OK ... so I'm digging around in the junkyard, looking for parts for my Sonoma/5.7 Vortec conversion, when I spot what looks like a _really_ flat S-10. It turns out to be what's left of a 1992 GMC Syclone! At the end of the day I have a truckload of parts, including the complete rear end. I bought this because it was cheap ($180) and I assumed it was stout enough for the mouse.

Now, of course, I'm wondering what I've really got. I know its a 7 5/8" rather than a 7 1/2", and I counted teeth and it looks like it pretty close to 3.42. I think I can see a clutch pack inside so its probably a posi, but it also seems to have a little centrifugal pawl that locks it up, too. Its a little wider that the rear end that came in the Sonoma, but the spring mounts are identical and it bolted in OK; the tires just stick out an inch or so on each side.

Can anyone tell me where I can get more info on this thing? I'd like to know who made it, just how much power can I run through it, can I rebuild it, was I a dope to buy it, ... you know, stuff like that!!

you should be ok. the unit is a posi, gm's later model units all look like that. gears from a 7.5 will fit. lots of automatic small block s-tens running around with that rear including mine.(3.73 auburn posi)

[ November 17, 2002: Message edited by: BOBCRMAN@aol.com ]</p>

Bluesman, I'm new to this board but have done alot of projects for hire like your doing. First off I = hear this type of question on this board all the time. I feel the real question is will it hold up with a set of slicks on at the strip. NO. If your going to run street tires and are ok with some wheel spin then it should be fine for a long time. When guys are looking at the strength of a unit gearing, car weight, traction and intended use need to be a big part of that question. Back before everyone and their dog had a v-8 s-10 I had a D 50 with a 340 in it. I used the 4 banger rear and never had abit of trouble. Having said that I never had it hooked up either. Your rear you picked up has the same parts inside as the Grand Nationals do. They have ran those things into the 10's with the stock rear so I think you'll be fine for a strett ride. Ryan

[quote]Originally posted by bluesman123:
<strong> it also seems to have a little centrifugal pawl that locks it up, too.</strong><hr></blockquote>

Thats a GovLoc differential, garbage, I've never seen one that wasn't broken.
Did you get the AWD stuff out of the cyclone? That would have been the way to go. You can also find the same drivetrain in Oldsmobile Bravada's.

You do in fact have a 7.625" 28 spline 10 bolt with a Gov-Lock. This is the same rear used in the regular 4X4 trucks as well (they are 2" wider than a two wheel drive). The 7.625 was used in the LS1 Camaro with a 6-speed. In stock trim, the LS1 could put 300 HP "on the ground". This should allow 12 sec passes in your S truck without problems. The Gov-Lock posi unit is a wonderful thing....On paper. It was designed to lock when there was a 100rpm differance in wheel speed. Then, at about 30mph it would un-lock as to not have any effect on handling. In the real world, they where complicated and broke easy. That and the fact that a posi locking and unlocking during a high power, high speed run was for the birds. I think the Auburn is about the best unit for the 7.625. Very pridictable and strong. Another mod that should be concidered is a girdle. The 7.5/7.625 will break from housing flex. The more power, the more it will flex. This flex allows the gears to move around changing the mesh and contact points. Unless you compleatly over power the thing, you will have premature gear wear as a sign you need a new stronger rear. The max limit on a good 7.625 is about 350hp and 400tq as measured at the wheel. Dan

FWIW, The Grand Nationals used an 8.5" 10 bolt. Whole different ball of wax.

7.625 Grand National rear. Use to have one. My mother bought it new. But hey who cares the thing will work.

You guys are great!! I've learned more from you in 24 hours than in days of web searching.

Big Thanks!!!