Buick Grand National Posi under 1986 Cutlass Supreme?

[YaoGuaiCutlass]

Okay so I have 1986 Cutlass Supreme Brougham that I have been working on for a few years now. Up until a few months ago it was a daily driver with a LSD (Limited Slip Differential) rear-axle. My buddy recently was in a wreck with his 1986 Buick Grand National and decided to part it out instead of restoring. He sold me the rear end for $85.00 and said it would work for my Cutlass. I am putting a 425 Super-Rocket in my car with a turbo 350 and want something with a little more race edge to it. Will the Buick rear end work? Will I need to do any modifications or buy anything?

The Buick rear end is a Grand National. 3.42 ratio with G80 Posi-Traction. 8.50" 3.42 Posi Rear End. Has 12mm studs on it if that helps any.

Please let me know, Thank you!

 

[Qdub24]

It's a direct bolt in replacement for your rear. You may need the driveshaft as well.

 

[YaoGuaiCutlass]

It's a direct bolt in replacement for your rear. You may need the driveshaft as well.

Would the Cutlass drive shaft work or would I need the Buick one?

 

[Qdub24]

The car's make doesn't make a difference. I think the driveshafts are different lengths.

 

[YaoGuaiCutlass]

The car's make doesn't make a difference. I think the driveshafts are different lengths.

Okay, I'll check their lengths and see. Thanks 🙂

 

[MrLightning]

You STOLE that rearend for $85.00.....................that's a $800.00 rearend any day of the week otherwise. Yes, you will need the driveshaft from the Buick Grand National and its a direct swap into your car with the Grand National 8.5 rearend.

 

[olds307 and 403]

I wish my friends were like yours 😀. That is a very good upgrade for the torque of an Olds 425. I blew the spider gears with my 403, punched a hole in the girdle cover and destroyed the pinion. The spiders on the 7.5" are a known weak spot. Very good score.

 

[Bweavy]

The car's make doesn't make a difference. I think the driveshafts are different lengths.

The 8.5 housing being larger you will need the 8.5 drive shaft. It is shorter the your 7.5 drive shaft.

 

[dan aughtman]

Almost an inch shorter and look closely at the rear yoke and universal joint sometimes they are different. I have a 1978 Malibu and the universal was different!

 

[V6UnderPressure]

If you are looking for a driveshaft, I have one off of my GN for sale. Drop me a pm if interested.