Traveling on the freeway about 70mph, when all of a sudden I get
this shimmy/shake/vibration coming from what felt like the drive train. I let off the gas and it went away, apply the gas it's back. I pulled off to the shoulder looked around the truck and didn't notice any out of the ordinary. As we pulled off the off ramp we feel the same, I put the truck in neutral and coasted for a while and no shimmy/shake. Has anybody had this experience? Trucks at the dealer now and I’m going to take them for a test drive this morning.

 

Sounds like a U-Joint went bad on you.

 

Sat with the mechanic this morning, with the AC on the vibration is there. When he was power braking the motor the vibration got extremely worst. Therefore, without moving the truck it was there. He said something on the line of: something is grounding out (not Electrical). We also agreed on the harmonic balancer could be the problem.

 

harmonic balancer?

You must be the only Lightning with the stock lower pulley still on.

 

We'll forget the pulley, try the heat shields. I had broken welds on both exhaust heat shields. It took them 5 days to figuire out that one. After they narrowed it down and remove them. They drove it and the vibration was gone. The installed new modified shields, and I'm back up a running.
Also I drove it before I paid the bill, so in front of the show room with plenty of patrons I show them what a Lightning can do. About a 100 foot burnout, then turn the corner and did it again for the mechanics. Then I was satisfied.
Have a great day.

 

not the only one