i Have a 1986 Z28 and i was wanting to know if the 10 bolt rear it has is either a posi or limited slip. Is there a way to tell other than taking off the cover? I was just wondering. Thanks guys. Also i dont know much about rear ends so thats why im asking -Matt

 

Same thing, just spelled different....Sure... take off the cover. Probably not though, but who knows, you might be lucky.

Changed the rear end fluid lately? I thought not... so while you're catching up on the long-overdue maintenance, make a point of looking at what's in there. The fluid change makes a great excuse for popping off the cover, and changing it might even get you better gas mileage, if you put Mobil1 or other high-quality synthetic lube in it.

If you don't know what you're looking at, take a pic and post it, just like the other guy I answered this same question for a couple of minutes ago; make sure you use the flash, and show the innards of the carrier through its window.

 

i was wondering because i have seen the long black marks where it spun both wheels like crazy... so wouldn't that say somthing? also how hard is it to change the fluid? thanks -Matt

 

Not really.

It's pretty easy. You pop the cover off (10 bolts), and the fluid falls out; put teh cover back on, and there's a square-headed plug on the pass side, that's where you add the fluid.

If it does turn out that you have posi, put in a bottle of the GM limited-slip additive first; then fill it the rest of the way up with fluid. Use 75W-90 or 80W-90, not the super-thick kinds like 85W-140. Should take about 2 quarts total.

 

not sure if it means anything but when i swapped out my gears nd limited slip the guy said to put in about 1/4 of the fluid in first then the bottle of additive then the rest of the fluid... probably means nothing just figured id add my btw a good test to figure out if you have posi or not is make a right turn... not left and get on it if she kicks out nd slides around the corner its posi if it lights 1 up its open... do it slow if your not used 2 puttin her sideways... like from a stop... just another good luck!

 

ya posi and limited slip are the same. thats what u want tho! i guarantee your rear diff is an open one. so if u burn out and only the passenger rear side leaves burn marks, then u have an open. if it leaves two burnout marks, then u have limited slip (GM calls it Posi). Im in the same boat and trying to find out how to put an LSD in mine, or how hard it is to do it. if u wanna check out Strange or Eaton, apparently the sell LSD's that can just go in but like i said, im still not too sure how that works.

 

oops! didnt see your second comment! well ya it sounds like u have posi. but changing the rear diff fluid is easy! takes about 30 minutes!

 

thanks for the replys, once i get the car back on the road my dad is gonna test the burnout mark theory and i will also change the fluid but when we looked at it the first time i didn't get to go because my dad went with the guy. The guy drove and as i was talking to the woman who turned my life inside out.. I heard tires screaming and the woman started laughing and said here they come.. about 30 seconds later they came around the corner... my dad got out and said you aint getting that car lol well we see how true that was. Any ways on the way home he took me back to the road where the guy had gotten on it and showed me the marks that were left on the highway they were like 70 ft long and i swear i recall seeing 2 of them but that was almost a year ago. it was like 3 months after that day that we bought the car but im 99.9% sure there were 2 of them. I hope so because that would be sweet! -Matt

 

you can also just power brake and burn em. that should let u see how many marks it leaves without having to drive back and look. just step on the brakes and then slam the gas!!!!!! its fun but it f***s up your rear brakes a lil.

 

yea i have no plans of abusing her after the hard life that she has lived. They drove it in the ground. I might just get in my drive way and stomp it and see how many ruts it leaves. (gravel drive way) afterward i hope to have some raking to do lol

 

ha ha! ya i got gravel too. well hell man, now is the best time to give her a lil hell! and fix her up even better along the way! mine is pretty old too but still has *****! and with every little mod i do, she keeps getting tougher. have fun with it man, just dont total it! fix it up like a dream and u will be happy with it forever! they are awesome cars man.