First off, great forum! Learning more every time I read.

Now to business. I have a 2000 F350 6spd, 7.3, 4x4, dually, CC with 65K Sometimes when I let it lug in the parking lot, it basically feels and sounds like the transmission is bouncing back and forth on it's mounts. Not the engine, just the tranny. I know that's impossible, but that is the feeling I get. The mounts have been checked and seem solid. All the bearings are good and the u-joints were brand new 10k ago.

Any suggestions?

 

Hmmm. My setup is the same as yours and it feels solid as a rock. Are you sure the rear mount is good?

 

I've been paying real close attention to the tranny the past few days and it basically seems like when I have it under load and then put the clutch in really quickly the load releases making everything bounce all over. The mounts all appear intact and strong, but perhaps a crack isn't visible.

 

Well you could try setting the parking brake and putting it in gear and gently give it some throttle. In forward and reverse. With the hood up you should be able to see the motor shift around with the torque load. It's a very good way to verify broken motor mounts.

 

Check the front sway bar bushings. That is exactly what they sound like when they are worn.

 

Maybe it's a driveshaft problem and not the transmission. Have you checked the u-joints? If you have a two piece driveshaft, you might want to check the center support bearing also.

 

You guys are great! The center support bearing has been replaced and my limo is running like a top.