So I just put a new distributor cap, rotor, and coil on and I went from one wheel peeling to both. Is it usual for a possible power gain from these replacements to cause the posi to kick in? I've always only had one wheel going in the past.

 

the easiest way to see, jack up the rear wheels and rotate one wheel and see what the other wheel does. you may have just had even weight transfer at that moment.

 

Since the car was originally a V6, I suggest that the rear is open. To verify, however, you might pop the cover and take a peek.

JamesC

 

Second easiest way is to change the diff like I did. It probably needs a changing anyway.

 

I think skirkland1980 hit it best. Not that JamesC is wrong, but probably no good reason to pop the cover at this point. Not that fresh lube would hurt anything.
I suggest that it's probably your original axle. If you like the gearing, then order yourself a conversion style locker for it. Then when that arrives, you'll have good reason to pop the cover and change the lube while you're exchanging the spiders for the locker.
Posi's wear out, they don't suddenly start working.

 

Hey there is a 99 percent chance that you dont have posi , but the good news is that you either have a 323 or more than likely a 342 gear ratio in that car! You lucky dog.

 

I actually like my open rear but i wish it was a v6 rear. As they are both the same exact car. The v6 came with a more disirable ratio though. I like my open rear cause the one to two shift really kicks the car out sideways with an auto trans.LOL

 

https://www.thirdgen.org/1985-pontiac-firebird

 

if you had 1 wheel spin before then you dont have posi, even with an open diff you can spin both tires if they both have equal traction, so now that youre making more power, youre giving both tires enough power to spin,

enjoy the new found fun!

 

Been a little while since I sold trucks, the open differential is different than a setup like the Eaton G80 locking differential right? Open is where the power goes to the wheel with the least resistance if I remember right, correct?

Seems like I probably do have the 3.42 differential which is good for the 305 it's paired with. I will get the lube changed after I'm done getting the car ready for inspection...I still have a little ways to go. I tried the spinning one wheel thing before and came out with some weird ratio that doesn't exist, I forgot what it was.