diff swap

i have a 91 c1500 with a 350. i want to put a posi rear end in it and i have been told the z71 models have posi rear ends. i was wondering could i fit one in my truck

You probably have the 10 bolt rear end in it so it should be easy to find a locker or limited slip to put in it. Pick up a 4 Wheel and Offroad magazine, they have all kinds of websites where you can order that type of stuff. I have been thinking about adding a locker to mine since the limited slip doesn't work anyway.

Not all 4wd trucks had the limited slip. If you find a donor vehicle, check for "G80" in the list of RPO codes on the inside of the glove box door. Also keep in mind that the 4wd axle may be 2.5 inches wider than the 2wd.

Another way of checking for the limited slip is to spin one wheel of the possible replacement axle as fast as you can by hand. It should lock up after about half a turn.

James

Good advice. The lever/pawl type lockers don't respond to the old fashioned turning the wheel slowly to check rotation of the opposite wheel. You have to get enough speed on one wheel to generate enough centrifugal force to engage the locking pawls, just as JaVeRo advised.