<hr style="color: rgb(209, 209, 225); background-color: rgb(209, 209, 225);" size="1"> <!-- / icon and title --> <!-- message --> Hello to all. I've looked through many posts on this site and found a lot of great info, but nothing exactly like my problem.

02 Mountaineer with 4.6, 5R55W trans, towing pkg. 100,000 miles on the odometer, purchased used at 80,000 so I do not know the service record on it. Diff has a slight leak from a point high on the diff, according to the shop, but has been topped up. Diff is quiet. I have not changed the trans fluid yet.

This happens especially when <input name="IL_MARKER" type="hidden">towing the horse trailer, 5000lbs, but also can happen at times not <input name="IL_MARKER" type="hidden">towing. OD will be off and while going up a grade, if you let off the gas just a bit, it will downshift 4th to 3rd, and you'd think you just hit something. The noise and jolt you get will wake you up and scare any passenger in the truck.

My thoughts are trans, after reading all the great stories about this 5R55W, but I would appreciate any thoughts. Thanks for any ideas and suggestions and I hope I have supplied enough info to work from.

One other note, No flashing OD light.

 

Go back and check the drive line for loose/tight universals and sticky slip joint.

 

Thanks for the reply. Crawled underneath and all looks and feels tight. Leak at the diff is at the right hand boot for the CV joint.

 

Feel tight is not good enough, you must unbolt the shaft and check for stiff, rough joints, and lube the slip-joint.

 

Feel tight is not good enough, you must unbolt the shaft and check for stiff, rough joints, and lube the slip-joint.

What type of T/C do you have??

If it is the ControTrac, it may be sensing momentary differential rotation between the front and rear shafts, causing the T/C to lock in/out of 4x4.

 

Looks like I have a project for Monday. Thanks for the suggestions. I'll have to investigate the T/C. Its the standard Mountaineer type. Thanks