nick1

1985 gsl. so i lifted the rear end, and turned one wheel, and the other turned in the same direction. that confirms i have lsd right?

i had a friend hold one of the wheels, and tried to turn the other one, and to my surprise, it DID turn. not easily, but didn't take TOO much force either. is that normal, or is my lsd worn out?

nick

steve84GS TII

Depends on the age,but yes you can turn one wheel while the other is held still.Mine was very worn out and wouldnt turn the opposite wheel in any direction when I turned one by hand.But it still hooked up when I floored it,since the LSD grabs harder the more power you feed it.When theres no power,theres very little grab.

nick1

oh i had no idea it "grabs" when there's power. cool that makes sense. thanks!

Mr BiG G

it has a clutch type thing in it that helps it grab when theres more pawa(power)

superslydr

think about this for a sec and you'll be as confused as me.....when i turn the passenger side wheel my driver side turns the same way....when i turn the driver wheel the passenger turns the opposite way....but it almost always leaves 2 black marks......what kinda goofy rear end is this?????

Moonchopper

Are you sure those 2 black marks aren't from one wheel going forward and the other spinning backwards?

superslydr

lol good one.......well if the car sit in one place without any braking i might would start to think that

steve84GS TII

If you have equal traction at both tires,any rearend will leave 2 marks.Its all about resistance.With equal resistance there is no differential action and both tires get equal power,like you have a spool.But very few situations leave both tires spinning exactly the same number of times and under the same load.
The clutch LSD uses input torque to press the clutch plates togther tighter.More torque,more grab.The springs apply a little preload pressure when theres no input,but its easy enough to overcome those springs when the wheels are in the air.Its even easier when the clutches are worn/old.

nick1

so how easy (or hard) should it be to turn one wheel when the other is being held (or on the ground) with lsd?

with my car, it wasn't easy, but i didn't have to use all my strength either.

jays83gsl

Well, I barely have to turn my LSD with one wheel on the ground, and the air wheel turns.
My LSD is so fried. I'm sure of it. It's always wet, too, for some reason

nick1

i don't get it though. doesn't make sense to me. if one wheel is on the ground how do you turn it?

or do you mean that WHEN one wheel is on the ground the OTHER one turns easily

GavinJuice

so if accelerate from a complete stop and i feel a clunk right before the wheels rotate that would be also a bad indication of a bunk LSD? if i rotate the driveshaft by hand i have some play before the wheels kick in. And no i don't have bad u-joints.

steve84GS TII

The differential allows any amount of power distribution between the 2 tires.Anywhere from 50/50 to 0/100.If you hold one tire still(or leave it on the ground) and turn the other tire,your just turning the diff. gears inside the carrier.They are walking around the spider gears,allowing the one wheel to turn,while the driveshaft and opposite wheel remain stationary.
The LSD loosely connects the 2 axles together via friction generated by the clutch plates/springs.They can still spin independantly to provide differential action while driving,but when torque is applied to the carrier,the LSD blocks expand under the load of the centerpin and push the clutch plates together,trying to lock the 2 axles together.The more power and friction is fed to the LSD,the more the two axles will act as one.You should be able to turn one tire with a mild bit of effort.Not free spinning,but also not feeling like the brakes are one.Thats an average,healthy LSD.
A full locker, like many truck and jeeps have, will temporarily "lock" the two axles together when under load.You then have full power to both tires,no matter what.Its great for traction in mud,sand and rocks,but can be harsh and jerky on the streets where the tires cant slip when they need to turn independantly.The LSD gives you a percentage of the full locker's capability but with far less uncomfortable pops and jerks.
The slack in your rearend can be several things.If its the ring and pinion you should know it cause the rearend will usually be howling and whining badly when the R&P gears get really worn.It can also be the side/spider gears in the main carrier where the LSD plates are.They tend to wear faster than the R&P since they are smaller,but have to transmit all the power to the axles.The LSD plates can be good, even if the gears they work upon are worn.Either way,you have to open the whole thing up to fix it,so might as well replace it all while its apart.Could also be a snapped axle clunking around.Unlike drum rears,disc brake axles cant flyout as easily if the axle shaft breaks inside the differential.

nick1

steve sure knows his rear ends!!!

GavinJuice

Well my only thoughts on what could be the problem was too much play between the ring and pinion. I'm not sure what else would be moving before those 2 parts. Now i have 2 used LSD units i picked up dirt cheap that both have no play which is good. I'm gonna check the FSM for proper play. I guess i won't know till i pull it out and take a looksie on where this play is. But its too cold in MN right now so thats a later project.

steve84GS TII

If the driveline yoke turns but the wheels dont turn right away,its almost impossible to tell which part is worn unless you pull the 3rd member out.My old Jeep Dana 35 had huge amounts of driveline lash,like almost a quarter turn before the wheels would move.The ring and pinion lash was perfect(1/4 turn would be impossible unless the diff teeth were stripped off!) it turned out my Detroit locker(equivelant to the spider gears) was very badly worn and was the cause of the slack.Turning the driveline,youd think it was the main gears,but in actuallity it was the internal working of the differential that were worn.

I did recently replace my RX's rearend,but I learned the vast majority of my driveline stuff on the trails.Being heavily into rock crawling for 10 years,you see a LOT of carnage in the trans/driveline/axle departments!

Moonchopper

lol, I understand the carnage part, steve. Although I'm not into rock crawling as much as you (or was), I definitely have had my fun off-roading (by off-road, I mean on rocks, not just mud bogging). It wasn't with any of my friends, but with other people who have been off-roading and are into it hardcore.

You wouldn't happen to know anyone named Bruce Hatton, would you? Definitely a long shot, I know.

I recently replaced my '82 open diff with an '83 GSL LSD, and I can tell you, it's not hard at all. I don't know what you'll need to do exactly, but I had to pull the parking brake cables (those were the hardest part, since the fawking heat shield and some kind of crossmember/skidplate for the fuel components were in the way) since I converted from drum to disc brakes. Oh yea, I accidently put the wrong brake cables on the wrong sides. Man that pissed me off so much. If you have to swap the cables, MAKE SURE you know which cable goes on which side. One is shorter than the other.