove inside the 56 for adding a posi from what I remember. Maybe 55 also. It was added later because of issues with the strength of the originals. wouldn't use a posi in a 56 drop out. Get something newer. JMO


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