Bed, meet cab corner.....

[cpdenton]

Te other night I was driving here in town. I went through an intersection that involves a right hand turn that goes up and over a pretty steep set of railroad tracks. This is steep enough that 18 wheelers are not allowed to go through here because they will high center on the tracks.

There was a loud clunk behind the cab when I was turning that after investigation, was the bed hitting the right rear cab corner. Is this much frame flex normal on a crew cab 92 model? I know the body mount bushings are shot, but the cab does not seem to be sagging much yet, just rubber beginning to look really old. You can also shake the cab quite a bit before the frame starts moving. Will the body mount bushings help with the movement the cab is experiencing?

Thanks in advance.

 

[gandalf]

I couldn't swear that its true, but I seem to recall being told, in the dim and distant past, that our trucks have about a 7 inch travel if you rack them, corner to corner.

That would be sort of like breaking ice cubes loose in an old metal ice tray. You twist the two ends in opposite directions.

 

[junk]

That seems reasonable to me. Especially with bad body bushings.

 

[franklin2]

The cab body and the bed are the only strength the frame really has against twist. If you ever take the bed off for some reason, and then move the truck around the yard without the bed in place, you would be amazed how much the rear frame bounces around. The springs don't do anything, the frame does all the flexing, until you put the bed back in place.

 

[Matrix37495]

Here's a good example of frame flex on a single cab...

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[itsacrazyasian]

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[Matrix37495]

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[Jake_IN]

I couldn't swear that its true, but I seem to recall being told, in the dim and distant past, that our trucks have about a 7 inch travel if you rack them, corner to corner.

Friend of mine broke out his driver side rear window with his bed corner. The OP's condition to me sounds normal. Especially for a crew cab.

Heres a couple pics of my truck up on a stump.

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Pretty sure the bed and cab are touching here.

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[91idi]

I wish I had snapped pics of my super cab on a rock pile. I had 35's and broke the core support. It was so high I had trouble getting back in it. And I'm 6'3" i the pile was about 5-5.5' tall. The body lines were way off

 

[itsacrazyasian]

http://www.facebook.com/photo.php?fbid=10100101646167395&l=fa93bcf65f

try that. crew cab long bed flex. yes the cab has hit the bed under some rather extreme conditions.

 

[cpdenton]

Well, after seeing these pictures, I think my flex is normal. I will replace my body mount bushings soon I think. It has to help some. Thanks for the replies!

 

[gonecrazyi]

I flexed mine so bad that the back cab mount broke and pulled through the cross member cashing the cab to tweak. I'll post a pic when I get on a computer. Its pretty sad looking. Then I blew the front drive shaft tube a part.

 

[MUDKICKR]

so if one would box in the frame of a f350, it would make the truck better offroad due to letting the suspension flex? or it might even ride better by letting the suspension work like it should?

 

[Matrix37495]

I'm far from knowledgeable, but i would think it would make it worse off road. I would think that with everything in good shape the frame flexes to a point then the suspension does the rest. Of course i could be way off too.....

 

[MUDKICKR]

I'm far from knowledgeable, but i would think it would make it worse off road. I would think that with everything in good shape the frame flexes to a point then the suspension does the rest. Of course i could be way off too.....

i can see where your coming from, but offroad your suspension is supposed to put weight to the tires to keep it down, which in turn gives you traction, but if the frame has "flex" in it then it could give a tire less traction by not weighting the tire down enough to have traction. if the frame was more "rigid" then the suspension would have to do more work, which in turn would put more weight to the tires, which could give you more traction.

i guess the best way to explain what im trying to say is to think of progressive rate springs verses linear rate springs, the progressive rate springs are designed to get stiffer throughout its travel, but linear rate springs have the same stiffness throughout there travel.
so if are frame is "flexing", then it would be like the progressive rate spring in which the frame "flexes" so much til it stops to let the suspension take over.