Need New Rear End Gear Ratio

[Guest]

Its quite possible that i may have to replace my rear end gear set.three nights ago,i heard a loud grinding sound and the car started jerking a bit and i drove slower so as not to sieze up.Hopefully its just the bearings in te rear,but if its not,who makes 2.56 ratios for gm 10 bolt bootys.

[Guest John Chapman]

Capt E...

You sure it's not a universal joint gone bad?

JMC

[NTX5467]

I concur with John, that it might be something other than the ring gear/pinion set. Better get it to a shop and torn down before anyone starts jumping to conclusions or makes speculations. Might even be a parking brake mechanism that has self-destructed in one of the rear brakes. Could be a one of the pinion or side gears inside the differential case has a problem.

If it's the normal Chevy 10 bolt rear axle, the part number in the GM Parts database will probably be discontinued, but there is a listing for a 2.56 ratio in the GMPerformance Parts catalog that still works. Some of that stuff is also available aftermarket through places like www.ringpinion.com (Randy's Ring & Pinion), but you should be able to get the stuff locally too.

When I recently had the rear axle on my '77 Camaro rebuilt (due to noise concerns), this time it took two new axle shafts (one previously replaced with the bearing and seal about 3 yrs ago with a good, used shaft) and all of the bearings. The gear set was still in good shape after over 550,000 miles so I somewhat doubt you would need a ring & pinion gear set due to wear concerns.

Getting an axle out of the salvage yard will not be "cheap" either, plus you could be getting something not that much better than what you have PLUS have to swap your (perhaps in better shape) stuff onto the replacement rear axle assy.

All things considered, don't try to patch it up just to get by, do it right so you won't have to worry about it again.

Enjoy!

NTX5467

[NTX5467]

Be fully aware that there are two DIFFERENT sized ring gear rear axles that have 10 bolts holding the rear cover on. When people usually refer to "10 bolt" GM rear axles, they normally are referring to the common Chevy 10 bolt with the 8.5" diameter ring gear. The rear cover for that axle is completely round.

GM also has another "10 bolt" rear axle that went in a multitude of B/C cars in the later '70s to middle '80s, plus S-10 light trucks, Camaros/Firebirds, and earlier '70 lower powered 6 cylinder Chevy Nova-type cars. The rear cover on that axle is more squared than rounded. This is the 7.5" diameter ring gear rear axle.

Very few if any parts interchange between them too. In the earlier '70s and prior, there were also "BOP" axles with unique Pontiac and Olds rear axles in the mix. Visible differences in the rear covers of these axles too.

2.56 gear ratios typically were replaced by 2.41 gear ratios after about '79 or so.

It's one of those deals where you have to know what you have instead of just guessing.

Enjoy!

NTX5467

[Guest]

Your rearend is a 9 3/8 size 10 bolt cover .It is only style that came under the Electra. It is the same as the Wildcat and Lesabre 455.

The internals from any 69-70 Riviera,Wildcat,Estate wagon and Electra will work for your application. Common ratios 256 278 308. Harder to find 342. Pain in the butt 391 478.

A complete rearend ,drum to drum, from a 1969 or 1970 Lesabre will bolt in also. These use the same gearing as the 70 GS 8.2 rear giving options such as 323,364 if you prefer.

[Philippe Racicot]

I think most late sixties to mid seventies Wildcats, Le Sabres with 455, Electras and Rivieras had 8 7/8" Pontiac built rear end while Le Sabres had a 8.5" Buick rear end. They all have 10 bolt covers. I recently ordered a set of bearings for my 75 Electra from my local Napa store and they were quite confused with "10 bolt" rear ends. They ordered 3 Kits that were all different from mine and I finally had to order bearings separatly with what remained of the numbers on my old bearings...

[baking]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> Some of that stuff is also available aftermarket through places like www.ringpinion.com (Randy's Ring & Pinion), </div></div> I had VERY bad luck with Randy's Ring & Pinion and would stay away from them.

I upgraded my 10 bolt '70 Skylark to an aftermarket posi. I still have the old differential with the ring and pinion. Probably won't fit your car, but it's free for shipping costs if you or anyone else wants it.

[NTX5467]

I mentioned that particular business as I could find the address easily (it's in most every car magazine that deals with high performance stuff), but I also know there are other similar sites. That company seems to have been one of the first to jump off into that sort of aftermarket sales of rear axle parts. Not an endorsement by any means, just a mention as an example of what might be on the web.

When dealing with the earlier GM rear axles, they certainly aren't the same even though they perform the same function. Each GM division typically had their own designs although some of the higher car line axles could be used by other divisions too. Number of bolts holding the rear cover doesn't mean nearly as much as the shape and size of the rear cover housing (i.e, "cut-out" cover, completely round, somewhat squared-off round).

Ordering parts by application could be the best orientation instead of trying to describe the rear axle to some guy behind the counter that's younger than your car or has little experience in such matters. Hopefully, there might be an illustration section when dealing with the rear axle gasket in the aftermarket rear axle parts catalogs so you could use that for definitive identification.

As mentioned, many of these rear axle service parts are available locally from NAPA and such. Always better to deal with someone local when you can if you don't really know what you're dealing with on the vehicle. The more popular (i.e., high volume) applications might have kits available, but the same parts for other vehicles would be available as individual items.

Also, when in doubt, consult the applicable GM Buick Service Manual for correct identification of the rear axle.

Enjoy!

NTX5467

[Guest]

Sometimes it is very hard to find someone who knows what rear parts fit the Buicks. Some Riviera guys have had good luck with Ratech Mfg who seemed to know what fit and had the parts needed. I haven't used them myself but it's worth a shot if you have no luck locally.