First the details.
2007 FX2 crew cab
5.4 with 85,000 miles
100,000 powertrain warranty

A little over a year ago I had my computer reflashed for the transmission felt like it would slip when turning from a slow speed. Fixed the issue. About a week ago I noticed it seemed to being doing something similar again. It does it an any speed with partial throttle. Now it is starting to slip (or what feels like slipping) very bad at highway speeds when I give it a little throttle. If I get it to kick down, it will stop. It's not just limited to OD either. It has done it in drive and I think 2nd also. Anyone experience this? I plan on getting it to the dealer this week but just wondered if anyone else had experienced this.

 

Or could this be related to the limited slip diff?

 

Anyone?

 

Not the limited slip. Even if the clutches were worn slam out, it wouldn't slip .... it just wouldn't act like a limited slip .... it'ld be like an open rear.

When was the fluid last changed with fresh Mercon V and have you checked level?

Is it a hard working truck? Hard playing truck? Street ride?

 

Fluid level is fine. Has not been changed yet. That is the first thing I'm going to do before taking it to the dealer. It sees normal highway driving. 100 miles a day.

 

You do know that a pan drop will only get about 1/3 of the fluid out of the tranny - you may want to consider paying the dealer or a quick lube shop to do a full fluid exchange with a machine.

 

OK Now I'm a bit stumped. I have not been able to get the truck to the dealer yet due to work schedule. Plan is getting it there tomorrow. While driving home yesterday it did the same thing but would not stop the shuttering when I got it to kick down. However it almost acted like a coil was going bad and the motor was cutting out and lost some power. After a few seconds of feathering the throttle, it settled back to normal.

 

At 85k, it probably does need new spark plugs - which are NOT a warranty item. Coils are also a possibility, those may or may not be covered.

 

i was planning on doing the plugs soon. this may just speed up that process.

 

Ended up being a bad coil which I just took care or, but sure didnt act like a coil going bad.