Got a 2wd '01 F-250 and I recently had my front trnny seal replaced after it blew while backing my boat into my driveway. Had the seal replaced and shop said the torque converter looked good and fluid/screen looked clean so back it went.

Just got my boat out and started towing again and now I'm noticing a definite shuddering/pulsating in first gear while under heavy load. Only seems to happen when I'm towing. Boat weighs ~5,500 lbs.

Does this sound like my torque converter slipping?

 

My first thought is check the driveshaft carrier bearing. I've read a few posts about that causing a vibration - especially when first starting off with a load. Mine does it a TINY bit 'cause I changed the 2" rear blocks to 4" without changing the carrier bearing spacing. Good luck and hope it's NOT the tranny!!

 

Thanks Cat_man. That makes a lot of sense cause I did recently add an additional 1.5" of spacer blocks to the rear to level the truck out and I didn't change the spacing on the bearing either. I hope you're right.