quick90rs

iTrader: (3)

So i was bored today and decided to try a little burnout i stepped on the brake and put my foot into the throttle about half way with my camcorder on my phone set, only the passenger side spun and the drivers side did not. I know it is a posi (limited slip) because when i purchased it and put it in i purchased a posi it had the clutch plate and the two wheel burnout would always happen. It was wet outside today. Can anyone explain this for me?

Big Matt

Maybe your posi is worn out. They don't last forever from what I've been told.

quick90rs

iTrader: (3)

besides that how could i tell if its worn out? it feels good from take off and doesnt feel wrong she takes right off. Could limited slips just spin one wheel sometimes? also, if a posi is worn out and i get the rear in the air and spin the wheels will they spin opposite of one another?

quick90rs

iTrader: (3)

Im just worried if its worn i want to take care of it ASAP, if i do have to change it and this is not normal because of the wet road or something what size is the carrier (7.5? 8.5?) , how many splines are my axles (28??), and i have a 10 bolt right what series should i be looking for ( a 3??) ? it a 90 camaro 305

redneckjoe

try doing some real low speed figure 8s in a parking lot. it will break the varnish loose on the clutches. post your results. it worked for me. checkout the before and after pic. lol.

quick90rs

iTrader: (3)

Well if its worn out its worn it usually always does dual wheel though? It was a half throttle burnout nothing crazy is it possible just the one wheel spun?

FireDemonSiC

Are you using the posi additive? Have you changed your gear oil recently?

quick90rs

iTrader: (3)

havent changed my gear oil since putting the rear end in a few years ago, put some Lucas in it with the change thats all

FireDemonSiC

Depending on what additive you used and how much it can negatively impact lockup. Believe it or not, the purpose of the additive is to REDUCE the gripping effect of the clutches to help eliminate posi chatter. It's a trade-off. either use no additive and get maximum lockup but with faster clutch wear or use additive and get reduced lockup with longer clutch life. However, if it had been working fine all this time something is def up.

I put Amsoil 75w90 severe gear oil in my rear (No homo ) with no additive and am very pleased. Only time I get chatter is going around a corner in 1st if It's wet outside (I think this is actually the clutches grabbing and the tires slipping against the pavement) or if I get on it in reverse.

quick90rs

iTrader: (3)

what are your suggestions on what i should do to fix my problem? a fluid change would help? what should i put in it? i just want this fixed lol, i dont want to pull that diff i had money saved to do some other stuff

FireDemonSiC

Try what redneckjoe said. TBH I'm not too wise on worn posi units. I just had mine installed last november so haven't gone down that path yet.

quick90rs

iTrader: (3)

Thanks, if anyone else could throw their 2 cents into this id appreciate it

FireDemonSiC

How many miles on the posi? Was it new when you installed it?

Also something every clutch type posi owner should know is that under NO CIRCUMSTANCE should 2 different sized wheels on the rear axle ever be used!!! If you have a flat or a blowout, DO NOT use the donut spare. Tow that bitch home! Driving with 2 different sized wheels will constantly slip the clutches and burn them up very quickly.

quick90rs

iTrader: (3)

it was not new and had no idea how many miles

quick90rs

iTrader: (3)

i'm basically going to have to face the fact that i need to replace my unit. What i need to know is how many splines are my axles? what size is the carrier ? 7.5? pretty sure its a 10 bolt, how many splines on my axles and what series carrier? what years and cars had these? all specs i need to i can look for one, thanks guys

FireDemonSiC

Count the bolts on the cover to know what rear it has. I'm not sure if the 9 bolt borg warner rear was an option in 92. To know how many splines you have you gotta pull the cover and look. If you have a clutch type posi (And not an Auburn cone type) they are rebuildable. You don't have to replace the whole unit. Also the 4th gen zexel torsen carriers will swap right into our cars. They use a worm and sector gear instead of clutches or cones so they will last indefinitely until you break it (They are rather fragile when it comes to heavily modded cars).

The rear in my car came from an 89 and when we built it it had 26 spline axles. Swapped to 28 spline forged.

quick90rs

iTrader: (3)

stock in 10 bolt 90-92 rear end what are the number of axle splines and the carrier size and all that info

redneckjoe

seriously,...try some low speed figure 8s. change the fluid. you will see a difference. drive it hard!

FireDemonSiC

By the 90 - 92 era I think they were using only 28 spline axles. Don't quote me on that though.

SCCAjunkie

Check the posi unit itself first.

1) Jack up both rear wheels, car in neutral. Spin one side. If the other side spins in the opposite direction, your posi is gone (or was never there). If they both spin the same direction, go to step 2.

2) Jack up just ONE rear wheel. Try to spin the other. If it doesn't spin with just a little force, try harder. If you can make it spin somewhat easily, your posi is working, but not real well- try the above suggestions. If it takes a LOT of force to spin (or can't be spun), your posi unit is working decently.

If you have a non-preload Torsen, the above does not apply, but you should be able to see it pretty easily if you pull the diff cover.

No matter what type of posi unit you have (other than a locker- and a spool is not a posi), it is possible to spin just one wheel if the torque differential is high enough. If you put one wheel on decent pavement and the other on a very slick surface and mat the go pedal, you can get one to spin. Once you exceed the breakaway torque (the "grip" internally in the posi unit), that one can spin, and it takes a bit of backing off until you get the slippage to stop. If you have a posi, eventually the available torque will be less than the breakaway, or the posi clutches may heat and find friction, and things will grab. Put too much heat in a clutched posi though, and it'll glaze like any other clutch, and that breakaway torque will be drastically reduced.

ramicio

iTrader: (-1)

Uhh why would the wheel not spin in the opposite direction? There are still spider gears inside the thing. Spinning it by hand is not enough of a speed difference to lock up a differential.

sofakingdom

iTrader: (1)

You must only know about S trucks, with those weenie Gov-Bomb things.

An actual POSI has clutches or worm gears in it, that are ALWAYS keeping the axles at the same speed unless there's enough torque difference between them to overcome the clutch friction. Only a POS Grenade-Lok requires RPM.

ramicio

iTrader: (-1)

I think you're talking about a helical LSD. The LSDs in these cars are of the cone clutch type. I see other Posi LSDs are cam and plate clutch type. No worm gears.

Straight from the factory service manual:

sofakingdom

iTrader: (1)

No, I'm talking about the thing you referred to in this quote, which is the Eaton Gov-Lock. It uses a system of springs and weights to "lock up" the differential when a certain difference in RPM between the axle shafts (about 150 RPM) occurs. It's found mostly in Chevy trucks; full-size as well as S ones. Here's what it looks like.



The assembly drawing you posted is a Borg-Warner 9-bolt, which was in fact used in many of these cars (but FAR FROM all); it uses clutches (#2) which require no RPM to "lock up", but rather, makes it relatively difficult (about 50 - 75 ft-lbs difficult) to turn one axle when the other is held still. No helical gears in that design.

The Auburn posi, which was used in most of the others of these that came with posi, is also a clutch type; but the clutches are of a different design from the cone style ones in the 9-bolt. No helical gears in that one either. Here's what that one looks like, in both 2 and 3 series.



Ones that use a worm or helical gear system include the True-trac (not OEM AFAIK) and the Zexel Torsen, such as was used in the later 4th gen F cars.

ramicio

iTrader: (-1)

I was thinking about it not in neutral. I guess in the friction of the clutches is enough to spin the driveshaft.