CUTLASS SALON REAR DIFF SIZE

[crucial118]

What's up guys? I have a 1986 Olds Cutlass Salon. Want to upgrade the rear end this winter, after I drop in my 350 motor, but I do not know which way to go. I know everyone suggests a Grand National, 442, or Monte SS rear, but they are outrageous in price. What size come on the Salon....7.5 or 8.5? Wouldn't it be cheaper to buy a diff unit and ring and pinion package from Summit?

 

[Phoenyx]

If it's original, it will be a 7.5. And I suggest you find something else. I have put well over $2000 into my 7.5, and if I could go back in time I would have just bought something else.

 

[86Cutlass383SR]

Only the Buick GN and the Olds 442 (H/O's maybe too ?) had the 8.5 rear end. All other g-bodies had the 7.5.

You can buy an 8.5 for between $600 - $900. Have someone look at the differential and maybe install a posi. Might have new aftermarket axles in it. Add about $800 for posi and axles if needed.

You can also do 12 bolt, Ford 9", or a Strange Dana 60 that is a bolt in for the g-body. Figure close to $2000 for a complete ready to bolt in rear counting housing, posi, axles, (and carrier for the 9").

Depending what kind of power your 350 will be putting out, I'd say the 8.5 is still the best option if you can find a good one. Usage is also a factor. Is it a daily driver? Slicks or drag radials? If you're not going to be beating on it much I'd just leave the 7.5 in it. But if you have a posi and axles put in the 7.5 you'll almost have the 8.5 paid for.

 

[crucial118]

Thanx for the info.

 

[Phoenyx]

Just wanna add this. I have broke about five 7.5s over the years. With either stock or very close to stock engines, and this was on skinny street tires. So just don't waste your money on that 7.5.

 

[RITTER]

Alright, we get to start the 7.5" and 8.5" debate again

Had nearly 20 passes on a 7.5" 4.10 gear GM posi unit and Moser axles in my '81 Malibu 327 w/nitrous ( low 12's )
the same exact rear that my friend pulled from his Monte with a 355 with Canfield heads with the same nitrous setup. And after we pulled it out of the Malibu it went into an '84 Cutlass with a flattop 46x cubic inch Olds. All of which had slicks on them at some point.
IMO, unless you are running a 10 second quarter mile, the 7.5" rear with some gears and either a spool or posi unit will be just fine for you!
But....on the other hand....if you are planning on buying a ring/pinion and a aftermarket posi unit and axles and installation kit for your 7.5" rear and then paying to have someone do it ... you are going to spend more than you would to just go out and buy a complete low mileage GN/442 rearend

 

[nawlins-tim]

Hey the Buick T-Type turbo had the 8.5 too.

 

[Phoenyx]

So I guess 305s and 301s can do 10 seconds on street tires then?

 

[RITTER]

So I guess 305s and 301s can do 10 seconds on street tires then?

HA...negative!

But it sure wasn't hp that broke the rearend, it was either high mileage or a faulty part mechanically or just low/old fluid

 

[Phoenyx]

I've had 2 that were rebuilt go on me, so it's not that.