Gear questions?

Discussion in 'Got gears?' started by bigtimer24, Apr 8, 2023.

  1. bigtimer24

    bigtimer24 Member

    My kid and I are working on a bit of a Frankenstein 68 Buick Skylark. It has a Chevy 350, TH350 Tranny, and the original 10 bolt 8.2 bop rear end. Should we upgrade to a posi and if so what gears would you recommend. It’s going to be a daily driver but wouldn’t mind the occasional burnouts for fun. Definitely won’t be a strip car lol. Thanks in advance.
  2. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    There are NO new gears available for the 68-70 Buick ONLY 8.2 10 bolt. Years ago, a company called Fabcraft reproduced the 3.42 and 3.64 gear sets. They should be making another run, but no one knows when, last I heard.

    Everything is more expensive for this abandoned rear, as you might expect.

    The best option is to swap in another A body rear. The 71-2 Skylark/Cutlass 8.5 10 bolt is a great swap and aftermarket support is plentiful.

    You can also swap in the earlier 64-67 BOP 8.2 10 bolt . Do not mistake the 1968 original rear in your car for the earlier 64-67 BOP 8.2, they are DIFFERENT rears. A lot of parts houses don't know that.
    Last edited: Apr 8, 2023
    FLGS400 likes this.
  3. Mark Demko

    Mark Demko Well-Known Member

    What gear is in it now?
  4. BrianTrick

    BrianTrick Brian Trick

    What Larry said is accurate. The 8.5” 10-bolt from a 71-72 Skylark/GS or Cutlass/442 is the most logical option. Plenty of parts available and one of the best rears ever made. The only thing you will need to do is shorten your driveshaft 3/4”.
  5. pbr400

    pbr400 68GS400

    I think you need to ‘Buick’ the chevy parts, and ‘chevy’ the Buick part. Put in a Buick 350 or 455, BOP T350 or T400, then put a corporate (chevy) 10 bolt from a ‘71-2 A body, with 3.xx rear gears.
    PGSS, Waterboy and rkammer like this.
  6. monzaz

    monzaz Jim

    Sent you a PM
  7. bobc455

    bobc455 Well-Known Member

    To answer your question - in that case I wouldn't bother with posi. The ratio I'd choose depends on how much highway driving you'll be doing, if you do a lot of highway then a 2.56 gear makes for an awesome trip (and the 350 has plenty of torque to handle that too).

    -Bob C.
  8. inverse121

    inverse121 Well-Known Member

    Hoping I can drop in without a hijack since I think its related.

    My 1971 El Camino came from the factory with a 2.56 8.2" BOP rear. This is evidently not uncommon and in fact when I look up parts on NAPA, this is one of the questions to confirm which parts fit such as ujoints and drum brakes. Are parts (gears and carriers) available for this rear end? I see lots of parts online, but I am not knowledgeable enough and Larry's comments above give me concern.

    My 350 is weak and while it ran out fine on the highway, it couldn't pull the 2.56 gears on the backroads and hills very well. I swapped in a Chevy 3.08 posi complete rear end resulting in much better driveability and improved gas mileage as it wouldn't lug down on a hill anymore, but I'd prefer to go back to the original rear end with bolt in axles and bigger ujoints with more gear.

    To answer OPs question, I don't know that the posi will add anything for a cruiser other than bench racing and cutting up. When I was a kid, I put the posi to good work smoking tires on Friday and Saturday nights down dead end roads.

    Just be certain to get the gearing right as mine is much more enjoyable with the 3.08 over the 2.56 with actual mileage improvement as the engine doesn't have to work as hard to pull the load.

  9. LARRY70GS

    LARRY70GS a.k.a. "THE WIZARD" Staff Member

    AFAIK, there was no BOP 8.2 10 bolt in 1971, and the 1971 El Camino should have come with a Chevy 8.2 10 bolt. In 1971, GM went to the 8.5 10 bolt. There are no new gear sets for the 68-70 Buick only 8.2. There are plenty of parts for the earlier 64-67 BOP 8.2's. You need to positively ID the 8.2 you have. Are you sure it is bolt in axle?
    Last edited: Apr 19, 2023
    john.schaefer77 likes this.
  10. inverse121

    inverse121 Well-Known Member

    It’s for sure a BOP 10 bolt. It has bolt in axles and the big yoke.
    There seems to be some evidence that 71 El Caminos could have come with a Chevy or a BOP rear. I’m pretty confident in the provenance I have on the car.

  11. BrianTrick

    BrianTrick Brian Trick

    Pontiac continued making the P-type 8.2” all the way to 1972. The rear that inverse has picture is a P-type 8.2”. If it was born in that car,it would have a Chevy code on the tube and dates to match the production of the car. There are gearsets and posi units available for that.
  12. inverse121

    inverse121 Well-Known Member

    Thanks Brian
  13. monzaz

    monzaz Jim

    I know 1970 GM car came with P rears from the factory FOR SURE... All parts books even prove that. I have a factory Monte carlo 1970 with a P type rear 2.78 open...REMEMBER there was a strike in 1970.
    But I do not know how far that went into the early 1971 production car which usually start at least in October. It might be possible...
    Anyway It is all a moot point as your just dealing with what you have and that is all that matters.
    SO a Chevy rear or a Pontiac rear.... It is all good. The Chevy rear you can get 3.08 gearing NEW. The Pontiac rear YOU CAN NOT. 3.36 is the best you can get for freeway for the aftermarket gearing.
    SO if you like the 2.56 gearing you had better look out for gears on line and buy them when you need them... Nothing NEW out there.
    I do not understand if your 350 is stock it should have plenty of torque to move the car with any gear.
    You think anyone changed the cam? Ir maybe the distributor advance is junked out? Or timing is off?
    JD Race
  14. BrianTrick

    BrianTrick Brian Trick

    You can install Chevy 8.2” gears and posi into the P-type housing. There is a special pinion seal needed to do it. I have done this a few times for customers. I have the seal number here somewhere… You will also need to use the Chevy 1310 yoke with the Chevy gears due to the spline count.
  15. monzaz

    monzaz Jim

    THIS Chevy into BOP works for the BUICK 8620 seal housings 1964-1967.
    You can use a standard Chevy seal in the BUICK 8.2 housing with a Chevy 25 spline pinion pinion and yoke.
    I have also done this with Pontiac 8.2 rears and a Chevy 25 spline BUT we had pinion yoke seal bushing made to make it the size of the 1.94 (2043 seal that is for the Pontiac housing.
    So you would press this doughnut ring onto the Chevy yoke to make the seal surface 1.94 same as Pontiac.
    We did this when the first gas price hit way back and we were installing 3.08 gears into BOP housings.
    We also used the yoke spacers to save Pontiac and Olds housings that lost the YOKE. We would use 7.5 yoke with the doughnut ring pressed on and mill some done off the yoke bottom as the 7.5 yoke was a bit on the tall side.
    THERE were so many thing I did when I first started out...To make a name and solve issues. When I forst started this i thought there was not anything that could not be solved. :)
    I was YOUNG then.... LOL
  16. BrianTrick

    BrianTrick Brian Trick

    The one I did local was 8.2” Chevy guts into a Pontiac 8.2” housing. I did not use a bushing or adapter. There is a seal that works,or at least for the housing I used.
  17. monzaz

    monzaz Jim

    Only seal I found for a PONTIAC conversion to chevy pinion and yoke was a crappy one lip seal years ago...That is when I just made some press on collars at my machine shop. Told them what I needed they whipped them out. I think i still have a few on the shelf.
    Last edited: Apr 25, 2023
  18. BrianTrick

    BrianTrick Brian Trick

    Depending on housing bore,you could use the National 8610,which is fairly well-known,or the 770077. I believe I have a 3rd one. I know I kept the box.
  19. monzaz

    monzaz Jim

    That is the seal for the Buick 8.2 WILL not fit the Pontiac 8.2 housing 770077 ?? Do not know of
  20. BrianTrick

    BrianTrick Brian Trick

    I didn’t use the 770077. I used a different one. I will find it.

Share This Page