I have the same symptoms in my car after doing the same work you did. Since my last post on this thread I did more highway driving and tried to recreate what you have done, and it is similar if not exact. I replaced flex discs, center bearing and support, diff support and motor mounts. Marked everything for assembly and took my time torquing everything. Only thing I did differently was that I did switch the axles after replacing the axle seals.

Please keep us posted of your progress. Thanks.

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1980 300TD, SOLD
1984 300TD, 275K
1999 C230 K Black & Tan
2013 C250 Black
1974 CJ5 Red
You might faint from the fight, but you're gonna find it. Every challenge could have paradise behind it. -John Popper-