cab mount question

[erikh09]

Hi all,

I recently swapped my tired old cab mounts out for new poly mounts in my 67 GMC 3/4ton. They did sit about 1/4" or so higher than the old ones but the issue I am having is with the doors closing. The doors closed rock solid with the old mounts in. Now with the new mounts they are both out of alignment roughly 1/4-1/2 of an inch. It seems as though the cab or the doors are sagging? There is no play in the doors if I lift up on them, but when I go to close them, the striker hits below the latch and actually lifts up to close...annoying to say the least since they closed perfectly before I made the change. The floor has minimal rust except in typical places like cab corners, rockers near front of door, and a little on kick panel area. I am not understanding how lifting the cab (which the doors are mounted to) with the new mounts will knock the doors out of alignment. I am sure I am not the first with this issue, but thanks for any advice/tips you can lend.

Erik

[TBONE1964]

How is the cab to bed alignment? Do they body lines match up? Did you have any shims with the old mounts?

If the new mounts raised the whole cab 1/4 inch then you will also need to shim the core support 1/4 inch. Try loosening the core support mounts and see if that help your doors shut better. You may have to shim the cab or adjust the door hinges to fix this.

[erikh09]

Thanks for the reply Tbone... It is hard to tell how the cab and bed align as I believe the bed mounts are shot also. Standing behind the truck the bed sits lower on the passenger side than the drivers side. Also, when the truck idles, the bed shakes a little (engine has mild cam). Also, standing at the front of the truck looking down the drivers side the bed appears to be shifted towards the drivers side about 1/4-1/2". I really think I need to remount the bed, the wood is pretty tired at this point anyway. I do not recall any shims on the old cab mounts but will try to shim the core support to see if that helps with the doors. Seems like all panels are a little out of whack...hood, fenders etc... gaps are less than perfect to say the least.

[MikeyMan]

I had issues when I changed cab mounts on my 71 1/2 ton LWB Fleetside.

My passenger side cab was actually riding on the frame rail. I have pin striping, so I used that as a level line to get the cab height aligned with the bed. My cab mounts seemed a little shorter, so I had to do some shimming. I used my limited carpentry skills and some imaginative fabricating to make the cab sit right. My cab supports and frame mounts had various spots of rot. I ended up fabbing braces and reinforcements to get a couple more years out of this truck. I did not touch the core support mounts, just the four cab mounts.

I got everything leveled and bolted down, and it rides pretty good. My gaps are are less than perfect, too. But, my doors close and latch fine. I recall the door(s) rubbing at times during the jacking process. It doesn't take much to tweak the cab and cause alignment issues. You might try to adjust by adding or subtracting shims/washers.