2wd with 3.55LS, 4.6 auto. Did some ls searches before posting with limited help.

OK, so I got stuck on a rutted icy drive way today, no biggie it’s ice right. Well here is the thing, only the right side is spinning. After adding a bit of traction sand to the right side tire the left tire did bite.

This whole thing tells me I need new clutches in the diff.

What diagnostics can I run to prove or disprove this. I will jack up the rear end later and with the truck in park try to spin one or the other tire (with the opposite in the ground).

I have never had to deal with bad posi clutches before as I have had Detroit Lockers in the past.

Any help appreciated.

Thanks Much
Jeff

 

OK, had each side up in the air and can turn neither side by hand with the other on the ground. Does that indicate good clutches? Seems to me not so much, because I can not produce the torque an engine does.

Jeff

 

How many miles ago was the fluid changed?

That might be the problem.....

 

Not sure, been at least 25000, probably more though.

 

Friction modifier added at that time?

 

Done at dealership

 

Your clutches could be bad but a limited slip is not a locker and with only one side on ice they are known to slip. A light touch on the brakes will even up the friction and should allow the other side to grab.

 

Truck has 125k and the clutches have never been replaced (that I am aware of). The fluid has about 30K since last change.

I now think the way to go is:
1st change out fluid and add less than full dose of friction modifier. Verify results.
2nd, and the more correct, order new clutches and just do the work. Have seen some vids and different stacking orders, should’t be to tough.

Problem is that I am soon moving and will be losing my garage space. Tools will be going to my daughters garage. There is space to work over there but I am not sure I wish to tie up her space for the 8 hours this is likely to take.

Jeff

 

Id be interested to hear about the results for your truck!!!! I have the same setup on my truck. Mine had a pinion seal leak. I just wasnt aware it leaked down so low. One day i am driving to work truck starts acting funny. Realized after two days that the fluid had gotten to low. Added fluid to it,, along with pinion seal fix,, the rear hasnt had any problems. But like you i have to wonder about my LS in the axel,,, weather the clutches need to be replaced. For that matter how the gears are doing!!!!!!!

HOPE TO HEAR SOMETHING

marc

 

LSD is not a locker. it will add power to the side that is slipping. It sounds like it is working correctly.

 

Same issue on mine. Had a ford Trak-Lok LSD installed at 30k and its never been worth the money really. Should have gone with the Detroit TrueTrac. Those don't have clutches that can wear out, and they perform better than the OEM LSD.

 

I haven’t done anything with it yet. I will replace the clutches in the spring. Machine has near 130k on it. Mine since 70k. Other than service, nothing else done to the rear end.

When I do the job I intend on going the Ford Motorsport rout with the best they offer. That should hold it for another 100k.

Jeff

 

Id seriously consider a truetrac. Wont wear out like the ford one will and it offers better performance.

 

I have a 2002 F150 2 wheel drive 5.4, owned since new. It has 220K on it now and LSD works fine. I changed fluids and added the Posi fluid at around 125K as the rear dif cover was rusted.
I never mis-used the truck though, so not a lot of hard time on LSD clutches.
Unless you are racing a lot or working the posi a lot, I would think just ad the posi fluid available at any auto parts store. Certainly the easiest and cheapest way out and the first thing I would do. Only about $8 for additive.
All you need is a rachet for the dif' plug and a narrow funnel or a syringe to put the fluid in with. Hope this simple fix works.

 

^^^