I have a 2007 ford f150 fx4. 373 gears, limited slip differential. Today i was pulling a work van up a driveway that was snowy, because the van was stuck. While pulling the van i noticed while in 4x4 high, that all 4 wheels on my truck didnt spin. I put in 4x4 low, and all the wheels didn't spin. Are the wheels all supposed to lock in and spin ? Since they did not, do i have an issue? The right rear, and the left front spun in the snow. I drive in 4x4 all the time, and haven't noticed an obvious issue ?

 

That's normal, but your rear LSD may be shot. Both rear wheels should spin, but the front wheel with the least traction will spin, the front diff is an open diff, not limited slip.

 

wjat does that mean exactly? There is no noise, and everything seems ok? What is a plan of action?

 

It means, the clutch packs may be toast - requiring a rebuild and fluid change.

 

Sounds expensive. The truck has only 76k miles

 

When in 2 wheel, the right rear spins, and the left does nothing.

 

Yep - bad sign - LSD diff should be transferring torque. 2wd or 4wd does not matter - rear diff does not know what drive system is in use.

The front is normal - it's a simple open diff.

I'd start by changing the fluid and seeing what comes out - need to pop the cover to inspect innards anyway. Don't fergit the 4oz of MC XL-3 FM (friction modifier). LSD's need changes every 30K or so anyway due to hydrophyllic FM ( bless good ol' Labnerd fer that gem, lol).

Good luck
MGD

 

Thanks for the help. Should i have the dealer do thos, or is it simple enough to tackle on my own?

 

Very simple to do. Metric socket set, oil pan and silicone is all you need. And some brake cleaner to wash out the inside. Also, oem LS are less than stellar in performance anyways.

Get 3-4 quarts of 75w-140 synthetic gear oil. I use royal purple as it had the friction modifier in it already.

 

Thanks for the advice. Fluid change took care of it!