70 GS buick rearend

[Andy Gargagliano]

Hi everyone.I am looking at a rearend out of a 70 Gs Buick.Ad says new 3:73 gears,axils,bearings,and auburn posi unit 800.00 or best offer.Does that sound good? Will this fit in my 72 Monte? Are there any modifications that will need to be made? thanks for your help. Andy

[Montemedic]

800 dollars is a fair price for what you are getting. The housing is the same and will bolt right in. 3:73 gears are a nice street gear if you are using the car for street and occasional track use. The axels are thicker and stronger than a Chevy 10 or 12 bolt. The weak link is the Auburn posi unit and cannot be rebuilt. If your purpose is mainly street driving with a lower HP engine, 450 or under. This should serve you very well. If it needs to rebuilt down the road, most rebuilders are installing a much heavier duty Grand National posi unit for racing use. It all depends on your needs and use will be.

[Andy's Auto]

I would jump on that like white on rice. An 8.5 can handle some serious power, even in a heavy car. You can build a 12 bolt for around $1200 but a 8.5 is just a tick not as strong. I personally like Eaton clutch poso units as the rebuild kits are less than $80 and I don't think I have changed them in my Malibu in 15 years. Mosers or Strange axles are a must. Two advantages. Strength and a nice new surface for the seals to ride on.

[Montemedic]

Are you sure the rear you are looking to purchase is an 8.5 ? The 70 GS came from the factory with an 8.2. The 71-72 came with an 8.5. The 8.5 is a stronger rearend. I discussed this with my neighbor who is a Buick fanatic and guru. He owns a 70 GS Stage 1, 4spd and swapped his factory 8.2 with a 3.64 posi to a 71, 8.5 rear with 4.10 and a Grand National posi unit. The GN posi is an Eaton style posi unit.