Maybe someone here has had similar problems. I have searched thru the posts but haven't found anything quite the same as what I have.

1st of all, 2000 Expy, 108k miles, 4.6L 4x4.

At about 60k, it started to have an instantaneous slip in OD under acceleration less than what would downshift out of lock-up or into 3rd. It would feel like it was taken out of gear for a fraction of a second and then put back in.

This stayed the same for a while. I had the trans fluid flushed at about 78k, before a long (5k mi) trip out west. No discernable problems on this trip other than what was already going on.

Recently it has deteriorated dramatically. Lack of power, shudder in all gears, hard downshifts (very noticable when coming to a stop), similar "slips" in all gears but much more pronounced, grinding sounds. Sometimes it feels the same as when the AWD kicks in when the rear wheels slip.

Had plugs changed at about 103k at the suggestion of a trans shop that the problem was because of a miss. The power was better, but nothing else.

Took it to Ford dealer and they could not identify any problems. They also suggested another plug change because "these engines don't like plugs other than Motorcraft"

Had trans fluid flushed again but no change. I know everyone here is going to cringe, but I had it done at Instant Oil Change, and they put in MaxLife ATF (both times)

If I had a miss that was this bad wouldn't an engine code be thrown? I am going to change the plugs again, fuel filter, and check all coil packs, but I don't think that will solve the problems.

Has anyone seen anything like this, and what was the solution?

Thanks in advance

 

First question is does your trans require Mercon V and if so, is that what you had put in?
Sounds like shudder to me. Nothing to do with the engine. You may need trans work now. It's never going to get better from what is done from the outside.
Good luck.

 

Finally figured this out, and I thought I'd post as an FYI for those of you who have Expy's or pickups with AWD.

Not long after I posted this, I replaced the tires on the rear of my Expy with new and put the old rears on the front. I had the tires in my car at work. A co-worker asked about them and also mentioned that I should be careful when replacing only 2 tires on a 4WD vehicle. The old rears had about 40k on them, and the former fronts had about 60-70K (worn out).

As soon as I had this done, all of the problems I outlined went away.

Apparently the AWD system doesn't like tires with different diameters due to wear. I would have assumed that the system would engage 4WD when the rears were spinning faster than the fronts, but it didn't like the fronts spinning faster than the rears either.

 

all fingers are pointing to the torque converter. mine was doing a little of the same thing (altough not nearly as bad) and its up in the air getting a new torque converter, jasper tranny, rear diff service, new u-joints on the drive shaft, and a new tranny cross member. its a 2000 f150 with a 5.4 and only 91k miles, meticulously maintained. the fluid i the tranny was only a year old, and was still totaly clear, but once we got it out we could see that the torque converter was slipping a lot (this is what your experiencing). also, the pump in the tranny was shot. all in all, its going to be at least $3300. probably more. you might want to get on it though.