Has anyone had this one? I have a 2001 Excursion 4x4 with a V10 and 3.73 LS. It has 95k miles, new tires, newer ball joints, newer shocks, and drives straight. My mechanic says its tight and needs nothing. But it has a vibration at highway speeds that goes away when I kick it in nuetral and coast. My mechanic suspects tranny, driveshaft, u joint but cant see anything. I'll get it checked out but thought I would post here too.

 

i have a driveline vibration at 73mph and higher. coasting and N dont make a difference. i removed the rear driveshaft and drove it vibration was all gone.

try removing it and driving it with just front wheel drive and see if it goes away or not. easy way to know for sure.

 

i have the same problem, and i replaced the u joints and still have the problem. the only place i notice any slop is the spline where the driveshaft telescopes. i wonder if i need a new driveshaft.

 

The driveshaft spins when you are coasting so it doesn't seem like it's out of ballance. Could it be the U-joints? They are starting to go so you get some vibration under power, but fine coasting?

 

you have a drive pinion to ring gear issue. you might need to adjust your backlash. It will do it on acceleration because the pinions teeth are pressing on the ring gear only at that point.

 

Years ago I spoke to the owner of High Angle Driveline on this issue for a friend. He said to replace the mounting flange for the drive shaft on the rearend. He told me that there were a lot of them that were made and they weren't machined correctly and were our of round making the drive shaft rotate in an oval. Might give him a call. He swore that would fix it.

 

I have a similar problem that has been driving me crazy. Only after 80 kilometers and up on acceleration bad vibrations as soon as I let off smooth as silk. The harder I accelerate the worse it is. However I can hammer WOT from 0 to 80 with no vibration and as soon as I hit 80 it starts vibrating bad. I have been trying to figure out what spins at the same revolutions as the tires.

 

 

 

 

Look at your drive shaft and I bet you have a stock shaft with one Cardan and on the other side u-joint direct.
I had the same issue, problem is your angle and possibly the balance is off but 95% your angle.
My solution, add another Cardan and now your angle wont be an issue.
Best thing I ever did, I can do 100mph + with not a single issue.


See pic.

 

Sounds like the same problem I had on my 03 ex. replaced the DS and all good. It was the slip joint slop.