I have a '97 Expedition, 80,000 miles, 4x4, auto trans. i need you some advice as this is my first post. So please be gentle guys and girls. Now for the symptoms. When my truck shifts into OD it feels as if it drops into gear. No noises or thuds just seems like it is not very smooth. The fluid has not been changed, but it has been checked and is to capacity. All other gears seem fine. No problems on take off, but I have noticed a shudder when it shifts into OD on the highway. Now for the diff. When pulling up my steep driveway I can occasionally feel the rear end slip or make a light grinding noise. It only does it going up hill with wheels turned to the left. Rear end fluid has not been changed but the level has been checked and is ok. I feel I should start with fluid changes. Any advice or opinions would be appreciated. If fluid changes are suggested should I have the torque conv. drained as well?

 

I'd start with fluid changes. If you don't drain the torque converter you're just wasting your time and money. Over half of the transmission's fluid is in the torque converter.

The rear end can't slip. There are two gears mating. If there is a slip even once it is because a gear has broken, so after that all it will do is slip, it won't work again until it is replaced.

 

it doesnt sound like anything with the rear sounds like a tranny problem, i would change fliud and filter and see if that helps, good luck

 

Thanks for the input guys. I was thinking maybe the clutch packs for the rear end part of the problem.

 

If it feels like your driving over the grooves cut in the road before a stop sighn, then it is a torque convertor shudder during lock up. Like everyone else said, change the fluid, drain the convertor or have a transflush, hold the chemical.