Checking for LSD

[jorgen]

i am buying an opel GT from GReensmurf on here... and he said he believes it has a LSD in it i was just wondering what i woudl have to do to check that out to make sure that it does or doesn/t like if i jack up the rear put it on stands... and spin one tire should the other side spin the same direction opposite direction or what?

[namba209]

Jorgen, with the ZF positraction in my GT, when I have both tires off the ground and spin one tire, the other rotates in the same direction. So I guess that's a quick and dirty way to check for a posi-traction rear end. HTH.

Ron

[jorgen]

thanx man that is what i thought but i have only ever worked with front wheel drive cars so i didn't know forsure how things worked with rear drive cars...

[greensmurf20]

if they're supposed to spin the same direction, it might not be a limited slip posi. you spin one tire and the other spins the other direction, but if you dump the clutch at 3500 it spun them both for about 50-75 feet, then dropped one wheel and just spun one for the rest of the way..........so maybe just a oddball single track?

[jorgen]

so from the kids description of what goes on while he drives it what do ya'll think does it have a LSD or should i be planning on adding that to my list of need to buys? when i start on the driveline

[namba209]

One other way to check out a non-posi is to hav both wheels off the ground and have a person hold one wheel, preferrably the left rear and spin the right rear by hand. If just the left rear turns and the right rear does not try to move, it is a non posi. If both try to turn it is a posi, regardless of which direction the other tire turns. I think, but don't quote me on that.

Jared, when you wind up the engine to 3500 and dump the clutch, both tires will break loose and drive until they get traction, then the driven wheel, single, ususally the left rear, will continue to drive while the other will tag along. JMTCW.

Ron

[nobody]

Posi is the only one that both wheels turn in the same direction. Because of the internal gears for a LS they turn in opposite directions. If you hold one wheel and spin the other the drive shaft should turn, if trans is in neutral. The only posi's I am aware of in the Opels have been added after the fact. Opels in that year range had LSD, it is just the problem of the gears only handleing up to 175 horse. If you plan on going past that and pushing it you need to think about a change. There are a load of threads on this subject.

[oldopelguy]

Positraction, or posi for short is GM's name for their factory limited slip differential.
Chrysler called it Tru-track or Sure-Grip, and Ford had some other name I'm sure.

Limited slip rear-ends used by most manufacturers have clutches that wear out over time. When they wear, the axle effectivly turns back into an "open" rear end. Combine that with the Opel's tendancy to have axle oil vanish into the ether, and you are almost guarenteed that any origional LSD is going to be worn out.

The good news is that the LSD can usually be rebuilt, the bad news is that the only real way to tell if you have one is to pull the cover and look at the actual spider gears for clutches.

A locking differential locks the 2 axles together and was never an option.

[GTJIM]

1) Position the car with one rear wheel on the pavement and the other in the gravel then do a spirited takeoff. If the wheel in the gravel spins madly then it is not a limited slip. If it drives and does not spin too much then there is posssibly a LSD unit in there.

2) Put the diff up on jack stands and rotate one wheel by hand with the car in gear. If the other wheel turns backwards then there is no working limited slip unit inside. If the other wheel does not turn when the car is in gear but turns in the same direction when out of gear then there is certainly a limited slip unit in there. Especially if you cannot turn them in different directions by hand

3) Take the rear cover off the diff and have a look inside. A non-slip diff has ONLY side gears and spider gears inside the differential cage. A LSD unit will have several clutches behind the side gears(positraction type) or lots of little spiral gears between the side gears(Quaffie/Torsen type) or funny things with square teeth on them (Detroit locker). A posi or a torsen type are most likely in an Opel diff. Isuzu Impulse ones are "posi" type and Quaffies are "torsen" type. Never heard of a "locker type for Opel diffs as they mostly come in 9" Ford diffs.

[calvin]

I am almost sure that some of the 70,71, and 72 1.6 and 1.2 (1.1) ascona's and manta's had posi's rear end at least in germany. I had one ina a ascona ther. it wasn't good for much over 150 kM but would get fast.