ok heres the deal....i know that the lock right units only replaces an open carrier, but my rear-end has been acting funny. its never spun both tires in the 6 or 7 years its been in my family until about a month ago when i drove around for about an hour and then did a burnout. it spun both tires for a couple seconds and then went back to one tire spinning? what gives?!?!?! is it just a really, really worn out posi or was it just a fluke? i don't want to buy the powertrax unit only to find out that i do have a posi. could someone enlighten me?? thanks (sorry its so long)
-jay

my bad.... forgot to mention its a 69 8.2" 10 bolt with gears somewhere in the two's, probably a 2.56 but never checked for sure...and i seem to recall that you could check for a posi by jacking up the rear and spinning a tire and if the other one rotates the opposite way then its an open diff or something along those lines...i can't remember?

Your's is probably open. On rare occassions, when the stars and the moon are in the right alignment, an open rear end will spin both tires. Lift the rear and spin one tire. If the other one goes in the opposite direction, it is open. If they go in the same direction, it is posi.