It's a stock 1985 Z28 with 305ci 4-barrel and stock th700r4 tranny, do I have a posi on it?

 

Maybe. Best way is to just look. Your differential fluid probably needs to be changed anyway.

Welcome to the boards, btw.

 

Look inside your center console. There should be an RPO code tag either on the side or on the bottom of the console lid when you open it up. If you see the code G80 than it came with posi. Its also possible that someone could have swapped it in also though.

 

The Code Tag is missing. Anywhere else it might be?, or do I have to go look?

And yeah it probably needs to be changed anyway.

Thanks for the welcome, you guys seem really helpful, unlike other boards i've been too.

 

Forget the codes. They only tell you what the factory put there, not what's there now.

The tag is somewhat less unreliable, but still not infallible.

The "2 stripes" method is a joke.

Take off the cover and look; it's the only way to know for sure.

Have you chaged the fluid lately? Then you need to. While you're catching up on the overdue maintenance, make a point of looking at it and seeing if it's a posi. And count the teeth on the gears, then you'll know for sure what gears are in it.

 

Thanks guys! I'll take a look when i get it up on the rack this weekend.

 

Yea but its an excuse to do a smokey one

 

Pick the car up on a lift and turn one of the rear wheels. If they turn the same direction, you have a posi. If they turn opposite directions, you have limited slip. (At least this is how I check...)

 

Not limited slip, an open rear, posi and limited slip are the same. Posi-traction was coined by some GM division in the 60's (Pontiac I think on the GTO/Lemans maybe).

 

Wasn't "posi" short for "positive-traction"? I thought it was the 50's...

My bad with the terminology, but you get the point...