I just installed a 9 bolt disk brake posi in my 86 iroc. When i first got on it after the install the posi worked great, i parked the car and the next morning i backed out to the street and only one tire pulled. Well i drove my car around the block a few times and tried it again and my posi worked, it worked the rest of the day. I havent tried it yet today but what would cause it not to work the first few times. I got the rearend out of a junkyard 88 iroc, and its been sitting in my garage for about 6 months prior to me putting it in, is the fluid in need of a change or could it just be low becauase i havent even checked that.

 

just to make sure i understand this, you put in a rear end of unknown history and didn't pull the cover to inspect it first?

 

Maybe it's a little dry? Could this happen if the posi additive weren't dumped in with the last fluid change? I'd change it out anyway. It'll cost like $20 with the gasket & all fluids.

I have a similar issue. Mine still grips OK, but makes a ncie deep grinding/moaning noise that doesn't sound right...I think mine's just worn out -- mine's a junkyard piece as well.

 

I just took the rearend out of a junkyard camaro, and put it in my car. I didnt inspect it or even check the fluid, but im about to check the fluid level and fill it up to the fill hole. Its a 9 bolt rearend which dont generally wear out near as quick as ten bolts. And i figured even if the posi dosent work at least ive upgraded to disk brakes on the rear.

 

Any news?

 

9 bolts dont use posi additive. they dont have a clutch type posi. they have brakeing cones.

 

The cone-type doesn't use additive? I never worked with them, so this I had not heard.

 

Sheet fire! I hope you checked the brake fluid! They also make fluid especially for limited slip posi's. Useing the wrong fluid will result in poor performance. Look close at the auto store when buying fluid that states "for use with limited slip differentials".
Note my location! I also work in Dale, In.

 

all friction based posi's need posi additive. The GM stuff works the best. Only true ratchet style loclers don't require the additive. Generally, I use two bottles of GM posi additive with my factory cone type Auburn posi's.

On another note, you actually put a junk yard axle in without even pulling the cover? How do you know it's a 9 bolt with a posi if you didnt personally inspect it?

 

i havent been on the computer for awhile. The rearend does the same thing it always has sometimes the thing will rock my car left when i power brake it and sometimes it spins only one. The first bolt i went to take off the rearend broke off in the cover so i stopped right there and havent tried to take any more off. I know its a posi because its a nine bolt disk brake rearend, and as far as i know all the 9 bolts disk brake rearends were posi. I think im gonna get brave and try to pull the rest out without braking them but i honestly dont think the damn rearend cover has ever been off of this thing. So the fluid just might be really really old, that might cause it to do this i hope and i guess i need to get posi additive too.

 

sqzbox, my sister lived in ft.Branch for awhile and i stayed with her there. I drove my black 89 rs then. I am getting a job at toyota in a week, I drove through ft branch today on my way from mt carmel to home here at rockport. I drive a black 86 iroc now so you might see me coming through town every now and then.

 

Understandable. Since it's a 9-bolt, I may have done the same thing. Curiosity is really what made me open mine when I got it back from the salvage yard. I had this burning desire to make certain it wasn't toasted -- that and the yard near me drains all the fluids from the car before putting them out to be picked apart. Do you see any holes in the cover as though someone punched a drain outlet for the fluid? I'd recommend sourcing a new gasket before popping the cover off because the 9-bolt stuff may take a little longer to get. You should be able to get the fluid & gasket for around $25 or so. While you're at it, check the rear bearings & seals. If the bearings gave more than a little, it could let fluid drip out from around the seal. This would cause a low-fluid condition which could prevent the posi from functioning properly. Get some PB Blaster and hit each bolt once a day for 3-4 days prior to pulling the cover...and drill out and remove that broken bolt before pulling the cover to prevent metal shavings from getting in the diff.

Also...VERY IMPORTANT -- be SURE you're able to remove the diff filler plug before popping the cover off. PB Blaster once again will make it easy work, but could take a few days to fully penetrate/loosen the filler plug. I've heard some not so fun stories from people here who reconditioned their rear ends only to not be able to refill them with fluid because the plug was stuck. Eek.

 

I'll keep an eye out for ya! I drive 41 south and 64 east to dale mon-fri. between 2 and 3 pm in either my white 88 form. or my 03 black GP with twin ram air scoops on the hood.

 

The differential didnt appear to have any leaks or holes. There was a black valve cap looking thing on top one of the axle tubes that had a little grease around it but thats it. Im gonna quit being lazy one of these days and finish getting this cover off, but im definately going to make sure the gasket is in, because 9 bolts are hard to find parts for.