Vibration at freeway speed - need troubleshooting help

[AwwPhooey]

Hello folks, hoping somebody could spare a minute to posit their thoughts on a challenge I’m having.

I have a 2001 XLT 4.0. Original owner ~360K, engine runs like a champ, I take good care of her.

About two months ago started shaking between 65 and 75 mph, seemingly the whole vehicle. It was also drifting a bit to the left, so I took it in and had it aligned and the wheels balanced and rotated. Didn’t change a thing.


Went back to a second shop I trust and had him double check the wheel balance and alignment, and was told everything was spot on and front end is tight. So I figure next step is driveshaft, it’s the original drive shaft with the original U joints.

Got underneath, popped it off and took it to a driveline shop. Had the U joints replaced and the shaft balanced, popped it back in last night. Still no difference. At about 65 to 75 it oscillates pretty noticeably. It’s about eight seconds of oscillation and then it dies down for eight seconds and then ramps up eight seconds more oscillation and then dies for eight seconds, pretty consistently. Whether hitting the gas or coasting.

I’m kind of at my wits end here. Any advice on what more I should consider? The transmission was rebuilt about two years ago from a very good shop (it went 300K before giving out). I really have no other idea on what else to look towards. Pretty frustrated. :/

Any help you folks could offer would be greatly appreciated.

Steve

 

[1998Exp]

I would check the motor mounts (including transmission)

 

[Spudhut]

Just a thought, when was the last time you changed shocks? If your shocks are blown, you will get alot of vibration from the road and what seems like a 'skipping' sensation from side to side.

The only other thing I could think of is your rear end axle and/or pinon bearings....

 

[puzzaa]

Possibly the tie rod ends? Or the ball Joints? Just saying because you said alignment was off. If you notice the steering wheel vibrating a lot more then the body than this could definitely be a place to look. If the tie rods ends are shot they will vibrate the steering wheel at high speeds not to mention if that breaks you wont have steering. Check those boots and make sure they are tightened!

I saw a thread a long time ago about a guy who went mudding in his explorer then posted about vibrations, come to find out mud was caked in the inner side of his rims. He had to powerwash that stuff off and he was good to go. Not sure if this applies to you but just giving suggestions

I had terrible vibrations on mine at higher speeds. Turned out it was the ignition (replaced spark plugs wires and distributor). Not sure which of those fixed it but if I had to guess I would say the wires fixed my problem. Whens the last time you replaced anything ignition related?