I have this intermittent problem. When I have to brake hard, as in almost lock it up, I get this
thumping, thudding sound from under the truck when I accelerate agian. You can actually
feel it in the floor. It's almost like someone is under the truck with a rubber mallet. It happend
a few times many months ago and then again this weekend. (I try not to have to brake hard)
Once I get up to speed, it stops. At first I thought it was something in the tranny, like
something didn't release. The first time it happened it really sounded like it came from there.
But another thought is maybe driveline bind? Would this be possible if the braking action
somehow rotated the axle downward and got the shaft out of line? I do have a little clunk
when I take off normally so maybe my slip yoke does need lubed. I can reproduce the
thumping by slamming on the brakes but honestly the noise scares the crap out of me.
Otherwise the truck shifts & drives fine. Any ideas?

 

v-10 , what kind of fluid should i use in my trans i need to replace it this weekend?

 

Checked your rear springs, tranny/motor mounts?

 

Evan,

The 4R100 uses plain old Mercon. Any brand is fine. I've used Vavoline. Drain the pan and tq converter. This will get out all but maybe a qt or two. If you remove the filter be sure to check for the large "O" ring that fits around the filter where it goes into the tranny. Some like to stick in the tranny. You'll need about 14 qts. The pan gasket is reusable.