I JUST RE-POSTED MY QUESTION UNDER THE "GOT GEARS?" FORUM..... On my 70 GS 455, the rear axle housing has the number 9799100 cast into it. My research tells me it is a Pontiac rear end. The only letters I found were on the pass. side axle tube on the forward-facing side. The letters are WB. I think it's a 2.56 rear end. Any confirmation on this? Also, can I convert it to posi, assuming it's not a posi in there now? Thanks for any help --gsnewman--
According to my 39th edition Hollander manual, "WB" was used on Pontiac Tempest 2.56:1 non-locking axles from 1965 - 1972. As I understand it, Pontiac used the 8.2" axles through this entire time frame. You should check with monzaz (a board member) to see if it is practical to convert yours to a posi. I would think you would be better off to find a complete 8.5" axle. Parts for the 8.5" are more readily available, and somewhat cheaper. You should post this in "Got Gears?" Jim J.
As a V8buick.com new guy, can you tell me how to switch my question to the "Got Gears?" forum? Thanks-- gsnewman
A moderator can move your entire thread. But, the easier method would be to post a new thread in the gear section. This is a very friendly site. You'll be most welcome on all the sub-forums :TU:
If it is a Pontiac rear, the good news is that new Posi carriers and gears are readily available. Monzaz can give you the best pricing on those parts. Wait until he sees this thread. This is his website. Go to Differential ID, and BOP 8.2 10 bolt, and Pontiac 68-72. http://www.jdrace.com/ I believe this would be the correct Eaton Posi. http://www.summitracing.com/parts/ETN-19674-010/ and Gears. http://www.summitracing.com/parts/RMG-4900821/Application/?prefilter=1
Ok Yes That is a Pontiac housing and there are good amount of parts for that rear. Any and all GM rears can be made posi there is no such thing as a open only rear or posi only rear housing. So The casting you have was in the 70 71 72 era and very common. Pontiac is in my opinion the strongest 10 bolt 8.2 out of all the Buick olds or pontiac and chevy. The bearing caps and casting are very well made and designed. The caps are the thickest and widest in all 10 and even 12 bolt rears. Any way... we have posi units that will fit 2.93 3.08 3.23 ratios we have posi unit for 3.36 3.55 3.90 4.33 4.56 ratios rebuild kits ring and pinions are 3.36 3.55 3.73 3.90 in the aftermarket world I have 2.93 3.08 3.23 good used gears also we can even get you axle shaft for most pontiac rears also. It can definitely be built and will hold well. Jim JD
So Jim, if I've got 2.56 gears in there now, I'd need to swap them out for a different ring and pinion set to put a posi in.....correct? Thanks-- Jonathan H.
Do you want different gears? You choose the posi carrier for the ratio you want to run. Depending on what gear you want, there are 3 different posi carriers. 2.56-2.78 / 2.93-3.23 / 3.36-4.33 and up
2.56 and 2.78 posi unit will be a bit difficult to find as it will need to be STOCK unit. There are NO aftermarket 2 series units made on the market. Jim I think we sold our last one a few months ago. They are / were selling pretty good there for a while when gas was way up in price. Jim JD
So, if I'm not taking my car to the race track, but want posi for those times that I want to accelerate quickly beyond the posted speed limit.....what would you recommend I do? Do you have a gear set that I could buy from you and have you install, as well as a posi to match? And would you recommend Eaton over Auburn? --Jonathan
A Posi isn't going to accelerate the car any quicker unless you are spinning the tires. You'll just spin both tires instead of one. Gears multiply torque, and given enough traction, will accelerate you quicker. Higher numerical gear sets will give you better performance, but will also increase engine RPM at all speeds, and gas mileage will be less. A 3.08 is a great compromise between performance and gas mileage. All you need to do is buy the posi carrier, and gears. Monzaz can sell you what you need.
Eaton or Auburn no matter here. People do have preferences But if they are all taken care of and not overly abused they all will do the job for year sand years of good burn out action. I always suggest NEW if you can afford it OR if it is even available for the rear diff your building. Larry is right about the acceleration part. Having 2 wheels pull is better and will usually delivery more of the power evenly to the ground but the 2.56 open and 2.56 posi both with good traction will accelerate identically in rate of time and speed. We have 2.93 3.08 gears which you will notice a quicker acceleration from the 2.56 and will still keep your muscle car on the freeway with plenty of top end to spare. Jim
