I understand that my car has the unique 10-bolt rear-end. It is original open carrier and gears. I am in the process of gathering components for a major overhaul. One of the items I have already is a 200r4 transmission. I want to go to 3.73 to 4.11 on the ratio, preferably the 4.11. I know TA has the posi carrier (anybody know the actual brand?), but not the gears I want. I found Motive has a gear set, part number BP882411. It has the correct pinion spline count of 27, but the pinion shaft diameter is 1.438". TA says this rear-end uses a 1.875" pinion bearing. So that confuses me because those numbers dont match unless we are talking ID and OD of the bearings... Suggestions or advice?
The only new gear sets for that rear are 3.42 and 3.64. They are made by Fabcraft. No one else makes new gear sets for the 68-70 Buick only 8.2 10 bolt. People mistake it for the 64-67 BOP 8.2 10 bolt. It is not the same rear. https://fabcraftmetalworks.com/product/RAB4-08342/1968-1970-82--Buick-GS-342-Ring--Pinion-Gears/ https://fabcraftmetalworks.com/product/RAB4-08364/1968-1970-82--Buick-GS-364-Ring--Pinion-Gears/ You are SO MUCH better off looking for a 71-72 Buick or Olds 8.5 10 bolt. You can get anything for them and prices are better.
Thanks for the reply Larry. I was hoping I could use my existing... But anyways, I will start looking for alternatives as you mentioned. I guess I might as well ask.... What should I be paying for a complete good rear-end set up with a posi-type carrier and ~4.11 gears. I was quoted by a local guy here for $2,125. That seems at least twice as high as I expected. Car is a 350 cruiser so I dont need anything heavy-duty.....
Not sure, but there are several reputable guys right here on the board that could build you an 8.5 10 bolt rear for your car, and I bet they could beat that price. Screen names Monzaz and BrianTrick. Try PM'ing them and ask.
I can build you a 71-72 8.5" 10-bolt,with Eaton posi or Detroit Tru-Trac,Motive gears(any ratio),and Timken bearings/seals. The housing gets hot-tanked,blasted,primed,and painted. You will get a complete rear,assembled,filled with fluid & additive,and ready to run. I include the brake backing plates. Just reuse your existing brake hardware. Price is $1300.00 plus freight. I can ship Fastenal,store to store,or I can ship ABF Freight,dock to dock. The only thing that you will need to do,when swapping from your 8.2" to the 8.5",is shorten your driveshaft,but if you are installing the 2004R,you will need to shorten it anyway,so you can do that once.
The '68-70 did use a pinion with a bearing diameter of 1.875". This pic is of an NOS GM 3.91:1 R&P I have. As I understand the issue, the Fabcraft gears are designed to fit the 3.23:1 through 3.42:1 carrier flange, which is the carrier TA stocks.
The carrier is a Modified Auburn Posi unit. The reason we made the 3.64 fit the 3 series carrier and not the 4 series carrier is we wanted the gear to fit a LIVE carrier not a 50 year old worn out dead 4 series carrier you can not purchase anymore. Just trying to think down the road to the future. I am pretty sure if you really wanted the 3.64 gear set to fit the 4 series carrier you can have it milled down .100 to .120 thousands and it will fit your 4 series carrier with some shim correcting on the carrier. 3.42 gear is on the 3 series so that does not change. Jim J D Race
