My 97 F-150 did the same thing as you describe at 80,000 miles. I have a 5.4 and E4OD. I changed fluid and filter and added 1 bottle of Lube Gard available at NAPA. It has almost cleared up the problem. I now am approaching 110,000 miles and am needing to do the fluid change again and will add the Lube Gard again. I suspect it is a very similar product to the product Ford sells. It seems to be a highly regarded product and not a snake oil. By the way use the Lube Gard in the red bottle if you go this route.

 

My 96 cougar 4.6 had TC shudder. The fluid additive worked for only a short time. Ultimately, i had to have the trans rebuilt. The T-birds and Cougars are nortorious for torq converter shudder.

When the trans up-shifted from 2nd to 3rd gear (35-40 mph) you swear you were driving over railroad tracks.

just my 2¢ of

-hooD

 

2/1/04 Well, I took my truck to a transmission shop and their top mechanic road tested it and told me it was the transmission "tail" bushing". Worn prematurely by a minor vibration in my 10' aluminum driveshaft. He said I would eventually have to replace the bushing again unless I had the driveshaft balanced.