Pulled the truck out of storage after almost a year and never resolved the problem since. I know alot of you had the infamous 75-90 MPH vibration which I feel is related but not the cause of the driveline.

As I was warming the truck up, I revved and held it at 3500 RPM and noticed the vibration...bad enough to make the seats shake....similar to what I was experiencing at 75-90 MPH. It feels like the torque convertor was out of balance or the exhaust might be transmitting through the frame. A year ago I installed the Ford factory exhaust isolators which did nothing and the truck has a Bassani cat back system. I have a hunch it still might be exhaust related but wondering if anyone found a resolution since last year.....

 

anybody check to see if the driveshaft was out of balance???

 

still got it, did it with all 3 sets of wheels
and tires that ive had,tried an exhaust
balancer thing didnt help either.havent played
with the driveshaft yet.

 

I'll bet its the DS. My old chevy pick did the same thing.

 

As previously stated, The vibration occurs with the gear selector in park and engine held at around 3,500 RPM. Obviously the driveline isn't an issue at this time since the vehicle is stationary. Since the RPM is in the above range at 70-90, and it occurs while in park, it seems like more of an Engine/Exhaust related problem rather than driveline.....Although it might be a contributing factor at speed. First things first.......

I think the problem is poor isolation from the exhaust even though none of the pipes actually contact the frame. Anyone reset their exhaust?