just new to this , so please be paitient with me...I've had an '88 Cougar LS 5.0 w/AOD since '99, got it from my Dad when he could'nt drive anymore...anyway, it's had a travelling vibration from day one for me...at Hwy speed it will run through the car from front to back/back to front...the steering wheel vibrates up and down along with the dash...i've had 4 different sets of rims & tires on it...checked and replaced every bearing...checked axles for true...it has been suggested that maybe it is Harmonic Balancer or Flywheel....HELP!! Does anyone have any thoughts??
If it's the harmonic balancer or flywheel you should be able to make it happen while sitting in the driveway - just rev the engine to around the same speed (RPM) the vibration happens and see if you get it.
Could be worn or seized U-Joints as well, or a bent or out of balance drive shaft (it's common for the balancing weights to fall off the drive shaft with age)
Very good suggestions by ThunderChicken
Since you refer to it as a "traveling vibration" I would be checking that Driveline first. New U-Joints both ends and a rebalance. Since the joints are attached to the driveline at both ends take the whole works to a driveline shop and have them go over it. Don't think it would be that expensive.
Yeah its like $100 to balance a driveshaft. That really sounds like your problem too. My 88 is missing a weight on the driveshaft and it kills you to go over 50mph.
A little trick: If your U-joint's weight is missing and you can still see where it used to be you can reduce the imbalance by putting a large hose clamp on the driveshaft and locating it so that the screw part is where the old weight was. Won't be perfect, but it'll help
Heh the weight that came off mine was about the size of 3 (American) 50 cent pieces stacked on top of each other.
Thanks for the great tips...she's going in for some exhaust work this week , will check it then!! All u-joints have been done, just havent checked balance on it! I do get some of the same vibration at an idle, tried shutting off the engine at hwy speed sat., but it didnt change!!