My 4runner starts to vibrate when I hit about 55. The engine gets loud and seems to struggle a bit. I changed the both rear U-joints and ran a diagnostic which only showed ABS sensor problems. It runs perfect at all other speeds, not sure if my drive shaft needs to be balanced? but why would my engine struggle like that at the same time as the vibration? Please give me some ideas where to start....

 

had a similar problem and found it was my ignition breaking down, not sure what yours is...

 

Personally, I would try putting the rear on two jack stands - then put it in drive and run er' up to 55. Just make sure you point it in a safe direction in case it comes off the jack stands.

You will be able to tell quickly if a rear tire or the drive shaft is out of balance.

 

lol wardriver.

If you do go that route make certain that it is secured properly and in front of the car is a large field. Oh and 2 or more people will help.

Other than that I dunno what to say. Sorry .