Replacing bad frame mount points, what's best?

[derf]

Replacing bad body mount points on the frame, what's best?

So as I get my frame on jack stands and I'm checking everything out, I am reminded that a couple of the body mount points on the frame were pretty badly rusted. They're rusted very thin right where the body mount bushing sat. I tossed on a coat of Rustoleum primer when I stripped the frame all those years ago so they haven't gotten any worse. But they're pretty bad. If there's a time to fix it, its now when the tub is off the frame and I have complete access to it.

What's the best way to fix this kind of problem? I've thought about cutting out just the rusted section and cutting a piece to match and welding it in. I've also thought about replacing them entirely. I can just cut/grind them off the frame and weld on a replacement part. That is, if I can find a place that sells replacements.

What say you all? Which route would you take to fix this problem?

 

[giantsfan]

found these on quadratec.com, hope this helps.
i would just cut them off the frame looks like it wouldn't be too tough.
Advanced Frame Works BDMNTS 6 - Replacement Frame-to-Body Mounts for 76-86 Jeep® CJ-5 & CJ-7 - Quadratec

 

[IOPort51]

Re: Replacing bad body mount points on the frame, what's best?

personally I would do as little welding on the frame as possible. I would repair the mounts rather than replace them.
You could quite easily make an overlay to weld on the top of the mount. A 1/4" plate would not upset the body height at all and you could just use a 1/2" of weld on each corner. you would end up with mounts that were reinforced at the week points but still with the factory welds to the frame.

So as I get my frame on jack stands and I'm checking everything out, I am reminded that a couple of the body mount points on the frame were pretty badly rusted. They're rusted very thin right where the body mount bushing sat. I tossed on a coat of Rustoleum primer when I stripped the frame all those years ago so they haven't gotten any worse. But they're pretty bad. If there's a time to fix it, its now when the tub is off the frame and I have complete access to it.

What's the best way to fix this kind of problem? I've thought about cutting out just the rusted section and cutting a piece to match and welding it in. I've also thought about replacing them entirely. I can just cut/grind them off the frame and weld on a replacement part. That is, if I can find a place that sells replacements.

What say you all? Which route would you take to fix this problem?

 

[derf]

Re: Replacing bad body mount points on the frame, what's best?

personally I would do as little welding on the frame as possible. I would repair the mounts rather than replace them.
You could quite easily make an overlay to weld on the top of the mount. A 1/4" plate would not upset the body height at all and you could just use a 1/2" of weld on each corner. you would end up with mounts that were reinforced at the week points but still with the factory welds to the frame.

That's a good point. Though I think 1/4" plate is overkill considering the factory mounts are at most 3/16" but I think just laying a piece over top of the factory mount and welding it on wouldn't be a bad idea. It would be easier than trying to get replacement mounts lined up straight.

 

[Old Dog]

I just welded a new top plate on mine years ago and they have been fine.

 

[derf]

Well, a drill press, hole saw, sawzall, torch and welder I have. I'll have plenty of metal when I pick up all the other stuff I need this week. I think I have a plan now. New top plates it is...

 

[CJKrawler]

Re: Replacing bad body mount points on the frame, what's best?

personally I would do as little welding on the frame as possible. I would repair the mounts rather than replace them.
You could quite easily make an overlay to weld on the top of the mount. A 1/4" plate would not upset the body height at all and you could just use a 1/2" of weld on each corner. you would end up with mounts that were reinforced at the week points but still with the factory welds to the frame.

Why not weld on the frame?

 

[IOPort51]

Re: Replacing bad body mount points on the frame, what's best?

believe it of not they don't make jeep frames out of the best steel in the world. In fact as steel goes it is , but it is suitable for the forming and stress it is put under. but it doesn't weld for poopie. It is also true than the heat input from a good weld could drastically change the properties of the frame steel and lead to more saver problems that it cured. as an indication of how well it welds , take a look at a factory weld. I don't know anyone that even fantasizes about being a welder that would call that a good weld. apparently it is just good enough.
But, as usual its your frame do what you will and I am sure you will not be the first to do it.

Why not weld on the frame?

 

[CJKrawler]

Re: Replacing bad body mount points on the frame, what's best?

believe it of not they don't make jeep frames out of the best steel in the world. In fact as steel goes it is , but it is suitable for the forming and stress it is put under. but it doesn't weld for poopie. It is also true than the heat input from a good weld could drastically change the properties of the frame steel and lead to more saver problems that it cured. as an indication of how well it welds , take a look at a factory weld. I don't know anyone that even fantasizes about being a welder that would call that a good weld. apparently it is just good enough.
But, as usual its your frame do what you will and I am sure you will not be the first to do it.

That is something I had never heard. I have some welding I need to do on mine, so I guess I will just replace the tops of those like Old Dog did.

 

[73CJ]

Re: Replacing bad body mount points on the frame, what's best?

believe it of not they don't make jeep frames out of the best steel in the world. In fact as steel goes it is ,

Frames are made of low carbon steel (1020 etc) Why would they use a medium or high carbon steel? They aren't heat treating it.

Low carbon steel welds just fine with the proper preparation. The factory welds aren't show quality, but do have proper penetration for a sound weld joint.

The key is adequate preparation - clean! Most crappy welds weren't cleaned right and are cold welds. Not enough amps used while welding. You can't weld over rust or paint and get a good weld joint. The factory was welding on clean steel.

If you can't weld correctly, take it to a pro who can.

 

[IOPort51]

Re: Replacing bad body mount points on the frame, what's best?

excellent points 73CJ

its is "low carbon" but not something as exotic as 1020 or a-36. when you use that much of anything the steel mills make a material just for you. criteria inexpensive (relatively) and very form-able. known in the trade as "rim" steel. Heat treating is not the only way to make steel harder, the act of forming increases the hardness my a very impressive amount not to mention the vibration of 30 or 40 years of use. Frames don't crack because of impact as much as the stress points become work hardened.
So what happens when you anneal a load bearing area that can not possibly have avoided work hardening over the years. And then of course you have to consider the stress caused by the new weld on the "low alloy" steel in a load bearing position, I guess you could anneal the frame if you had a furnace large enough to hold it at 1500 deg. for a couple of hours.
The factory was working on clean new steel, you may not expect show quality but you mite think they would d better than buzzard if it were possible.
like I said, it's your rig do what you will, life is for learning. For me, there is enough evidence to cause me to avoid this if at all possible. derf does not really need to so why take the chance?
One other item, if you decide you want to try this, don't use a mig welder. If that is the only machine available to you, at very least, use flux cored wire and not gas shielded hard wire.


"If you can't weld correctly, take it to a pro who can."
I can, I am and I still wouldn't.

Frames are made of low carbon steel (1020 etc) Why would they use a medium or high carbon steel? They aren't heat treating it.

Low carbon steel welds just fine with the proper preparation. The factory welds aren't show quality, but do have proper penetration for a sound weld joint.

The key is adequate preparation - clean! Most crappy welds weren't cleaned right and are cold welds. Not enough amps used while welding. You can't weld over rust or paint and get a good weld joint. The factory was welding on clean steel.

Ifyou can't weld correctly, take it to a pro who can

 

[derf]

Re: Replacing bad body mount points on the frame, what's best?

One other item, if you decide you want to try this, don't use a mig welder. If that is the only machine available to you, at very least, use flux cored wire and not gas shielded hard wire.

That's all I have right now. I don't have the bottle for my welder yet and I have a couple of big spools of flux core to burn through.

 

[CJKrawler]

I have a stick welder that I will be working with, and, as always proper prep is essential in anything you do. Thanks for the advise. I will keep that in mind as I am planning upgrades. I do know that as I move along, I will be welding on the frame, I will just keep it as minimalistic as possible.