LSD ? help!
01-31-2002, 05:59 PM
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LSD ? help!
recently bought a 1987 951 and decided to change the trans fluid.i was told if i jack it up and turn the wheel if one turns in the opp- direction it is and open diff so i did and that is what it did.but when i put the car on the road and drop the clutch at 4000rpm it smokes both tires and leaves a nice black patch on both sides as it fish tails down the street.thus my confusion i also checked the option codes no 220 listed any thoughts?
01-31-2002, 06:17 PM
#2
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What a normal open-diff does is splits torque 50/50 in a straight line. As soon as one tire looses traction, though, it will get all of the torque, thus the fishtailing you get.
A limited slip diff. in the drag-racing start you did, will lay down two even tire marks and won't fishtai. Meaning your car will be aimed straight ahead and you won't need to dial in any steering corrections at all.
A limited slip diff. in the drag-racing start you did, will lay down two even tire marks and won't fishtai. Meaning your car will be aimed straight ahead and you won't need to dial in any steering corrections at all.
01-31-2002, 08:38 PM
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Why thank you Luke.
Another way to test the differential action (both open & limited-slip) is to find a nice tight corner, or say... 25-35mph. Fly through it on the inside curve and slowly crank in full throttle on the exit (unwind steering to compensate).
Do you hear the inside rear tire spinning & screeching, yet you're not accelerating very quickly? Then you have an open-diff or your friction-plate diff. is worn-out.
What is happening is that the weight-transfer under cornering lightens up the inside tire, reducing its traction. The 50/50 torque-split then gets to a point where it reaches the traction limit of the inside (lighter) tire and spins it. At this point, the inside tire gets 100% of the torque, and the outside 0%.
This is an easier test to perform than the straight-line drag-racing start. Even easier than raising both back wheels and spinning a tire. While that test may indicate the presence of a friction-plate diff., it doesn't show you its condition. If it's worn out, both tires will still move in the same direction, but during the cornering test, you'll find that the inside tire will still spin uncontrollably.
Another way to test the differential action (both open & limited-slip) is to find a nice tight corner, or say... 25-35mph. Fly through it on the inside curve and slowly crank in full throttle on the exit (unwind steering to compensate).
Do you hear the inside rear tire spinning & screeching, yet you're not accelerating very quickly? Then you have an open-diff or your friction-plate diff. is worn-out.
What is happening is that the weight-transfer under cornering lightens up the inside tire, reducing its traction. The 50/50 torque-split then gets to a point where it reaches the traction limit of the inside (lighter) tire and spins it. At this point, the inside tire gets 100% of the torque, and the outside 0%.
This is an easier test to perform than the straight-line drag-racing start. Even easier than raising both back wheels and spinning a tire. While that test may indicate the presence of a friction-plate diff., it doesn't show you its condition. If it's worn out, both tires will still move in the same direction, but during the cornering test, you'll find that the inside tire will still spin uncontrollably.
02-01-2002, 05:50 PM
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danno thanks but the open diff should be called a limmited slip because its truely not open and the limmited slip should be called a positrak dont you think?
02-01-2002, 10:38 PM
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??? there are open dif's and limited slip dif's but an open -limited- dif. do not exists.
a Limited slip dif just limit the slip. It is simple.
Konstantin
a Limited slip dif just limit the slip. It is simple.
Konstantin
02-02-2002, 05:01 AM
#7
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What about Torsen-1, Torsen-2, Torsen with spring-preload friction, etc.? Or viscous-coupled? Then there's friction-plate passive, friction-plate reactive, friction-plate computer-controlled, friction-plate rear-steer, etc... I guess all off these can be considered "limited slip" since they prevent the inside tire from taking all the torque and spinning.
P.S. PosiTraction is GM or Ford's trademark name for a friction-plate limited-slip diff.
P.S. PosiTraction is GM or Ford's trademark name for a friction-plate limited-slip diff.
