Question? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

hotrod1 · 05-04-2016, 09:10 PM

Why do you think they put cab mount brackets/arm on these chassis instead of just bolting directly the cab directly to the frame?

**joedoh** · 05-04-2016, 09:40 PM

torque!

torque is force x distance, you can think of it as leverage or advantage when, the farther you are from the point force is applied, the more torque you can apply.

if they mounted the cab to the frame , every part of the body outside of the frame would be subject to torque, leading to doors that dont shut, warped floors, etc, because the weight applied at the door frame would have a force applied between the door frame and the body mount.

so they kick it out as far as they can, using plate steel instead of flimsy sheetmetal, minimize the torque. its why they went away from the center cab mounts too.

hotrod1 · 05-04-2016, 09:43 PM

Ok, good reason. So why are the rear ones closer to the chassis than the front ones?

**joedoh** · 05-04-2016, 10:03 PM

its only slightly, more stepping and pushing and shifting in the front would be my guess

hotrod1 · 05-04-2016, 10:05 PM

Thanks for the info.

One more question. Why are those arms sloped down instead of being level? Lower the cab?

mr48chev · 05-04-2016, 10:29 PM

Quote:

Originally Posted by hotrod1

Thanks for the info.

One more question. Why are those arms sloped down instead of being level? Lower the cab?

If they slope down it's because the crossmember under the bellhousing has been cut out and the frame has twisted due to the weight of the cab pushing down on the cab support brackets.

That is real common on V8 swap trucks with the stock frame that run and automatic. It's also the reason a lot of trucks don't have the hood fitted up right.

The cab will sag until the bottom of the floor is sitting on the frame rails.

hotrod1 · 05-04-2016, 10:31 PM

That's interesting but I have not seen one that was not sloped.

**joedoh** · 05-04-2016, 10:10 PM

they are level with the frame.

hotrod1 · 05-04-2016, 10:28 PM

Quote:

Originally Posted by joedoh

they are level with the frame.

Most of the ones that I have seen on our year trucks are sloped down.

mr48chev · 05-04-2016, 10:25 PM

I want some of what Joe's smokin.

I'd have to say the short version is that the engineers decided that with the wider cab on the AD trucks they wanted the cab supports further outboard Which also saved having to put much stronger supports under the floor.

The other thing is that on the assembly line it may have eased installing the cab on the frame having the supports out where it was easy to connect things.

**joedoh** · 05-04-2016, 11:07 PM

well, the one in your original post is flat. so now you have seen two (the one I posted)

The one I posted is a 53, is it possible you are talking about TF trucks? 55-59?

hotrod1 · 05-04-2016, 11:34 PM

Quote:

Originally Posted by joedoh

well, the one in your original post is flat. so now you have seen two (the one I posted)

The one I posted is a 53, is it possible you are talking about TF trucks? 55-59?

Yep, the one I first posted is flat. I dont know what year it is, but I think that last one is the 55-59.

mphudak · 05-05-2016, 07:08 AM

The original post pic is a 47-55.1 mid body mount for a suburban and panel truck. It is level when it comes off the chassis. Similar to front body/cab mount but is narrower and smaller scale.

If you need any other info on them, let me know. I have a set sitting the in the garage waiting to be put back on the chassis.

05-04-2016, 09:10 PM	#1
hotrod1 56 - autocross Join Date: Apr 2010 Location: Camarillo, Ca Posts: 1,121	Question? Why do you think they put cab mount brackets/arm on these chassis instead of just bolting directly the cab directly to the frame? Attached Images

05-04-2016, 09:40 PM	#2
joedoh Senior Member Join Date: May 2007 Location: Doodah Kansas Posts: 7,773	Re: Question? torque! torque is force x distance, you can think of it as leverage or advantage when, the farther you are from the point force is applied, the more torque you can apply. if they mounted the cab to the frame , every part of the body outside of the frame would be subject to torque, leading to doors that dont shut, warped floors, etc, because the weight applied at the door frame would have a force applied between the door frame and the body mount. so they kick it out as far as they can, using plate steel instead of flimsy sheetmetal, minimize the torque. its why they went away from the center cab mounts too. __________________ the mass of men live lives of quiet desperation if there is a problem, I can have it. new project WAYNE http://67-72chevytrucks.com/vboard/s...d.php?t=844393

05-04-2016, 09:43 PM	#3
hotrod1 56 - autocross Join Date: Apr 2010 Location: Camarillo, Ca Posts: 1,121	Re: Question? Ok, good reason. So why are the rear ones closer to the chassis than the front ones?

05-04-2016, 10:03 PM	#4
joedoh Senior Member Join Date: May 2007 Location: Doodah Kansas Posts: 7,773	Re: Question? its only slightly, more stepping and pushing and shifting in the front would be my guess __________________ the mass of men live lives of quiet desperation if there is a problem, I can have it. new project WAYNE http://67-72chevytrucks.com/vboard/s...d.php?t=844393

05-04-2016, 10:05 PM	#5
hotrod1 56 - autocross Join Date: Apr 2010 Location: Camarillo, Ca Posts: 1,121	Re: Question? Thanks for the info. One more question. Why are those arms sloped down instead of being level? Lower the cab?

05-04-2016, 10:31 PM	#7
hotrod1 56 - autocross Join Date: Apr 2010 Location: Camarillo, Ca Posts: 1,121	Re: Question? That's interesting but I have not seen one that was not sloped.

05-04-2016, 10:10 PM	#8
joedoh Senior Member Join Date: May 2007 Location: Doodah Kansas Posts: 7,773	Re: Question? they are level with the frame. __________________ the mass of men live lives of quiet desperation if there is a problem, I can have it. new project WAYNE http://67-72chevytrucks.com/vboard/s...d.php?t=844393

05-04-2016, 10:25 PM	#10
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 15,498	Re: Question? I want some of what Joe's smokin. I'd have to say the short version is that the engineers decided that with the wider cab on the AD trucks they wanted the cab supports further outboard Which also saved having to put much stronger supports under the floor. The other thing is that on the assembly line it may have eased installing the cab on the frame having the supports out where it was easy to connect things. __________________ Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.

05-04-2016, 11:07 PM	#11
joedoh Senior Member Join Date: May 2007 Location: Doodah Kansas Posts: 7,773	Re: Question? well, the one in your original post is flat. so now you have seen two (the one I posted) The one I posted is a 53, is it possible you are talking about TF trucks? 55-59? __________________ the mass of men live lives of quiet desperation if there is a problem, I can have it. new project WAYNE http://67-72chevytrucks.com/vboard/s...d.php?t=844393

05-05-2016, 07:08 AM	#13
mphudak Registered User Join Date: Jan 2011 Location: Canton, GA Posts: 196	Re: Question? The original post pic is a 47-55.1 mid body mount for a suburban and panel truck. It is level when it comes off the chassis. Similar to front body/cab mount but is narrower and smaller scale. If you need any other info on them, let me know. I have a set sitting the in the garage waiting to be put back on the chassis. __________________ 55.1 GMC Suburban Hydramatic



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