cab mount bushing confirmation

[dfairchild19]

Ive done some pretty heavy searching and cant find what im looking for. Ive got a 3/4" body line gap between the bottom of the fender and the leading edge of the door/rocker on both the driver and passenger sides. This is leading me to believe that one of my rubber bushings could be incorrect. The body is not original to the frame. I will have to double check to be certain but i believe that the frame was originally a 71 K10 frame and the cab and fenders orginally a 72 C10. Therefore, i would think that i would want the rubber bushings for a K10? which i believe is what i have.

I am running a 1" body lift to help with clearance on my swap. The rear mounts look to be very tall for what they are. I also cannot find the receipt from when i purchased them years ago so i cannot confirm what i currently have. It is also worth noting that the bed lines align with the body lines of the cab and door as it currently sits.

I am at a loss as it seems to me that the only 3 options for solution to this is for the rear of the cab to drop down(which would throw off the bed-to-cab alignment), for the front of the fenders to drop down(which cannot currently happen because my intercooler is fixed to my core support and would not allow this), or for the front of the cab to raise up.

i have the gaps shown below as well as each of the mounting points at the frame.

****How can i rotate my images?****

[Ironangel]

Might try getting rid of the aluminum spacers on the core supports...Also make sure that frame aint bent...?

[dfairchild19]

Originally Posted by Ironangel

Might try getting rid of the aluminum spacers on the core supports...Also make sure that frame aint bent...?

With all of the spacers being consistent, I dont think that they would change anything. And as I mentioned, I cant drop the core support because the intercooler sits down lower than the core support.

[JustToxic]

Might want to check see if you got the correct body mount kit. There are two different kits, 2wd 1/2 ton, and 2wd 3/4 and all 4x4. If you got the wrong kit you will run into a similar issue.

Also, if you do have the correct kit. You can try putting a bigger spacer in the forward cab mount.

[dfairchild19]

Originally Posted by JustToxic

Might want to check see if you got the correct body mount kit. There are two different kits, 2wd 1/2 ton, and 2wd 3/4 and all 4x4. If you got the wrong kit you will run into a similar issue.

Also, if you do have the correct kit. You can try putting a bigger spacer in the forward cab mount.

Through the research i have done, I have the 2wd 3/4 and all 4x4 kit since I have the taller rear mount bushing. I have the body mount kit that was originally under this cab on the C10 frame, but they are too short because the gap closes to zero when i let the cab down and the cab hasnt even touched the mount bushing yet, or even come close to touching.

I could try to add a thicker spacer to the front cab mount but I feel like that would be putting a band aid on it instead of finding the root cause and fixing it correctly.

[dfairchild19]

Originally Posted by Ironangel

Might try getting rid of the aluminum spacers on the core supports...Also make sure that frame aint bent...?

Its also probably worth noting that the gap is identical on both the driver and passenger side so it looks to be pretty symmetrical. I wouldnt imagine that the frame would be bent or tweaked perfectly symmetrically.

[GMCPaul]

To correct body lines and gaps the factory service manual species to shim as required. First though you get the maximum amount of adjustment by just torque applied to mounting hardware.

Proper installation requires you to torque front cab bushings to

70-90 foot pounds

rear cab bushings torque to

35-55 foot pounds

They give a range on torque so that you can adjust the body line from cab to bed & front fender by varying the amount of torque applied to the bushing. If the body lines and gaps are not within plus or minus 1/8" then body shims should be added for further adjustment above the top cab mount bushings in front or rear to achieve correct gaps and alignment.

The radiator support mounting bolts torque to 33 lbs

The use of the body lift kit doesn't affect this procedure it just means the cab when done sits higher than normal. You do have the correct mounts installed for a K10 on the cab. In the front at radiator support though are the cushions in reverse position of what they should be, it looks almost like the bottom cushion is on top and the top cushion on bottom. The top radiator support cushion should have a small steel flange collar extending from cushion on bottom side that extends downward into the frame bracket to protect the cushion when fitted into the bracket. The same collar is found on the top cab bushing in front and rear and serves the same purpose.
Paul Jr @ GMCPauls

[dfairchild19]

Originally Posted by GMCPaul

To correct body lines and gaps the factory service manual species to shim as required. First though you get the maximum amount of adjustment by just torque applied to mounting hardware.

Proper installation requires you to torque front cab bushings to

70-90 foot pounds

rear cab bushings torque to

35-55 foot pounds

They give a range on torque so that you can adjust the body line from cab to bed & front fender by varying the amount of torque applied to the bushing. If the body lines and gaps are not within plus or minus 1/8" then body shims should be added for further adjustment above the top cab mount bushings in front or rear to achieve correct gaps and alignment.

The radiator support mounting bolts torque to 33 lbs

The use of the body lift kit doesn't affect this procedure it just means the cab when done sits higher than normal. You do have the correct mounts installed for a K10 on the cab. In the front at radiator support though are the cushions in reverse position of what they should be, it looks almost like the bottom cushion is on top and the top cushion on bottom. The top radiator support cushion should have a small steel flange collar extending from cushion on bottom side that extends downward into the frame bracket to protect the cushion when fitted into the bracket. The same collar is found on the top cab bushing in front and rear and serves the same purpose.
Paul Jr @ GMCPauls

Now this is some great info that I have not seen on the board before in all my years of lurking. Awesome info, Paul!

I do have some questions and concerns with this though:
- will the combination of shimming the front mounts and torquing the rear mounts bring it to within spec?
- Has anyone run into gaps out this bad and brought them back using this method?
- With my bed-to-cab body lines lining up, this leads me to believe that my issue lies in either the front cab mounts or the core support mounts. Surely they dont expect you to add ~1" of shims to any of the body mounts? Im guessing thats how much it will need to be shimmed to bring it back to within spec?
- As good as this info is, I am still concerned that I have further underlying issues.

I will try to mess with it more and see what I can come up with.

Also, i had the core support bushings out to try to drop it to see if that would help correct it and they are in there correctly. This is also one of the areas where I need the 1" body lift to help with clearances.

Thanks again for the info, Paul!

[Getter-Done]

I subbed to hope you find the real issue.
Paul gave very good Detail info.
I need that for my upcoming build.

Is your Radiator support the correct one for your build?

Nice truck by the way.
I know you will get this small issue fixed.
I like the body lift.

[Ironangel]

The support brackets appear to be bolted rather than riveted...That wo uld have me checking for correct brackets at correct height. You also indicated that the bed lines up with the cab, is the bed raised an inch as well? You may find that you have to raise the brackets and/or shim everything up including the bed. The question is why were the frame brackets removed and then bolted? Raising the front of the cab enough to get the gap within tolerance shouldn't throw the bed to cab line up out beyond tolerance...

[rjs53]

I posed this same question a couple weeks ago. I have the exact same issue, with the exact same gap on my fenders and the bed sits a little high now also. I'm going to re torque the cab bushings, maybe I got them to tight. If that doesn't work I gauss I'll shim it.

[dfairchild19]

Originally Posted by Getter-Done

I subbed to hope you find the real issue.
Paul gave very good Detail info.
I need that for my upcoming build.

Is your Radiator support the correct one for your build?

Nice truck by the way.
I know you will get this small issue fixed.
I like the body lift.

The radiator support i did question briefly, but each of the trucks i have had for this build that i have taken pieces from have been 69-72 Chevys. all of these core supports should be identical according to LMC.

Thanks, it is so close to being drivable, i can taste it. hopefully i can get this resolved soon. yeah i dont mind small body lifts to help with clearance of drivetrain parts in this case. not a fan of the big 3" body lifts out there.

[dfairchild19]

Originally Posted by Ironangel

The support brackets appear to be bolted rather than riveted...That wo uld have me checking for correct brackets at correct height. You also indicated that the bed lines up with the cab, is the bed raised an inch as well? You may find that you have to raise the brackets and/or shim everything up including the bed. The question is why were the frame brackets removed and then bolted? Raising the front of the cab enough to get the gap within tolerance shouldn't throw the bed to cab line up out beyond tolerance...

So a bit of a background on this: I had this truck down to its bare frame. I boxed the frame and removed most rivets and welded nuts on the backsides in case they needed removed at a later date(for some unknown reason and I wouldn’t have done it this way in hindsight). I did the same for the forward four bed mounts but they all made it back to their original locations.

The brackets have to be located correctly since they are using the original rivet holes and they flange of the bracket still sits on top of the frame like original.

The bed is on 1” lift blocks as well.

I would like to verify this for 100% certain. Does the factory manual give any info in regards to any of this info so I can confirm by chance?