Dr.Kayak

I need some advice -- I have a 2001 4x4 with the limited-slip rear differential. It is not slipping as it should went turning under power. I am getting some rear wheel hop and can hear it binding. If you coast thru a turn it is OK.

130k miles on truck Royal Purple 75w90 gear oil and MagHiTech cover. Oil has been changed 3 times over the life of the truck. Oil lever is good, no excessive metal on the magnetic dip stick. No 4x4 thru deep water.

Any hope that changing the oil will help? $75 worth of oil if it's going to need a rebuild anyway.


Thanks for any advice.

Midnite

That's the limited slip unit working as designed. You can add limited slip additive if you want it to slip a little more.

Dr.Kayak

Thanks, but this is very extreme not sliping to the point the back end bounce off the ground. Never did this before a few weeks ago.

Guess I can change the fluid, $120 for that much Royal Purple. It has been in there for several years.

SIXSLUG

Fresh fluid isn't going to cure a mechanical problem.

I'd drop the cover and inspect the carrier and bearings and also check the bottom of the housing for debris and parts of bearings etc.

You can thoroughly clean the housing and catch the fluid in a clean container and reuse it possibly, but I'd go with new stuff.

nickg

add some more slip additive first, its like 6=7 dollars, if you drop the cover inspect every thing before throwing expensive oil in there. when mine had no additive it was an aweful shudder when cornering or backing up

heres what my limited slip looked like, it made no hopping/bucking, just acted like a one wheel peeler
cost about 100 to replace the disc and steels

plow

Trans-X® Posi-Trac® Limited Slip Gear Oil Additive by K & W Chemical - part# 402508
This is what I use in mine.

torquefan

It probably would benefit from a fluid change, but I would also try adding a bottle of friction modifier first, and drive it for a week or two, then you'll know whether to just change the fluid, or to overhaul the limited-slip unit at the same time.

SIXSLUG

When did you last change the diff fluid? I am under the notion that this problem just started and the last oil change was a while ago.

If the change was very recent add the modifier, if not see my earlier post.

Dr.Kayak

The issue had got worse over time. For months I though it was the front U joints binding. Only after it got so bad I could see the bed bounce when backing in a tight turn, did I get a clue it was the rear having a issue.

Friday I replaced the oil in the diff. It had been in there for 80,000 miles. Royal Purple has the friction modifier in it and has worked fine in my truck in the past.

The new Royal Purple made a big difference. I had a clunk putting it into drive that is gone. The wheel hop on tight turns is mostly gone. I am thinking about adding aditional friction modifier to see if it will slip more.

Thanks for the replies, guess I been letting the truck maintenance go as I have been motorcycle crazy for the last 3 years.

KATOOM

I agree with SIXSLUG. If its as bad as you claim then there's probably an issue. I dont care if you never use friction modifier, the OEM limited slip should never be so tight that you have wheel hope. Chatter when the differential gets warm.....yes.....but grabbing and hoping tires.....no. Especially since the hot weather is over. The Mag Hytec has a drain plug so drain the lube, save it, inspect the carrier for issues, then reuse the lube if all checks out. Dont try to cover something up by adding more stuff.