I do not normally start threads but this has been a long-standing issue for my car. To me it is not too big a deal. To my wife it makes her stomach feel uneasy. I would like to use 6th when she is in the car. What do you think?

When I first start cruising in sixth I have tiny little drive train vibrations.
I have tried all possible angles of pinion on her and the present setting seems to be the best. Almost gone but, can tell the difference between 5 and 6th gears still. It does appear that after 5-10 miles the vibration goes away almost completely. Is this because the 6th gear gets a little more lube after it is running a while?

It is easy to drive 70-80mph in sixth on a straight stretch like I5. but if you are in the twisty freeway section with any uphill 5th is the way to go. It's not that the torque isn't there. Its harmonics are weird and it just is better to go at it in 5th.

I purchased a 3.5 LPE Aluminum drive shaft a few years back and that helped out a lot. I do have the 1LE trans mount that didn't seem to make any difference. I also have Bilstien shocks, LCA's,Traclink, Adj Pan hard, air bags, and spring isolator delete. All these mod have been made after the original vibration was found and hasn't seems to change the situation. Those mods were made for other reasons but have not made any differences in the drive train vibration issue.

I still think I can improve the issue.... Just have run out of ideas.

What do you guys think?

Any ideas for improvements?