Gap between box and cab???

[69GMC910]

I have about an inch and a half on the passenger side, and 3/4" on drivers side... What causes this and how can it be remedied??

[willett]

Your box is probably sitting crooked on the frame. Loosen the mounts and straighten the bastard out.
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[69GMC910]

Is there that much play in it?
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[andrewmp6]

Or maybe wore out cab bushings on one side?

[tucsonjwt]

I would first get a square (like a big drywall square) and put it against the front edge of the bed and side rail and see if your bed is actually square. You may have had an impact on the rear of the box and the front panel could be tweaked (like one side driven forward 3/4"). Also, eyeball the rear edge of the bed on the side that is closer to the cab - could be pitched forward on the top from a rear impact. Just a thought.

[69GMC910]

The truck has never been in a collision. Family owned since new. It seems to have gotten way worse since I put my new engine in. I'm kinda thinking it is the cab that is the problem. I'll get under it tonight and do some measuring and inspecting...
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[dieseldawg142]

is this the truck with your 496 in it? if so, sounds like you may be tweaking the cab or frame out of shape

[69GMC910]

Thats what I'm thinkin....
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[dieseldawg142]

with a mountain motor in there, have you considered installing poly body mounts? put some in my crew last year, don't know what all the hype 'bout rough riding or noisy is about, i have not noticed much diff. other than the truck feels "stiffer".
no squeaks or amplified noises, smoothness is about the same, but with 38's the smoothness is kind of a moot point anyways
maybe add a bolt in crossbrace in your frame. i've added 2 in my crew, one on the front of the frame(to mount tow hooks & a hitch), & one between the rear wheels(heavy loads on the airbags bent the frame rails in a bit)

[07XCSBZ71]

Replace all the body mounts before you try and line things up, it'll make life easier. My 84 had the same issue, new body mounts fix 90% of it ,then a little adjusting and it was perfect, then a big arse pine fell on it, but thats life. LOL

[69GMC910]

My cab mounts do need to be replaced as they are original. I will be going the polyurethane route as you have suggested. I hope the mounts are my only problem! Are they easy to change? Just unbolt and jack the cab up?
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[69GMC910]

The end of your story really sucks 07XCSBZ71!
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[dieseldawg142]

Originally Posted by 69GMC910

My cab mounts do need to be replaced as they are original. I will be going the polyurethane route as you have suggested. I hope the mounts are my only problem! Are they easy to change? Just unbolt and jack the cab up?
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spray the bejeezus out of them for a few days! use the biggest chunk of lumber you can fit under there to spread the load out. you might be surprised just how hi you have to go to get the old ones out.
when i did my driver side, i disconnected the shifter linkage as it started taking on one heck of an angle.
use synthetic or lithium grease liberally.
oh, & dont leave nothin on your frame rails! stuck a piece of 2x4 between the cab & frame while cleaning up the old mounts, couldn't figure out why the cab & fender were'nt lining up anymore, or the new small dent in the floor. doh!

[riz]

That reminds me of the time I used a small crowbar to put tension on my alternator so I could adjust the belt tension and then 2-3 weeks later I was under the hood and there was the crowbar just laying in the front by the radiator....... how it stayed there and didn't do any damage is beyond me! Lucky I guess.

RIZ

[Keith Seymore]

Originally Posted by dieseldawg142

is this the truck with your 496 in it? if so, sounds like you may be tweaking the cab or frame out of shape

The cab can be set crooked on the frame from the factory (rotated when viewed from the top).

Usually that caused the hood to shoot off to one side and then the fenders/rad support are scooted that direction, too (to maintain the hood to fender gap).

You can tell this is the case if you have a big gap between the fender and bumper on one side and a small gap on the other.

K

[dieseldawg142]

after reading a lot of your stories & advice Keith, seems like they were pretty liberal with body placement on these 'ol trucks!
here i always thought good bodywork was voodoo magic! lol

[Rich84]

The weird thing on mine is that the bumper gap is showing the body has to go one way and the gap to the bed is showing that it will get worse???
I think I need to loosen everything and start over.

[tucsonjwt]

So, if the cab could be tweaked due to improper mounting at the bolts, could the bed be tweaked in the same way? As I recall, there is maybe 1/2" to 3/4" slop in the holes for the bed mounting bolts. If the bed was ever removed to assist in fuel sender/fuel tank replacement, or if the bolts have rusted loose, could the re-install be misaligned? I know left-right tilt is common in these old squares - but maybe that is a spring issue.

[dieseldawg142]

my bed pretty much dictated how it all lined up. i only had about 3/16 play in my bed bolts. new cab mounts & a bit of fudgin' on everything & it's pretty reasonable. when my buddy paints it, he's a pro at that, he'll get it lined up nice.
dont see why you couldn't open up the bed bolt holes a bit to get that extra adjustment

[Keith Seymore]

Originally Posted by tucsonjwt

So, if the cab could be tweaked due to improper mounting at the bolts, could the bed be tweaked in the same way? As I recall, there is maybe 1/2" to 3/4" slop in the holes for the bed mounting bolts. If the bed was ever removed to assist in fuel sender/fuel tank replacement, or if the bolts have rusted loose, could the re-install be misaligned? I know left-right tilt is common in these old squares - but maybe that is a spring issue.

Yes - there is a little slop in the bed bolts, too, such that the bed can be scooted around.

K

[Keith Seymore]

Originally Posted by dieseldawg142

after reading a lot of your stories & advice Keith, seems like they were pretty liberal with body placement on these 'ol trucks!

...one complete vehicle every minute!

Not a lot of time to fiddle with stuff.

The cab thing was worse with a regular cab (because it is so short). As the cabs got longer, like a crew cab or Blazer/Suburban, that tendency gets minimized.

K

[69GMC910]

My front end looks perfect. I'm going to loosen the bed and see what I can do.
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[69GMC910]

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[dieseldawg142]

yeah, you have a bit of difference there. how does your rear bumper line up & look in relation to the rest of the box? looks like you will have to shift it approx. 3/8". if you move your box that much, you mite have to re-align your bumper.
thats a lot movement, like said, maybe you'll have enough slop in the bolt holes, i know mine had hardly any.

[PAWS 72]

I have just replaced mine on both 87's and I had a 1-1/4 gap on each side. Are you sure you hit the holes right on both sides?The two on the very tail end.