so its weird some times when i am practicing my launches (empty stretch of road by my house) for reaction time, i sit there pull into my water box and go to burn them and sometimes i get both wheels going, sometimes peg legs the right one,

so my question is why does this happen ??

when i got the rear i changed the fuild to Mobil-1 75W-90 full syn with a bottle of MOPAR suregrip additive ( got a whole case from when i was working at a chrysler dealer few years back), drove in a figure 8 to allow full splash on the gears

its a 2.94 suregrip out of a '78 lebaron (in my '79 volare),

-Mike

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I am the Guardian, I hate helos, everything leaks.......

Many synthetic lubes do not need the friction modifier. For one reason or another the clutches can't handle the load. It could be too slippery a lubricant or the Sure-Grip could be worn out. Is this an 8 1/4?

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Joshua

yes sir shes an 8 1/4, should i drain and fill with the regular 75w-90 and just use the additive ??

-Mike

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I am the Guardian, I hate helos, everything leaks.......

All clutch-style and Torsen-style limited slip differentials have to have the clutches preloaded in order to engage and hold. This is done by simply stepping on the brake while applying throttle.

If you are starting on a surface other than wet ice, and the differential is the Auburn design (5 coil springs in the center), then the differential is nearly worn out. When this happens the clutch cones wear to the point that the oil channels are gone and the cone is bottomed in the case. With no oil channels, the cone will ride on a film of oil and not grab. If its the older (pre-'92?) split case design, its sometimes possible to machine the small face of the cone ~0.020" and shim the differential gears to restore limited slip functionality for a while. You can hand-file the oil channels to make them deeper. If its the newer end plug housing, its not repairable.

The Torsen (all gear) limited slip has no preload of its own. With one wheel on ice, it will behave like an open differential until preload is applied with the brake.

The disc clutch style units (TracLok, etc) use Belleville springs in the clutch pack to apply some preload. If the clutches are worn (very rare), they will slip until preloaded with the brake. The clutch packs can be replaced. A special tool is required to compress the clutch packs so the pinion gears can be rotated into the case.

Ken

The additive is to reduce clutch chatter by allowing more slippage. If you want more lock-up try conventional gear oil with no additive and see how she behaves. If it still spins one wheel it's likely worn out.

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Joshua

The FSM method of testing a limit slip is to lift the wheels off the ground with the transmission in PARK. Turn one wheel until the other side turns in the opposite direction. If it requires more than 35 lb-ft of torque, the limited slip is working.

Ken

Ken i will jack her up tomorrow and test her out, and i always preload the tires via power brake/linelock

josh i will try just the conventional stuff this weekend to see if she improves any

-Mike

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I am the Guardian, I hate helos, everything leaks.......

just out of curiousity is there any difference between 80W-90 and 75w-90 ?? other than the initial viscosity weight ??would one be better than the other ????

-Mike

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I am the Guardian, I hate helos, everything leaks.......

The only difference is the cold viscosity. The hot viscosity is identical. You can use either one.

Ken

Synthetics all seems to be rated at 75W90 whereas the convention lubes seem to be rated at 80W90.
at least this has been my observation over the past while.

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1969-1/2 Dodge Super Bee A12 (440 Six Pack, 4-spd, Dana 60)
1974 Plymouth Duster 360 (4-spd, 8.75")
1973 Plymouth Duster (225, auto, 8.25")
2001 Dodge Ram 1500 QC 2wd (5.9L, auto, Dana 60)