Hello, I have a 10 bolt 8.5 out of a 71 gs. All redone and went through with new brakes,etc,complete. Has the factory 3.08 gears. Switching to a 12 bolt and wondering what the 10 bolt would be worth to sell? Thanks
Posi?:Brow: Im interested $300 and up ..1 leg ?:moonu: .11 cents a lb scrap value.I got 3 or 4... come and get em If you want.
Worth- That is all on whether someone needs that ratio for a restored car. core open sell for 100-200 here- most are pretty rusty here. Posi 250-500 at a 3.08 ratio 3.42 posi original coded rear could be double easy. considering there are a lot still out there in yards and under cars and parts are readily available... not as much as you would think. Most people are using the 8.5 for its strength and most will want a upgraded posi, gears and axles in these (BUICK 12 bolt chevy rears) Factory bolt in axles. Just some thoughts and info . Jim J D
Oh, Wise guy ehhh. Here's why. The 1971-72 8.5 10 bolt has: 1) The same pinion shaft diameter as a 12 bolt 2) Same Pinion support as a 12 bolt 3) Can be upgraded to 30 spline Moser axles (as I did, which equals the 12 bolt) 4) Bolt in axles (no stinkin C clips, no need for C clip eliminators, and possible leaks) 5) No need for the hybrid U -joint with smaller cups on one axis. 6) It's a Buick Rear, not a Chevy rear 7) No need to change out rear upper control arms (I think Bob Christo had to do this because they are slightly different) 8) Parts availability is just as good if not better. 9) Probably more than enough rear for what the OP wants or plans to do with his ride. 10) Less trouble for a rear that's plenty strong Lemming huh? Coming to Atco Moishe?:laugh:
LOL...Ok now boys.... Just do not say 9" and then I will not get all bent out of shape...lol. :bla: 12 bolt 8.5 etc. Just make certain you built the rear correct and it will do the job.
Just pulled a 10 bolt out of a 71 skylark.....3.42 posi. will it have bolt in axles... I have it for sale for $650.00, Glenn
If it was the original rear, it will be an 8.5 10 bolt, and it will have bolt in axles. Lots of things get replaced in a car that is 40 years old. Post some pictures of the rear cover and u-joint retention.
So LarryGS,Are you telling me I should go with the 10 bolt? I was always told 12 bolt is better then 10. My GS currently has the 10 bolt in it but I also got the 12 bolt with it as parts. The current 10 bolt does not have posi, which i would like to add and i would like to go with 342 gears instead of the 308.Also, I was told it was a 8.5 but what is the easiest way to tell for sure? Thanks again.
The 8.5 is a good strong rear. Upgrade it like I did, with Moser 30 spline axles, and matching Eaton Posi. Look at the linked article in the post above. The lugs under the rear cover are a dead give a way. Also, the rear u joint will be retained by 2 brackets and 4 cap screws.
just pulled brake drums off and has bolt in axles and retainers you described... Must be worth more now.......lol........:grin: Thank you for all info... Glenn
A Buick 8.2 will also be bolt in axles. look for the squared off lugs on the bottom, and the brackets/cap screw u-joint retention. An 8.2 will use U-bolts and nuts.
I'll throw some fuel on this fire....:blast: Let us not forget the 71-72 Olds used the same 8.5" rear. And those all conquering 28 spline bolt in axles with tapered roller bearing first appeared on the 1970 Type O Cutlass/442 rear (available with a GM first aluminum center section). Lay a type O ring gear on the table next to an 8.5 or 12 bolt and you'll find it is larger than both (yea, yea I know Richmond calls it an 8.5 but the mark 1 mod 0 eyeball don't lie)....:bla: And lastly the 67-68 type O was available strait from Lansing with 31 spline bolt in axles. :bglasses:
No fire there... BARELY A SPARK...lol 'O' type is 8.4 and the actual ring gear tooth surface area is less than the 8.5 across the surface face. The strength does NOT come from the diameter of the ring gear (Diameter of the ring gear only bleeds off heat) NO heat in a drag race application... 12 bolt olds has the small 27 spline yoke diameter which is where its weak point is. 12 bolt chevy and 8.5 use the larger 30 spline yoke larger diameter outer bearing best for high torque applications. 1971 1972 the bolt in axle spline were changed from 60 degree cut to 45 degree cut. Will have to bow on the 31 spline 67 68 but you still have a pinion that is smaller diameter than your axle shaft which will be your weak link and if you can not get the power to the axles before the pinion snaps off... well then 31 spline axles are a moot point... THIS IS THE EXACT PROBLEM WHEN PEOPLE USE 35 SPLINE AXLES AND THE STOCK FORD 9" PINION SHAFT WHICH IS WAY SMALLER DIAMETER THAN THE PINION SHAFT...LOL Just remember this is all fun and hope no one is actually holding grudges... :beers2: :beers2: Jim JD
