New cab mounts and the box still sites way higher

[71gmcC15]

Thought it would fix it but nope. I don't know why it's the way it is only thing I can think of is the box is off a 3/4 ton.are 3)4 ton boxes different? Do I need 3/4 ton cab mounts? Haven't bean able to find any difference for 81 ups.

[v30crewcab]

beds are the same. is something rusting out and letting the cab sag?

[71gmcC15]

Originally Posted by v30crewcab

beds are the same. is something rusting out and letting the cab sag?

Got all the rust fixed. The back sapport where fine. Old box lined up good. New box not so much. Only thing I can think of is either 83 up boxes are different. ( Different filler necks and mounting location for 2 bolts) Cross seales taller maby are 83 up cab frame mounts located higher up on the frame to make up the difference?

[v30crewcab]

I've swapped beds between years plenty, and never had it sit like that. might have to shim the rear cab mount. they came with big square shims on the top of them.

[Corts60]

Originally Posted by v30crewcab

I've swapped beds between years plenty, and never had it sit like that. might have to shim the rear cab mount. they came with big square shims on the top of them.

X2. I put an 85 bed on my 78. Lined up perfectly.

[KQQL IT]

I had to shim my 73, figured from the bondo in the gate it's been hit in a past life

[71gmcC15]

Shim the cab. Ok what should I use. Just get a Stack of washers? Cab had no shim before.

[Danmcg]

Probably just the pic but sure looks like the cab is sagging down in back

[Getter-Done]

I have used an 86 bed on a 77 2wd 3/4 ton with no issues.

Then put a 4wd frame under that same cab and bed with no issues.

I'm thinking that the body bushings that are under your truck are for a 1/2-ton cab.

3/4-ton mounts :https://www.energysuspensionparts.com/3.4103

1/2-ton mounts :https://www.energysuspensionparts.com/3.4109

[71gmcC15]

Originally Posted by Getter-Done

I have used an 86 bed on a 77 2wd 3/4 ton with no issues.

Then put a 4wd frame under that same cab and bed with no issues.

I'm thinking that the body bushings that are under your truck are for a 1/2-ton cab.

3/4-ton mounts :https://www.energysuspensionparts.com/3.4103

1/2-ton mounts :https://www.energysuspensionparts.com/3.4109

Thanks for the links but 81 up used the same bushings for 1/2 and 3/4 ton. And the same for 2wd and 4wd. Could I use the older 3/4 ton bushings on my 81 frame?

[Getter-Done]

Originally Posted by 71gmcC15

Thanks for the links but 81 up used the same bushings for 1/2 and 3/4 ton. And the same for 2wd and 4wd. Could I use the older 3/4 ton bushings on my 81 frame?

I should have looked in your signature

Is the cab an 81?

[71gmcC15]

Originally Posted by Getter-Done

I should have looked in your signature

Is the cab an 81?

Yes cab is 81. Frame is 81 only thing that's not is the box that's 84 3/4 ton.

[71gmcC15]

Originally Posted by Danmcg

Probably just the pic but sure looks like the cab is sagging down in back

The cab coner is also not straight the way it's supposed to be making it look even worse. I'm getting that redone with the box and doors

[Danmcg]

Is the body line up by the door handle off too? Hey, no pic so I had to as.
Do the cross sills on the bed look original?
Something weird going on.

[71gmcC15]

Originally Posted by Danmcg

Is the body line up by the door handle off too? Hey, no pic so I had to as.
Do the cross sills on the bed look original?
Something weird going on.

It's off by a bit. Cross seas are original. I squared up the box yesterday and according to it the cab is indeed sagging on the driver rear corner. Don't make no sense but whatever. Going to by a bunch of washers and a longer cab bolt. The passanger side it not to fare off. The bed looking like it was just pushed in a little bit ( sate on the ground) pull it out it should line up.

[Honest Bob]

Its probably a combination of things. It looks like the rocker/cab corner may have been replaced and maybe were not lined up properly or were maybe lined up with the old bed which may have been rusted and sagging? Maybe the pickup box side is bent in? My truck was picked up with a forklift that bent the one side in a little.

Be aware that adding a shim in just one corner is going to throw off door/front fender alignment. I spent hours trying to get things to line up properly after a frame swap only to find a shim lying on the body mounts on the old frame, popped it in and everything magically fit again. It looked like a square piece of steel with a hole in it.

Good luck!

[71gmcC15]

[QUOTE=Honest Bob;9070284]Its probably a combination of things. It looks like the rocker/cab corner may have been replaced and maybe were not lined up properly or were maybe lined up with the old bed which may have been rusted and sagging? Maybe the pickup box side is bent in? My truck was picked up with a forklift that bent the one side in a little.

Be aware that adding a shim in just one corner is going to throw off door/front fender alignment. I spent hours trying to get things to line up properly after a frame swap only to find a shim lying on the body mounts on the old frame, popped it in and everything magically fit again. It looked like a square piece of steel with a hole in it.

Good luck![/QUOTE the corner has bean replaced. It's going to get rereplaced when the box and doors get done. I shimmed up the cab and got the body lines dam near perfect. Didn't help the cab coner out much. I think box may be bent in some. It definitely is on the passenger side the passenger side will line up decent whent that gets pulled out.

[hatzie]

How well does the upper body line align with the bed?

Your cab corner doesn't have a consistent gap with the door. When I weld up corners and rockers I don't remove the door if it's not deformed and I don't have to. It gives me a decent reference for aligning the floor, rocker panel, and the cab corner patches not to mention the fender when I get there. You can open and close the door a bunch of times to verify your progress.

I've had to slice and dice cab corner and rocker patches because one or more dimension wasn't quite right. It's more common than you might think.
For instance: I've had corner patches that weren't wide enough to make a nice straight cab back line and nice straight striker & door gap line without splitting the patch and welding in a section of metal. Rockers that aren't wide enough from the gasket flange to where it lines up with the door are common too. Split it and weld in some metal so things line up properly. Lots more work but it has to be done to make it right.

Something else to keep in mind. GM wasn't the best at making nice body panel gaps. If you aren't working on both sides take a look at the opposite side and make sure your work matches the un-molested factory work. If you're doing both sides you can make the workmanship top notch and most folks will assume it's original. LOL

Modern SUV chassis like the Chevy Traverse and Tahoe/Suburban door gaps to the rocker, dogleg, and striker panels on the rear doors are barely passable from the factory. If your repair is done well and not like the barely passable factory work on the opposite side some people will notice and figure the factory work is your repair.

[71gmcC15]

Originally Posted by hatzie

How well does the upper body line align with the bed?

Your cab corner doesn't have a consistent gap with the door. When I weld up corners and rockers I don't remove the door if it's not deformed and I don't have to. It gives me a decent reference for aligning the floor, rocker panel, and the cab corner patches not to mention the fender when I get there. You can open and close the door a bunch of times to verify your progress.

I've had to slice and dice cab corner and rocker patches because one or more dimension wasn't quite right. It's more common than you might think.
For instance: I've had corner patches that weren't wide enough to make a nice straight cab back line and nice straight striker & door gap line without splitting the patch and welding in a section of metal. Rockers that aren't wide enough from the gasket flange to where it lines up with the door are common too. Split it and weld in some metal so things line up properly. Lots more work but it has to be done to make it right.

Something else to keep in mind. GM wasn't the best at making nice body panel gaps. If you aren't working on both sides take a look at the opposite side and make sure your work matches the un-molested factory work. If you're doing both sides you can make the workmanship top notch and most folks will assume it's original. LOL

Modern SUV chassis like the Chevy Traverse and Tahoe/Suburban door gaps to the rocker, dogleg, and striker panels on the rear doors are barely passable from the factory. If your repair is done well and not like the barely passable factory work on the opposite side some people will notice and figure the factory work is your repair.

Yes the cab corner is messed up. It'd going to get fixed again when the box and doors get done. Not happy with it at all. The passenger side is ok. It he did the driver side last and got in a hurry.

[hatzie]

If the upper body line matches straight along from the cab to the bed then you have a problem with the bedside.

If the cab is lower on that line then you need to replace the cab mounts with the correct height pieces and possibly shim it to match. It's all kinds of fun because the radiator support bushings under the nose are part of the mix. Don't loosen the door hinges. Play with the body bushings til the doors line up the way they do right now then re-align the nose to door body gap.

If your bed has anything of consequence between the frame and bed someone probably did a body lift. Worth looking at. 1/4" chunks of rubber don't count. :-) Lots easier to pull the lift blocks out from under the bed than replace the cab mounts.

I was commenting about how I deal with the door gaps when patching cab corners and rockers in the hopes it would be useful. I wasn't trying to be obnoxious about that door gap.

[71gmcC15]

Originally Posted by hatzie

If the upper body line matches straight along from the cab to the bed then you have a problem with the bedside.

If the cab is lower on that line then you need to replace the cab mounts with the correct height pieces and possibly shim it to match. It's all kinds of fun because the radiator support bushings under the nose are part of the mix. Don't loosen the door hinges. Play with the body bushings til the doors line up the way they do right now then re-align the nose to door body gap.

If your bed has anything of consequence between the frame and bed someone probably did a body lift. Worth looking at. 1/4" chunks of rubber don't count. :-) Lots easier to pull the lift blocks out from under the bed than replace the cab mounts.

I was commenting about how I deal with the door gaps when patching cab corners and rockers in the hopes it would be useful. I wasn't trying to be obnoxious about that door gap.

I got the the body lines dam near perfect now. Had to shim the cab up about a 1/4 inch in the rear. I have come to the conclusion that the box side are pushed in and up making look like the cab is sagging..