01 Taco 4dr 3.4L "shimmy" at HW speed

I have tried everything. Alignments, road force balancing, rotation, roadmaster upgrade, etc. No matter what I try or replace, I have a "shimmy" going past 65 mph.

Anyone else have a similar problem or suggestions what to check?

 

have you checked your steering rack bushings?? have you checked the leaf spring bushings, or maybe even the center support bearing on the driveshaft?? check those and see if you have any looseness or if the rubber bushings look bad/cracked.

 

Most speed-sensitive vibrations are due to an out-of-balance wheel. Since it appears you have checked this issue, consider a bent wheel rim (observe and check with dial indicator), out-of-round tire (check with dial indicator), out-of-round wheel rim (check with dial indicator), worn shocks (look for leaking fluid or bounce vehicle), worn steering linkage (looseness in steering), bad wheel bearing (jack and grab the tire top and bottom--should be no wiggle), driveshaft that might be bent or imbalanced (look for dings, no wiggle, or did you change your u-joints and not index the driveshaft). If you have a lazy-man transmission you might have a loose torque converter.

 

What tires and wheel do you have?

How much wait is on each wheel.
LF = 2OZ outside 2OZ inside is an example.

If there is to much weight then the tires needs to taken off and moved around.
Or the tires need to be replaced all toghter.

Also make sure the Wheel and hub are clean and rust free.
make sure your Radiator hoses are flexable. yes these can cause this issue as well.

Checking all your bushing is huge... like HighDesert has written..

Are these street tires or Off Road tires.
If they are off road then you might be doomed.

 

Idk the technical fix for your problem but I know on my 4dr taco. I have about 20k miles on a set of buckshoot mudders. And its werid every once in a while when im rolling about 65mph ill get a shimmer and sometimes it wont go away until i rotate my tires. But just some thoughts could be your tire are getting wore out or maybe there not wearing very good

 

Mine is a brand new 08 double cab 4Wd and does the same thing. Tires rebalanced 2x, nothing. It's subtle but there. Ideas? I seen some sugguest it's the main driveshaft?