OK lets have a conversation on 9 bolt VS.10 bolt I think 10 bolt is the only way to go, add a 4th gen Torsen unit - no cones to wear out! whats your take on strength? I see it as a moot point 7.6 /7.75
then parts availability the 10 bolt wins that too and its easier to service
I've had a 3.27 9 bolt -never any issues with it, I went back to 10 bolt added 28 spline axles and Torsen no issues with it either, I know you can get factory GM gear sets as low as 4.56 in some Isuzu Pup's and 3.73 are common in S10 4x4s

 

Stock for stock the 9-bolt. Ive shredded several ten bolts in the past but my 9 bolt held up to the abuse again and again behind a very strong built 350 in my last car. But..28 spline axles along with the 4th gen Torsen would be the way to go for parts availability if nothing else. Id probably rather have the Torsen.

 

9 bolt with the diff upgrade..

 

Dumb debate. Both are weak, and neither is better than the other...

 

9 bolt with the Australian Torsen. 10 bolt's have the bearings running directly on the axle. 9 bolt has the higher spline count axles no matter what year it is.

You can find good used gears in a variety of ratios and the 3.70's are available new.

The cone type are garbage on both of them.

Both are frankly a poor choice for really high power but you can abuse the 9 bolt more and the Torsen makes it a good cheap option. Mine has been flawless with the Torsen and 3.70's

GD

 

9bolt for sure. Look at my sig, I raced on it for 20yrs. Posi wore out, but it never broke.

 

I have had both. For the cost of the parts to change gears on a 9 bolt I can buy 2 or 3 complete 10 bolts with the ratios I want. Also LS1 rear brakes are a bolt on swap for a 10 bolt. That said if your doing hard launches neither one is good. But on a road course either one is good. I just find the 10 cheaper and easier to get parts for..

 

Ok yes I know neither rear will hold up to decent power and traction but for the most part on the street with street tires they work fine I did the other day buy a 9 bolt that was in a 90 formula and it had PBR brakes on it shouldn't these have a splash shield or backing plate on it?

 

Only the early 89 9bolts have the 2 piece caliper bracket. Be glad you have the thicker 1 piece part. The car must have been a early 90 (most were made in 89) or the rear was swapped in, did you find the rpo code decal to see which rear it had?

 

code says GU5 G80 same as my red car

 

Pretty sure GU5 is a 3.23 10bolt. So guessing that someone swapped in the 9 bolt from a later 89.
My friend has a 90 formula with a 10 bolt and it's the 2,xxx th car built for 90. (even though it was built in 89)

 

took my 9 bolt partially apart- did you know carrier caps are retained by 3/8" bolts? no wonder people want support covers on these
10 bolts have 7/16" bolts for carrier caps