here is the problem:
between the speeds of 63-71 MPH my truck has a pretty bad vibration. if you get up to about 75 it will smooth back out. at first I though that my tires just needed balancing. well I just put a new set on and the truck still vibrates. I have recently replaced the U-joints on the drive shaft and the rear axle bearings. it is somewhere in the drivetrain and not the engine because I can put the tranny in neutral going down hill and it will still vibrate.
any other ideas?

 

I would remove you drive shaft and get it checked out and make sure it is balanced properly. Do you have a steady bearing? Maybe check that out too if you have one.

MercMan

 

what exactly do you mean by a steady bearing?

 

I had a problem similar to this in my 91 F150, around 70 to 75 it would vibrate, i also replaced the U Joints thinking that was the case, which it wasnt. I had my transmission flushed and two days later it died. I brought it to my mechanic and he told me that the vibration is the clutch in the transmission slipping. Hopefully that's not the case for you but i've heard the same thing from others and that's what their problem was as well.

 

When you guys fugure this out, let us all know because I have been chasing the exact same thing....between 60-73 MPH get the vibration and know it is not in front of truck, more in rear....drivetrain..checked joints, re-balanced seceral times.....????

 

See the post on page 8 of this forum entitled Expensive Tranny Problem. This is where my problem was only i wasnt so lucky and ended up needing a rebuild, sounds like this may be similar to what you are experiencing.

 

have the same problem with a 5 speed. with a new clutch. hope for ideas. just my two cents i think its the junk independent front getting wear on it.

 

tires!!!! you need to have them balanced