zachhansman89

ok ive looked and looked on this forum and can't seem to find anybody with my problem with the 4x4 my truck is a 04 lariat4x4 and works and runs perfect but recently i took my truck down a few trails and engaged the 4x4 when i did this it engaged as usual and when driving in a straight line works fine but as soon as i start to turn with the 4x4 engaged the rear tires begin to skip one will almost lock up or the other will spin faster than the otherwhile i turn almost like locking my differential? before when i put in 4x4 and turned on the street or in grass or whatever they would both turn normaly aka'' one would turn slower than the other so that way the wheels wont skip'' well now as i said they both wanna almost turn at the same speed it seems and then it locks up one tire and causes the other to burn out ? anybody out their who knows whats up?

driver444

I don't think you have a problem at all. If your 4x4 is engaging, IT WORKS! But here's what I think is going on...

As you know, when you make a turn, your inside wheel turns slower than the outside wheel. And that is true for the front axle also. But here's the thing. When you make a turn in 4wd, not only are your inside and outside tires spinning at different speeds, but there is also a difference in speed between your front and rear axles. The front wheels travel farther than the rear when turning. So basically, you have 4 wheels that want to turn at 4 different speeds, and while the left and right tires can turn at different speeds thanks to the differentials, the front and rear axles are LOCKED together via the transfer case, and FORCED to turn at the same speed. Something's gotta give way, and that's what you're feeling.

This is totally normal. And the skipping you feel can be more pronounced when you have a limited slip differential.

zachhansman89

yeah thats exactly what i figured my only problem with that is its never done that before the differential allowed it to turn enough that it wouldn't skip now it does? now when i turn i realy have to gas it as well or else it wont even move cuz the inside tire wants to stay in place while the outside spins i guess for a straight line having your differentials locked in place would be a bonus but ya gotta turn eventually! every now and again it will give me a problem going straight but thats rare its usually when i turn?

driver444

You gotta look at it this way... Your front differential is "open" so that's not causing the condition you describe.

The culprit would have to be the rear differential. If the rear differential was "locked", it would make a tire drag even in 2 wheel drive. If the truck handles and operates properly in 2wd, there's no problem, since engaging 4x4 has no effect on the rear differential.

I can tell you that if you put ANY 4wd vehicle (in 4wd) on dry pavement and turn the steering wheel all the way in either direction, it won't roll without some serious pressure on the GO pedal.

I don't think you have a problem at all, except MAYBE, (and I doubt this would make a really noticeable difference) if you have a limited slip rear end, you could change the fluid and add the friction modifier. The clutches in there might not be slipping smoothly.

nashtruck

Owners manual states not to engage 4X4 on dry paved surfaces.

driver444

Yes it does, and this is exactly why. On slippery surfaces, wheels can slip, and on dry pavement, parts wear and break instead.

nashtruck

Excactly my point, the op said he was in 4X4 on the street making turns... not good

zachhansman89

it also does it tho when im in soft terrain as well aka dirt mudd grass i guess i could be wrong both my buddies jeep and grandfathers ridgeline dont do this if its common with ford then i guess ya learn something everyday! now heres another question for you i have 80k on my truck now ive never changed the diff fluid how often and what type of fluid should i use ? and anything i should do while im at it to save me in the long run? suggestions?

driver444

With our year trucks, the manual says that you NEVER have to change the rear fluid unless the axle's been submerged in water, or has been disassembled for service. Just check it periodically, and add to it.

Even though I'm no engineer, I disagree. It never hurts to change fluids more frequently. I'd say every 50,000 on a rear end is good, especially if you tow alot, (but I'm a little fussier than most).

If you bought the truck used, and don't know it's history, I'd change the fluid YESTERDAY, but if you got it new, and you never crossed a river with it, you're probably OK. I think I'd change it soon though for peace of mind.

Our trucks call for synthetic axle lube. Many people (myself included) use Royal Purple for the rear ends because in the event you have a limited slip differential, (which you probably do) it already has the friction modifier additive in it. And if you have an open differential, it won't hurt anything to have that additive in there.

Other than that, rear ends are pretty much maintenance free. You pretty much wait until something leaks, makes noise, or breaks to worry about it.