Check the big bearing that supports the center of the split driveshaft in the rear(can't think of what it's called right now...duh). I've read a lot of posts where that support bearing was the culprit of this exact same type of problem. I doubt it's your tranny causing the shudder. Might be tight(or loose) u-joints too.

David
?'90 Trooper?2.6L?Auto?DELTA Cam?AMC Head?"DN" Lift?SlakAzz Sliderzz
?TrXus M/T's?Black Rockcrawlers?Lockers by MIG & ARB?ProComp ES9000's
?Pics and junk...Thx Tad!!