Just thought I'd help clear up a few things about S10 donor parts (specifically brakes and rear ends.)
- GM made the 10 bolt in S/T-Series in a few different sizes - 7.5, 7.625, & 8.5. Identifying between these diffs is fairly easy work if you use the following tips: The 7.5" / 7.625" will have straight axle tubes, 8.5" should have a diameter change about 3" from the center section. Also, there are identification markers are on the bottom of the center section. The 7.5" and 7.625" will have two "fangs" that extend down from the housing, about 3/4" long and about 5" apart. They look like little triangles or cat's teeth (long slender & sharp). The 8.5" rear has casting lugs in the same location, but they're big rectangular blocks (like 3/4" or 1" across the face). Very easy to tell the difference. Check this link for a pic of the axles -
- The 4WD axle is about 4" (overall) wider than the 2WD axle, and the ZR2 axle is about another 4" wider than the 4WD axles (about 8" longer than the 2WD.) If a 2WD axle would require you to run 2" spacers, try the 4WD axle. Also, AFAIK, the ZR5 has the same axle width
- You could get the 8.5 (the strongest of the S/T axles) from a number of donor vehicles, namely, those with a V6 and MT (also, ZR2s only came with an 8.5.) However, this doesn't mean every V6/MT truck will have an 8.5. Use the tips above to verify which rear is in your donor.
- Each of these axles came in a variety of gear ratios. If your donor has the RPO code sheet (located in the glove box) intact, you can get the ratio from there. Look for one of the following codes:
- You may have noticed POSI-TRAC listed above. Don't get too excited just yet, because GM used the Eaton Gov-Loc in all of it's S/T posi rear ends. While this is better than an open diff, it cannot measure up to the performance of some OE posi units or an aftermarket posi. The Gov-Loc requires about a 100 rpm difference in axle speeds to engage, so you basically have limited spin instead of limited slip. Then, once you get over 25mph or so and lift off the throttle, they unlock and won't relock until you slow back down below 25mph. Also, if you grenade a posi rear end, it will usually take the whole diff with it. So, consider your power level before paying extra for a posi'd diff.
- 97 and earlier S/T axles had drum brakes, while 98 and later had 11.5" disc brakes.
- Also, one of the great things about using GM parts is that SO much is interchangeable. For the S/T trucks you have the luxury of being able to use F-Body (Camaro/Firebird) and some Y-Body (Corvette) stuff when it comes to brakes. That said, a common upgrade for S/T trucks is to use the 98 and later F-Body rear discs (which bolt right up and only require modifying the parking brake cable) and upgrade the front discs.
- For the front discs, you can go with later model S/T brakes (IIRC, 98 and later have dual piston calipers and a 1" larger diameter rotor), F-Body brakes, or go aftermarket (CBR, Baer, etc... have kits.) Keep in mind that you may have to run 17" or larger wheels with some kits.
I'm sure there's more that will come to me later, but hopefully this will help some of you guys for now. A few links are below for those wanting more info: