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I was backing my 02 Super Duty 4X4 up a hill in the wet grass to hook up to my trailer when the right rear wheel started spinning. I had the truck in 4 low and I think I may have a vacuum leak to the front hubs that was keeping the front wheels from pushing me on up the hill, but I felt the back tire should not have spun unless maybe the limited slip rear ends in these trucks are not designed to function in reverse? The truck just sat there spinning the right rear wheel and would not go anywhere. Does anybody have any first hand knowledge of what should have happened in this situation if everything had been working properly since I'm not that knowledgeable on 4 wheel drive/limited slip?
Yes, the limited slip should have worked whether going forward or reverse, it doesn't matter.
You probably have the usual problem with the factory limited slip, the clutches are worn too much for it to operate correctly. The factory limited slip wears out very fast, mine only lasted 1-2 years working correctly.
If you are in that situation again, try holding one foot on the brake giving it light pressure while accelerating at the same time, this sometimes helps to load the limited slip and makes it work a little better.
the brake trick works like a champ most times...I prefer to use the e-brake when doing that. engage the e-brake 1-3 clicks. you'll get the annoying chime/light of course
but yeah, the LS should work fwd or backward. heavy truck = wears out quickly
I'm assuming the front wasn't working properly either? Even if the rear wasn't working properly, if the front was I still should have had 3 of the 4 wheels pulling....right?
I'm assuming the front wasn't working properly either? Even if the rear wasn't working properly, if the front was I still should have had 3 of the 4 wheels pulling....right?
I'm starting to wonder if there trucks are even legally permitted to be called 4x4.
My understanding(I am not a mechanic):
Front is always open diff. Rear was sometimes locking or LS on previous models; I think they are limited slip on 2011+.
So basically when everything works you get at most 2x4 if one of the front wheels slip or 3x4 if one of the back wheel slips. Now imagine that the limited slip is not working you could be stranded with just one front and one back wheel slipping.
Maybe there are some ABS magic at work to stop some wheels from slipping; other manufacturers do that. Never read about it from Ford's pickup.
Maybe there are some ABS magic at work to stop some wheels from slipping; other manufacturers do that. Never read about it from Ford's pickup.
the new F-150's do that. they get a elocker for the rear axle. the ABS is used to provide LS type traction when not locked, or for axles without the locker installed
not sure if this has made it's way to the Superduty line-up yet though
I'm starting to wonder if there trucks are even legally permitted to be called 4x4.
My understanding(I am not a mechanic):
Front is always open diff. Rear was sometimes locking or LS on previous models; I think they are limited slip on 2011+.
So basically when everything works you get at most 2x4 if one of the front wheels slip or 3x4 if one of the back wheel slips. Now imagine that the limited slip is not working you could be stranded with just one front and one back wheel slipping.
That's incorrect; all four wheels are applied the exact same torque all the time. The problem with an open differential is that the maximum torque available to one wheel is equal to that of the other. So when one breaks free it's because of low traction, which limits the torque applied to the wheel...which in turn reduces the available torque to the other wheel in the same amount.
They are truly 4WD, but the tractive force of both wheels on an axle will almost always be exactly the same. That one wheel on ice is providing the same amount of motivation that the other wheel is on dry pavement. But they both have power.
I've had 3 or 4 SRW limited slip rear ends in Ford trucks and they didn't really work in forward or reverse very well but I'm on my second DRW with Dana 80 limited slip and they work very well in both directions even after 130K in my last one.
Thanks for all of the replies. I am really learning a lot about the rear axle on these trucks after reading these. The yard has dried out a little since my first attempt, so I'll try to get that trailer out again tomorrow. I will give the braking a try while pushing the accelerator trick you guys have suggested.
Another thing to look at is your choice of tires. The best LS or locking diff you can get is useless if you don't have the tires to put the power to the ground.