Body flex questions

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MT1
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Body flex questions

Post by MT1 »

I have used the stock Body mounts to attach my Body to a K5 Blazer frame. Ive noticed some severe frame twisting and body issues that I will be dealing with fairly soon. I also notice that the stock rigs on the stock frame also flex quite a bit. In fact Moorehouse's Wagoneer doors and windows actually bind up in tight flex. My question is where do the body's start to crack and give first? Em kinda of embarrassed to even show this pic but I then noticed that I pulled off the front clip mount loose so the passenger side of the clip is separated from the frame in these pics and stayed with the body allowing the frame to flex with the suspension freely under the rig.

Im thinking seriously about building a modified exo cage / Roof rack, Boxing the frame then tying everything together solid, Welding the cage to the frame and body. The only thing rubber mounted will be motor mounts and tranny tcase mounts. Other than an occasional stress crack can you think of any reason I shouldn't do this? I think I lost a lot of the frame twist strength with the loss of the Blazer body design. Any input would be appreciated.

Notice the front bumper angle compared to the body angle... :shock: On a side note I didnt have any idea this was going on till I saw the pics. Everything felt just fine driving. :D

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Tad
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Re: Body flex questions

Post by Tad »

Besides being a rust bucket I noticed my first real cracks when chopping the cab back behind the C pillar.
All the tops of A, B, C pillars and the rear area right at the body were about to separate at the spot welds, I welded those solid (except for the rear area I cut off, that went in the dumpster).

After chopping the top and going SOA I had the front fenders off for some trimming.
On both sides the cowl area was starting to crack, I have not fixed this yet and the cracks are now 1"-2" long.
I never took pic's but it's right at the upper area that the cowl drains into.

The older frames are boxed a bit different up front (you are on a GM frame IIRC) but I have welded cracks and poor welds up there also. I've also welded cracks in the rear area, near the post mounts and at the welded in xmembers.

Your pic's look like the body mount may have pulled through the lower core support mount. I have an '85 core suport on my '70 frame and the core support has some huge holes for the body mounts. I've used some large fender washers, doubled up to about 1/8" thick and they have been bent every time, but they have not moved/separated like your pic seems to show.

As to the exo/tying everything together thought:
I have not done that but I have a internal hoop that holds my 5 point harness. It's bolted through the floor behind the front seats to a matching plate, that plate is hard mounted to the frame, so essentially no give/play/flex in that.
What happens when I get really tweaked off-road is I hear some really strange sounds, the hoop stays in position with the frame, moving almost to the point where it will hit the door glass (about 1") as the body moves around it.
I'm not sure how to analyze it, the sounds are like cracking welds and stripping bolts, freaks me out enough that I never installed the front A pillar hoop. But I can't find any signs of cracked welds or stripped bolts in that area.

That was long, sorry, so was my day.
My thinking here is that if you tie everything together as you describe and than go flex it like your pic, something is going to give, eventually.
I could be wrong here but I think most frames and bodies are meant to flex and give, both together and independently of each other to absorb and distribute stress.
I actually think (besides some poor welding) that FSJ frames and bodies flex pretty well, even in pretty hard situations.
If I was to weld and tie all that mass together I would just ditch the body and build a buggy like I want for my Rockwells.

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Re: Body flex questions

Post by Stuka »

The GM frame will certainly flex more than an FSJ frame since GM only used C-Channel, no boxing at all. Had a running joke with a friend that his frame twisted more than his suspension (He had a 79 K9 Blazer).

FSJ frames still flex though. My chero's tail gate would not open or close if it was flexed. But a lot of that comes from the body being in bad condition as well. Guys that full box their FSJ frames have basically no flex at all. Same goes for guys that tie full cages into the frame. Ads a LOT of rigidity.

Fully boxed frames are awesome. My JK has ZERO frame flex. Even fully flex out with a tire in the air the doors all open and close as if it was on flat ground. Although some of that is due to it having softer coils, rather than stiffer leafs.
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Re: Body flex questions

Post by MT1 »

I have a tube car build going on as well so Id like to keep this thing streetable. I think for what I will be using it for after the tube car is finished that tying everything together and boxing the frame will most likely out live me. I know those sounds you described... keep waiting to hear the snap of sheared metal or something. Never happens though. You are right the front clip mount just pulls out. Half way through the trip I noticed the rubber missing so I added some big arss flat washers and cinched everything down tight... got home and everything is still in place just pulled apart. :D Crazy leverage. Thanks for the input here guys it looks like its time to put on the metal fab hat again. :-bd
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Re: Body flex questions

Post by lindel »

A friend of mine in Amarillo was flexing his WT on some dirt mounds close to his house with the tailgate open...the amount of frame/body flex was almost sickening. Almost to the point that I thought he'd never get it shut again.
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Re: Body flex questions

Post by MT1 »

I was really interested in the weak spots so I could focus especially on those areas for added support. I noticed this last time out that my tailgate would bind up at times... Keep expecting the windows to start popping and cracking but nothing yet. Ive heard stories of guys actually hearing the windshield actually grind and pop on occasion with out breakage? Thanks for the insight and replies guys. Its really nice to have a place to bounce ideas and FSJ issues off of. Your well thought our replies are appreciated. :fsj:
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