I have a 99, 5.4L and it seems to be slipping when starting off. It is a very slight slip (seems to only be in first gear) and only does it when I really get on the gas from a stop or I'm starting up a grade from a stop or slow speed. Also, the engine doesn't rev up when it slips. It has the tow package with the E4OD/4R100 transmission and the 3.73 limited slip rearend and about 85k miles. I serviced the transmission about 4k miles ago (drained pan and torque converter, dropped pan and replaced trans filter, and refilled with mobil 1 syn).

Does this sound like a transmission problem? I looked through the service records and saw where the previous owner took it to the Ford dealer complaining about a slip and a noisy rear end (@ 54k miles). Dealer drained rear diff and refilled and added friction modifier. Could this be the problem again?

I do use the expy to tow a camper (~4500 lbs) 3 or 4 times a year. In fact, I have a trip planned for late July and need to get this slip figured out. I don't want to drop a transmission towing a trailer up a steep grade!!

thanks,
philip

 

Since the engine RPMS don't rise when it "slips", I'll need a definition of "slip".

Whenever I had a transmission slip the revs would rise but not the forward speed of the vehicle.

Could you go into a bit more detail as to what you mean by "slip", please?

 

definition of "slip".

About the only way I can describe it is the truck is accelerating hard and then stumbles momentarily.The rpms don't jump during this stumble and the truck catches again and starts accelerating. It would almost be as if I had a manual transmission and pushed the clutch in very briefly with the exception the rpms don't jump.

It's somewhat similar to a problem I had in a car once. It would "stumbe" when accelerating hard and it turned out one of the plug wires was breaking down. I've wondered if I could have a COP that was intermittently going cutting out. The plugs were changed about 10k miles ago and the #4 COP was replaced (back, passenger side).

thanks in advance,
philip

 

Uhhhhh....

Which one?

 

I would call that a "miss" and would look at the COPs and even the fuel filter before I suspected the tranny.

 

I thought I'd post the resolution to my problem and maybe someone can benefit from it (save some money).

I finally took the truck to the dealer and had one of the technicians go for a ride with me. As soon as I pulled out of the dealership and got on the gas, the truck slipped and the tech immediately told me it was my transfer case. The way he explained it (I may not have it exactly right) was that the transfer case has a clutch(es). Under normal operation, these clutches engage when the rear tires begin to slip (automatic 4WD) and transfer power to the front wheels. With my truck under a heavy load (accelerating hard or going hard up a hill), these clutches were sticking momentarily (kinda makes the truck shudder, or in my case, I thought of it as a slip).

The fix was to service the transfer case (drain and refill with ATF) and the rear diff. (drain and refill with synthetic and friction modifier). Also, they reprogammed the processor. I have no clue what this is (I looked in Haynes and my Service manual). I asked the service manager and all she said was that any time they work on the rear end it requires a reprogram. Anybody know what this might be?????

The cost:

Labor 135
oil (rear diff) 53
friction mod. 15
ATF 8

enviromental fee 10 (?????)

total 240 (ouch)


I thought about servicing the front and rear diffs and the transfer case myself, but I wasn't sure if that would take care of the problem. Next time I'll take the time and do it and maybe save some money.

 

Thanks for the feedback Philip. It's good to know that your problem wasn't "major." Yeah, you could have done the work and saved $150, but sometimes it's worth the added cost for the peace of mind.

 

You can also solve this problem by pulling the fuse for A4wd, of course then you lose 4wd options...