What tcase? JeffinCO had the same issue after going SYEThink I've got it narrowed down to driveshaft or transfer case.
Pulled the tires off the back and driving it slowly doesn't result in any visible vibrations, but noise does eminate from the tcase above a certain speed as observed during test drive. Pulled the driveshaft off and the tcase is quiet, can rev it, chop throttle didn't matter.
So one of 2 things is happening. 1. Driveshaft has a slight bend or imbalance that's shaking the tcase and causing general mayham. 2. tcase got jacked up when I did the sye, and the driveshaft is causing the helical cut gears to move things out of position in a way that's not happening under no load.
Next step is to take the driveshaft to have it examined for balance and trueness. If that shaft turns out ok, time to drop the tcase and see what's going on in there...
205 tcase - was from an 80 so later one w/ slip yoke. Used ORD SYE. Was a bear to do. Broke my snapring pliers wrestling w/ those heavy duty ****ers. Also, the yoke was tight as hell going on those splines. Called ORD about that and they said they're made tight... They certainly were. If I have to pull that thing off again, that's going to be a hardcore. Probably have to use the press.What tcase? JeffinCO had the same issue after going SYE
Turns out my weekend is filled with running around crap....
Looks like you are on the right track to a fix.