alright so i got 135k on a 91 f150 4.9l 4x2 and this has been a problem for about half a year. Ive done research and the symptoms of torque converter slippage match exactly to my issue, I get a shudder in overdrive (some times when changing to 3rd as well) only on light acceleration or climbing a hill. It stops if u floor it or let off the gas when it happens. SO anyway with more research I found out that these early e4od trannys are real garbage and it wasnt until 95 that all the issues were fixed. But anyway I was wondering if just replacing the TC would fix the problem? Ive read that on some fourms but I dont see how it could because the TC's clutch isn't inside the TC is it?? I know that changing the fluid should fix it temporarily, along with additives that supposedly work but I want to find out if simply replacing the TC would fix it. I found some GREAAATTT videos on youtube by davidsfarm about transmissions, in fact its the aod that he dissects have a look!
transmission part1
transmission part2
tourque converters

 

Don't waste time or $$ - get it rebuilt.

 

i had a 94 f150 5.8l with a shutter in mine from 3-4 gear shift and in 4 when applying the gas gently i ended up rebuilding it and it works great had to replace some hard parts that were very hard to find because they updated almost all of the parts in the e40d, so if u rebuilt it you might just have to get a rebuild kit for about 250-300 bucks for a transgo kit with all you need for most rebuilds. then maybe replacing some hard parts about 200 or so bucks so u got 500 bucks in just parts not including taking it out and rebuilding it witch pays between 13-16hrs, rebuild pays 12 hrs and replace pays 3.8 hrs. might want to bring it to a transmission shop n see what they say n just pay and hrs labor. they can hook up a scan tool and unlock n lock the torque converter n what else they have to do.