OK, guys.
My 88 has always been a bit loud. It also vibrates with the engine -- I put my foot on the floor and I can feel any engine vibration. Same with the steering wheel.

As far as I know, the motor mounts are solid for the 7.3; Is there any way of quieting/"decoupling" the cab from the motor noises?

Thanks,

-Rob

 

Rob
You could use dynamax or this
EZ Cool Car Insulation Kit | Low-E SSR Products

Check your cab mount bushings

 

The motor mounts are NOT solid! Check your motor mounts, they are stiff, but there is some rubber in there. I replaced mine at one point, but can't recall if it made a difference or not.

x2 on checking the cab mount bushings. If they are shot, the cab will be resting on the frame and transmitting vibrations directly. Also check to make sure the exhaust piping isn't touching the cab anywhere.

 

My vibration was the swing bearing on the driveshaft.

 

i have noticed the same thing on mine. I just chocked it up to being an old diesel pickup. She has yet to let me down. Although recently i have been getting a strange vibration upon decel. i believe the carrier bearing is getting tired.

 

Well... I figured I might as well put in some cab mounts.
Couldn't get the middle set loose, but they were still rubber-y. Added 3/4" of shims to the top.
I then found that my right /front/ mount was entirely disconnected. Bolt totally sheared. The left front mount was intact, but worn.
I'll be replacing them as soon as I can, and adding shims... Might as well give myself a little extra clearance.