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My frame is sagging, or bowing in the middle [message #297665]

Sat, 19 March 2016 14:15

RF_Burns

Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada

Karma: 3

Senior Member

I had noticed some ripples in my body panels and that my rub rail did not appear to be striaght. So today I pulled a string line on both sides along the rub rail using the marker light screws as a reference. Sure enough my coach body is higher in the middle and sags to each end. Its about 5/8" on the passenger side and 1" on the drivers side.

So then I did the same thing along the underside of the straight frame rails. I used jar lids as spaces on each end to clear the bogie mount. The middle of the passenger side is about 1/2" higher than the ends. On the driver's side its about 5/8" difference.

The middle body pads are squished more than the ends, so the center of the frame is taking more weight than the ends.

Is this normal? I'd like to fix it since its causing cracks in the body seams.

I've posted some photos. sorry about the poor quality, the dawg was trying to help.

http://www.gmcmhphotos.com/photos/g6922-frame-sagging.html

Thanks for any ideas.

Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that

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Re: My frame is sagging, or bowing in the middle [message #297666 is a reply to message #297665]

Sat, 19 March 2016 14:52

Harry

Messages: 1888
Registered: October 2007
Location: Victoria, BC CANADA

Karma: 3

Senior Member

That seems odd. Do you have anything heavy hanging off the back end?

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Re: My frame is sagging, or bowing in the middle [message #297667 is a reply to message #297666]

Sat, 19 March 2016 15:06

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

Only the top of the frame needs to be level, not the bottom. Before I got too hung up on the frame being a problem I would be looking at the body isolators. It is very common for them to collapse or fall out. Faye Curtis and Jim K. both have a replacement kits available.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

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Re: My frame is sagging, or bowing in the middle [message #297669 is a reply to message #297665]

Sat, 19 March 2016 15:43

RF_Burns

Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada

Karma: 3

Senior Member

I replaced the body pads with the thick version about 4 years ago.

I may have found part of my problem. I could not get the big bolts on the corner pads to loosen, so I used some split washers to raise the mounting plates for those pads. The rear pads came up 1/4" when I loosed them. I can't put any more washers in raise them any more as there is not enough thread left for the nut. I have a permanent bed at the rear so I will need to pull that out to access the top of the bolt.

Those donuts look in good shape so I may be able to slide in 1 or 2 large washers on top of the donut to take up the space.

However, putting more weight on the ends of the frame will just make my sagging frame problem worse.

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Re: My frame is sagging, or bowing in the middle [message #297670 is a reply to message #297665]

Sat, 19 March 2016 15:44

RF_Burns

Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada

Karma: 3

Senior Member

Harry,
The only thing hanging off the rear hitch socket is a pair of bicycles.

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Re: My frame is sagging, or bowing in the middle [message #297671 is a reply to message #297670]

Sat, 19 March 2016 16:09

Harry

Messages: 1888
Registered: October 2007
Location: Victoria, BC CANADA

Karma: 3

Senior Member

How about checking the interior floor for level?

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Re: My frame is sagging, or bowing in the middle [message #297681 is a reply to message #297669]

Sat, 19 March 2016 21:02

Ken Burton

Messages: 10030
Registered: January 2004
Location: Hebron, Indiana

Karma: 10

Senior Member

Go look to see if any of the new pads have fallen out.

Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

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Re: My frame is sagging, or bowing in the middle [message #297685 is a reply to message #297665]

Sat, 19 March 2016 21:13

RF_Burns

Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada

Karma: 3

Senior Member

Ken, all the pads are there.. I glue and screwed them so they would stay put.

I did manage to get the rear donut bolts out. The donuts looked good, were not cracked. I was able to get 2 large washers between the upper donut and frame. This took made up for the thicker pads. The body has come back a tad now.

I tried the front bolts but I can't get enough torque to loosen either side. I can only get a box end wrench on those. I'll take off the wheels tomorrow and see if that helps.

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Re: My frame is sagging, or bowing in the middle [message #297693 is a reply to message #297665]

Sat, 19 March 2016 22:54

Gadabout

Messages: 124
Registered: March 2013
Location: Edmonton

Karma: 2

Senior Member

Is it possible that the the body panels are losing there form ( wide hips) ?

The Aluminum, "Beam" Frame construction of the GMC Body is much strong than then Suspension Frame that the body rides on. In the center area of the coach, I think of the body as holding the Frame Up more then the frame holding the body up.

Your can easily see the bottom of the Aluminum Beams between the outside of the body panel and the Suspension frame.

Using a long straight edge spanning 3 or 4 of the beams, see if you can detect any sag in the floor of the coach.

At the front and rear there two rubber isolators that support the body from the suspension frame. I have seen rubber isolators that were cracked or otherwise deteriorated. If these isolators are damaged or missing, I suppose over a period of time it could cause the body to sag or twist at the front and/or rear.

Good luck with it...

Carl Harr : Driver NASCAR Pro Series #2
1978 Gadabout-Restoring
1978 Palm Beach
1976 Glenbrook
Prevost Featherlite H3-45

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Re: My frame is sagging, or bowing in the middle [message #297719 is a reply to message #297665]

Sun, 20 March 2016 10:59

Carl S.

Messages: 4186
Registered: January 2009
Location: Tucson, AZ.

Karma: 13

Senior Member

This may sound stupid, but did you make sure the string is REALLY tight? In my construction career, I have worked with a lot of string lines and they can sag more than you think they would even when you have them fairly tight. A better way to measure it would be with a laser.

Carl Stouffer '75 ex Palm Beach Tucson, AZ. Chuck Aulgur Reaction Arm Disc Brakes, Quadrabags, 3.70 LSD final drive, Lenzi knuckles/hubs, Dodge Truck 16" X 8" front wheels, Rear American Eagles, Solar battery charging. GMCSJ and GMCMI member

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Re: My frame is sagging, or bowing in the middle [message #297720 is a reply to message #297665]

Sun, 20 March 2016 11:09

RF_Burns

Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada

Karma: 3

Senior Member

I managed to get the front frame mounting bolts loose this morning. Added some large washers between the donut and the body as I did to the rears to make up for the thicker pads.

Carl, I have the strings pulled as tight as my makeshift setup allows. I have a DeWalt laser, but it gives a level horizontal and vertical line. I had tried it but its not the proper tool for the job.

Its much nicer working in the new shop than the first time around in the driveway.

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Re: My frame is sagging, or bowing in the middle [message #297726 is a reply to message #297665]

Sun, 20 March 2016 12:42

Adrien G.

Messages: 474
Registered: May 2008
Location: Burns Flat, OK 73624

Karma: 1

Senior Member

Bruce,

PM sent.

Adrien & Jenny Genesoto 75 Glenbrook (26-3) Mods LS3.70 FD / Reaction Sys / 80mm Front&Intermidiate / Hydroboost / 16" Tires / Frame Rebuild / Interior Rebuild Yuba City,Ca. Text 530-nine-3-three-3-nine-nine-6

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