Originally posted by amc
my friend has a 97 firebird and he wants to know if it has posi or not. We saw on a sight that it has limited slip, but when he burns them both tires spin right off, rather than just one or one and then the other. thanx
That would be your 1st clue, a posi transmits power to both wheels, the idea being that under "normal" driving conditions if one tire loses traction the other will still bite and maintain forward momentum like pulling up a snow covered hill. If your friend does a burnout and both tires spin then he either has posi (limited slip, etc.) OR he has his suspension extremely well tuned with just the right amount of preload on the right rear. My guess would be he has posi.
There should be a tag on the differential indicating to use posi lube or you can lift one of the rear tires off the ground with the car in neutral and try to turn it by hand. If it won't turn:
A) You didn't put it in neutral. :o
B) One of your friends is being a wiseguy and set the park brake.
C) POSI !!!