Frame Sag

[mseymour]

Hi, new to the site, was hoping someone could help with my problem. 72 blazer 99% resored, and didnt notice when i had the frame off it was weak. anyway it sags in the middle like alot of the older trucks where the bed rubs the cab, I have had to spacer up the inner body mounts to close the doors etc. I had a buddy with same truck, same problem, and he had steel plate welded under the body center to add rigidity. I know I could weld the frame boxed, but its all been powdercoated.
heres a few pics along the way

[BLUE THUNDER]

Dude, nice rig and welcome from San Antonio. These problems are to be expected with a 36 year old truck. Are you planning to put a top on it? I don't think it really matter at this point, but shimming the body mounts is your best option. Don't ruin the powder coating on the frame. Looks awesome the way it is. What are some of the specs on your ride?

[bouncytruck]

Welcome to the board from Seattle. That's a nice looking rig ya built.

I would suspect the issue is more in the body mounts/frame shims than sagging in the frame.

Are you're rocker/torsion boxes solid?

[vtblazer]

Body issue, not frame...common problem with body off resto's.

Great looking ride, welcome to the board

[Chevyman63]

Originally Posted by bouncytruck

Welcome to the board from Seattle. That's a nice looking rig ya built.

I would suspect the issue is more in the body mounts/frame shims than sagging in the frame.

Are you're rocker/torsion boxes solid?

Originally Posted by vtblazer

Body issue, not frame...common problem with body off resto's.

Great looking ride, welcome to the board

X2

And from Michigan...nice rig!

[1956cameo]

Welcome from the other side of Houston. I too would assume the problem to be with the body and not frame. The truck still looks great!

[Yukon Jack]

Welcome - sweet K5!

[mseymour]

Thanks for the input, similar to what I thought, anyone have a very clean cure? The inside of the body was shot with rhino liner and the underside was bead blasted and painted, so welding is out. I thought about a cage or roll bar that could be modified for support. Some of the specs, full off frame resto, down to the last grade 8 bolt, every piece of metal other than the body was blasted and powdercoated, both axles completely rebuilt, went with 411 posi front/rear, new hubs drive shafts, gas tank, SS fuel and brake lines, rebuilt tranny and transfer case, went with GM HO330 deluxe, all new dash, inst cluster, tilt column, new interior etc.etc.
would like to fix the frame, go efi and drive it more, it has 1600 miles on the odo since the rebuild 7 years ago
I kind of have an itch to start messing with it again
Thanks for all compliments and welcomes
here is a pic near completion
BTW I am the original owner

[Big J]

Welcome to the board. You've got a nice ride. I too don't believe its your frame. Just one of those things when doing a frame off with a blazer. You might have to use a couple extra shims here and there to get it to line up right. No big deal. Theres really not enough distance in between front and rear springs to sag. What are some specs on lift, wheels/tires? Any inside pics? I'm going to rubber line the inside and under side of my tub.

[vtblazer]

Originally Posted by mseymour

fix the frame

It's not the frame.


Shim the body correctly and you'll be all set.

[mseymour]

i think its a combination of both, i have @1.5 inches of shim in the middle mostly under front of the bed, when i put the truck on the lift the flex goes the opposite way. have tried alot of things, so far only the shims work. what bugs me is the flex, the rear tops of the doors rattle and rub the top of the bed
started with 3-4 inch lift but i have removed a spring or two now its @1.5, they are 33's, it handles well, but i have the nitro shocks which are too stiff, gonna go to the hydro's so if any one is looking for nitros i will sell all 4 cheap

[vtblazer]

Originally Posted by mseymour

i think its a combination of both, i have @1.5 inches of shim in the middle mostly under front of the bed, when i put the truck on the lift the flex goes the opposite way. have tried alot of things, so far only the shims work. what bugs me is the flex, the rear tops of the doors rattle and rub the top of the bed
started with 3-4 inch lift but i have removed a spring or two now its @1.5, they are 33's, it handles well, but i have the nitro shocks which are too stiff, gonna go to the hydro's so if any one is looking for nitros i will sell all 4 cheap

Are your torsion boxes intact?

Still betting it's not the frame flexing, it's the mounts letting things move due to the tub being in sub-par condition.

[bouncytruck]

Did you replace the body mounts when you did the resto? Is there a possibility you got the body mounts in wrong or the body mounts?

As you can tell, most of us don't think it's the frame. These trucks have a tendency to flex in the middle when the body mounts are shot. My 72 rubs on the top of the doors just like you are describing. It didn't happen until pulled the top for the first time. I know I need to replace the body mounts to solve the issue.

Since you're the original owner, you'd know if the truck was abuse or wrecked to the extent that the frame is bent. Since you clearly appreciate the truck and spent a lot of time, money and energy restoring it, I'm going to guess it hasn't been abused.

[Jtrux]

Did you put something like these on it??

[mseymour]

yep, they are the polyurethane red mounts, cant remember the name of them, but they also make the stops and bushings for leaf springs etc., yep that was the first thing i checked to make sure they were the right height etc., any ideas to stiffen up the frame/body?

[mseymour]

yep, thats them the energy ones.

[BLUE THUNDER]

If you used the new mounts at the time of your build shimming is the way to go. I wld suggest loosen your body mounts in the area that you are trying to fix and start jacking up the body from the middle of the truck with a 4x4 spanning th rocker boxes til your lines are where you like them and then fill the gaps on the body mounts with shims and you're good to go. Hope that helps. Mario

[AJs72K5]

If you're going to add more shims, or adjust some, I'd recommend loosening all the body mounts on the tub. Otherwise you can cause some binding. It's a very tedious process.

[vtblazer]

Originally Posted by mseymour

put it this way, there is @ a 1.5inch (the amount of spacer) dip in the frame right below the doors, if i put it on the lift or put a jack under the frame, it goes away. the door area is the weak point of the body, as there is no lateral support there

Torsion box & Lower 'A' pillar

Originally Posted by mseymour

I see that they run forward past the doors, but they are in good (solid) shape. what is allowing the sag? again I have to use 1-1.5 inches of spacers in the middle mounts to get the doors to close, other wise the body buckles in the middle

Possibly to much space under the firewall mount

Originally Posted by mseymour

dont have a top, if it was a little more rigid it would be ok, but the flex causes the doors to rub against the bed, rattles and has chipped the paint, I may end up doing some bracing underneath, if i can ever engineer it. I will probably try and find a roll bar for it first and see if I can connect everything

Big project but it does work, it's a band aid though



Everything your describing suggests your body mounts are not correctly adjusted, either not torqued enough, not shimmed enough or could even be torqued to much or shimmed to much.

Also, the torsion boxes ARE what's meant to keep the tub rigid in the door area, that's exactly what their there for, pull the rear cover off and check em out.
How are the lower 'A' pillars looking?
Is there any noticeable rust on the tub?

Keep in mind that these frames are designed to flex, have you compared it to another one to see if there's any differences?

Pics of a "good looking" lower 'A' pillar for ya.
#1 - looks pretty solid
#2 - ...guess not after all.
#3 - Here's the internal support system, it isn't your door openings sagging, it's your firewall moving/flexing here.

[Jtrux]

Originally Posted by AJs72K5

It's a very tedious process.

You're not kidding. No fun at all.

[RED69K5]

I have this same problem with my '72, but I haven't taken it apart yet to investigate the issue. I've read several threads about this issue, and everyone always says shims will fix it. They are probably right, but I don't know for sure. This link to a similar thread might help.

http://coloradok5.com/forums/showthr...Y+MOUNT&page=2

[vtblazer]

Same only different...

[bouncytruck]

Repops aren't made. You'll have to start searching for used ones. If you become a subscribing member, you can post a "wanted-to-buy."