Prothane Body Mounts - Height?

I purchased a set of Prothane urethane mounts for the 1977 K10. I am finding that the mounts tilt the cab forward (rear end higher than front) a few degrees. I am in the process of test fitting new fenders and rad support before heading to paint. Was having an issue getting the fender gaps to align - tight at the top and large gap at the bottom (like 1.5 inches). Thought maybe there was an issue with the aftermarket rad support. So I put the original one back on. No change. Started looking closer at the cab and realized it was tilting downward at the front, at least ever so slightly. So I shimmed the front cab mounts up by 1/4inch with a few washers. Problem solved.

So I am wondering, has anyone used the Prothane mounts before? Any issues with the height (maybe front too short or rears too tall)? Unfortunately I no longer have the original rubber mounts to measure them for reference.

Does anyone happen to know what the height is supposed to be between the cab floor and the top of the frame? I ask because with these mounts it looks like it is sitting really high off the frame. I will snap some pics and post them.

Did you replace the core support mounts as well as the cab mounts?

SquareRoot said:

Did you replace the core support mounts as well as the cab mounts?

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The picture he posted claims its a kit for all if that's what he actually put on. if not, my money would be with you that the core support bushings are shot.

Aren’t all the body mounts the same height?

Quick update. First, yes the kit has all 4 new cab mounts plus the 2 rad support mounts. So all 6 are new.

Next, I did some research and found the same kit from Energy Suspension. This kit -



The helpful thing is the Energy Sus kit's instructions (which are available online) give the height of each bushing. And no they are not all the same -



I measured the Prothane bushings and they match these dimensions from Energy Sus.

So at this point I am just planning to shim the front cab bushings as req'd to get the cab to fender alignment correct. In the temp mockup photo below I have done just that. Ultimately I am expecting that once I get the truck down on the ground and drive it a bit it is possible (likely?) that I will need to make a final adjustment. This truck was taken down to the bare frame, sand blasted (off site - maybe they tweaked it?) and has a completely new 4inch suspension lift. It will probably need a few hundred miles to settle everything into place. For now I am satisfied with the gaps. Will be blowing it back apart for final body work and paint prep. Still waiting on the new Mar-K stepside bed I ordered to arrive. As an aside, I was going to convert to a fleetside, but alas not currently possible unless you find a rust free used bed. Seems the Taiwanese shortbed fleetside fenders are not in production because the fit was so bad all the retailers sent them back. Accordingly to Brothers the Taiwan company has been trying to retool the fenders for the last 12months with no success. Current promise date is 6 more months.

Weird...now I’m wondering. Every one of my 6 bushings were the same. Mine is a K30, but I can’t remember that making a difference bushing wise...

One thing I forgot to post. I need to find (or fabricate) the 6 metal factory sleeves that go inside the bushings. Somehow the 4 for the cab got thrown out during teardown. And the 2 on the rad support have become 'one' with the bolts. Those things are not coming off, ever.

Does anyone know if it is possible to purchase just the metal sleeves? From the places I've looked the only way to obtain the metal sleeves is to purchase the entire rubber mount.

I think LMC, but you might have to buy everything.

Frankenchevy said:

I think LMC, but you might have to buy everything.

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LMC has them Page 20 current catalog item #24 its called a spacer. I kept all my old mounts to compare so I could install them correctly.

That may be you height issue between from and back because that spacer???

Here's a image of my old ones.

I see why I was initially thrown off by how @dhenderz mounts are a different height and mine weren't, his is an earlier year. different style cab mounts altogether.

i tryed 3 different sets of mounts from different company’s for my ‘74 crewcab and non of them were right. i ended up just putting my box on them making the mounts the right height to get things to line up.

Frankenchevy said:

I see why I was initially thrown off by how @dhenderz mounts are a different height and mine weren't, his is an earlier year. different style cab mounts altogether.

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I have the same prothane kit that @dhenderz has exact part number. The lower bushings have a different part number, hence size. There are zero instructions with the kit as to which lower bushing goes to front, rear, or radiator support and why only 2 bolts out of 6 reguired . I'm at the stage in my rebuild, wish I had a shop and the fabrication knowledge of @dhenderz!!!

I found that at the Prothane web site (not the reseller site I purchased my kit from) they have another kit available that also includes spacers for the rad mount (kit #7103). For that kit they include better instructions that list exactly where each of the bushings go. You have to look carefully, but there are part numbers molded into the top (or bottom) of each spacer. From these instructions it will be easy to fab new rad support spacer from some tube. But alas the instructions want you to reuse your existing cab spacers.

Hoagster - thanks for sharing the pic. I looked at the LMC catalog and sure enough $19.95 each for the spacer (yikes!). What is interesting is they only show the spacer for the 2 rear mounts. Your front mounts appear to have spacers as well, correct? Hmmm...

I just swapped my bushings on my 85 last week with the Energy Suspension kit. All six bushings were exactly the same. I couldn't get the body lines to match up so I gave up and figured I'd make spacers at a later time. After a short drive and parking it back in the same spot in my driveway, the body lines were near perfect. Go figure. All the mounting bolts are tight.

dhenderz said:

I found that at the Prothane web site (not the reseller site I purchased my kit from) they have another kit available that also includes spacers for the rad mount (kit #7103). For that kit they include better instructions that list exactly where each of the bushings go. You have to look carefully, but there are part numbers molded into the top (or bottom) of each spacer. From these instructions it will be easy to fab new rad support spacer from some tube. But alas the instructions want you to reuse your existing cab spacers.

Hoagster - thanks for sharing the pic. I looked at the LMC catalog and sure enough $19.95 each for the spacer (yikes!). What is interesting is they only show the spacer for the 2 rear mounts. Your front mounts appear to have spacers as well, correct? Hmmm...

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Sorry for the delay, yes the fronts have the spacer too! As well as the radiator support mounts.