okay I have a 2001 chevrolet silverado 1500 with a 4.3 v6.. I want to buy a locker and 4:10 gears but dont know which one I have... Can anyone help me? I was going to purchase a detroit locker for 8.5" 10 bolt 30 spline... is this correct

 

If you're getting a Detroit True trac then the one for the 8.5 30 spline will work; you just need the install kit for the 8.625 rear. The rear end you have is the 8.625 but some parts are interchangeable.

 

Detroit Truetrac for $350 w/ free shipping, get the last one before someone else does: http://cgi.ebay.com/ebaymotors/Parts...1%7C240%3A1318

 

here are all teh Eaton traction aids.
http://www.eaton.com/EatonCom/Produc...iLSD/index.htm

I would go with the POSI/LSD that uses teh carbon clutches. Then you have traction to BOTH wheels at all times, instead of the being biased like the True trac. if 1 wheel is off teh ground, the Truetrac is useless unless you jam the brakes hard.
truetrac is excellent for a street truck, thats for sure, for more even burnouts and more equal power to BOTH tires, go LSD/POSI. For the ultimate 50/50 split/drag racing action go with the true Detroit Locker or E locker.

peace
Hog