Nismo3112

iTrader: (12)

Here's one thing I dont understand.....

If you test if your tranny has an LSD or not, by turning the wheel and watching the other wheel. If they spin the same direction, then how does an LSD car park say on a hill>?????? Is the tranny in gear when you turn the tire?

mhadford

I didn't test for LSD by turning one wheel, since that wouldn't work. I checked the transmission model code on the firewall.

The viscous limited slip works almost like an automatic transmission torque converter. There are vanes placed close together, swimmin' in fluid. At very low spin rates, or spin differentials, there is no torque transfer; just like an autotragic transmission doesn't do anything at idle.
When there is a big difference in spin rates, the fluid between the vanes will transfer some torque.

So if you turn a wheel by hand while car is jacked up, it will behave like an open diff. Opposite wheel will spin in opposite direction. Same for normal cornering. It will only transfer torque with rapid wheel spin, as when burning out or having one wheel on ice or in mud.

JClaw

iTrader: (17)

Sorry to wake up an old thread:

I know my car (1995 SE 5-speed Canadian spec) has an LSD. I did not check the number, but when we changed the seal the dealer had two choices: Normal or Posi Traction. First we chose normal. Didn't work. So we tried the seal for Posi Traction and it worked.

Yet, someone said "There is a way to test if the LSD is working. You jack up the car to where both front tires are off the ground and spin one tire. If the other tire spins the same direction it is working. If it spins the other direction or not at all then it is not."

What does that mean? Does it mean that it's broken or that there is simply no LSD? I know for sure that I have an LSD, but if it was broken, would I know it by doing that? I mean, the car runs great, no noises, great at taking curves but you never know....

If, by any badluck, my LSD is NOT working, will fixing the LSD be included in a future transmission rebuild.

Nismo3112

iTrader: (12)

This method still confuses me. IF the LSD were working and the tires did spin the same way........ How in the world would the car stay put when parked and in gear??

Broaner

iTrader: (10)

JClaw, if they go in the same direction you have LSD. If they go in oposite directions then you have an open diff. It could be that it is broken but unless the previous owner drove the car real hard the fluid would still be able to do its job.

Nismo, friction. Its not the counteraction of the tires that hold it still. Its the amount of advantage the tranny has over the engine when in a low gear.

Nismo3112

iTrader: (12)

I still do not understand... So you would be able to turn the wheel by hand (wheels going the same direction), but when parked say on a uphill street, the wheels are locked?

JClaw

iTrader: (17)

We're in the same boat, 'cause I don't understand your question.

Broaner: Hopefully my LSD does work. I mean I am 100% sure I have one, because only the Posi Traction seal did fit, but I am not 100% sure it works because honestly I really don't remember if both wheels turned in the same direction or the opposite. I will check next week when the car is on the lift.

But there are no leaks, no sounds, nothing unusual, car runs perfect. So hopefully that means my LSD does work.

If not, are LSD trannies more expensive to rebuild than normal ones? If so is there a big difference?

JClaw

iTrader: (17)

T t t ....

Broaner

iTrader: (10)

The diff is basically independant from the tranny. I don't know if they can be rebuilt. I've always carried the impression that the expanding fluid can lose its thermal expansion properties over time; causing the LSD not to work and actually perform as an open diff. My guess would be that a simple flush and refill of whatever fluid this is would return it to normal. Or maybe the clutches wear out. Really, all this is speculation.

Having the open diff does nothing to effect the tranny's ability to hold the car still due to friction. I really can't think of any other way to say it.