Vibration question for the Hive Mind...

2015 SR5 Dblc. 3" Dobinson lift with long travel rears on Alcan springs. 255/85r16 Km3's that have been religiously rotated every 3k and have 30+k on them. Tom Woods one piece drive shaft. Stock gears

So last week I got to go play in Moab. Couple days of fun and then trying to get up to Top of the World in the snow had a bit of a problem develop that ended up being a few shaved spider gears in the rear end. Rocky Mountain Backroads 4x4 got me up and running so I could go home with a new Eaton E Locker. Ring and pinion were okay and reused. On the way home from Moab (to Wisconsin) I noticed a significant vibration at @75mph and another at @45mph. Never had them before.

Today I rotated the aft end of the drive shaft 90 degrees. The vibration at 75 is gone. The one at 45mph has moved up closer to 48mph but is significantly reduced. I believe a regear (which is in the future...) would solve this as the truck only does the vibration when its in 5th gear, at @ 48mph and turning 1200rpm. Bump it into 4th and it goes away. Short of a regear does anyone have any ideas that I should try to alleviate this problem? Again, had none of these issues before the rear end problem. Thanks in advance!

 

I think we already discussed this in the Wisco thread, but posting here as well to give you a free bumpski and for other people to see.

Possibly torque converter shudder. Simple test to tap brakes, reference the thread below if you want to try it out. (Danger that thread makes my head explode, you've been warned!)

https://www.tacomaworld.com/threads...th-pics-for-second-gen-4-liter-trucks.289913/

Beyond that you're going to have to start playing around with things and see what happens. Vibrations are sometimes nasty gremlins to hunt down. Good luck!

 

If you drive in 4th with no vibration at any speed then most likely torque converter. Had the same issue, replaced torque converter and problem is gone. If you don't want to do the torque converter yet then do a trans pan drain/refill and add a tube of Dr. Tranny Lubegard shudder fix. Should fix the problem temporarily until you're ready for a converter swap.

 

Pretty convinced it is the torque converter at this point. Going to do as MA_TACO suggests and do a drain/fill with shudder fix...