Frame Cracks - How serious?

I have a fair bit of experience with a small wire feed mig welder and no way would I go for the cracks in my frame.

Those are nasty cracks, they are in the main frame rail too, not the added inside box.

Even the professional welders that did my repairs wouldn't warranty them....

Mike

ks wrote:

I was hoping for a more optomistic response ;-)

The second crack is on the inside box right? Thats looking from the engine back towards the tire. See the brake line heading through the frame out towards the tire. Unless I'm misunderstanding you.

First drill a hole, not too big maybe 3/16", in the end of the crack. This will stop it from propagating anymore. Then bevel the crack a bit with a grinder. Then burn the entire thing back together, your mig will work if it is cranked. Don't grind the weld. You might want to add fish plates and gussets, to make it 110%. It will be fine.

--James

I read in an older post:

"In addition make sure the mend plate is not welded on the vertical ends. Since your frame is a stress member the vertical welds will only set up pre stress points for the frame to crack in. Have the plate welded top and bottom but not on the ends. Also, as John said drill the ends of the crack to stop propagation."

Any thoughts on his "no vertical weld" theory?

Trailering this thing to a shop would prove very difficult for me. I

Interesting, yes, you are correct, I didn't realize what I was looking at.

That is a very 'odd' place to have a broken frame. Normally when those frames crack, they go on the inside just by the rear passenger side spring at it's front and on the drivers side rear of front spring.

Was there a winch up front or was it ever 'really' stuck and yanked on hard from the front corner?

I am thinking I am seeing twisting impact damage like if there was a tow hook on the bottom of the front frame corner that got used hard or a lot.

Anyway, in my opinion some jobs are best left to professionals.... That is one of them.

My rear crack was fixed back in 2000 and the last one up front a little bit ago. The repairs have held nicely.

Mike

ks wrote:

You might be right.... no winch, but two tow hooks are on the front.

Here's one of the orignal pics he sent me before I bought it. Notice the strap on that side.....

"stop-drill"

Oh yes, that would be twisting impact damage from strapping.

That Jeep has been well used. If those are the only cracks, you are doing good.

Mine were fatigue from flexing combined with rust cracks.

I would use angle iron on both for a patch. I would drill and try to weld the crack, then put angle iron patches on top of them.

I had to have a piece of angle iron 18" long by 2"x4" put on the outside above the front spring hanger on mine.

Mike

ks wrote:

Frame is in great shape compared to the original body (that I'm replacing right now) ;-)

Heh... this is what my roll cage was mounted to

He was 'mechanically challenged' and decided to have his 99 XJ built up for the trail. I've had it for two years and done my SOA, bigger tires, locker, so those cracks "could" have happened since I bought i, (but I doubt it since I've never had a strap on it).

Not a big deal to me. I'll just fix it and move on. I got it cheap enough that I expected to replace the tub, among other things.

Jeep has been hit (hit or or hit ee) or yanked hard. Something to be concerned with but not a deal breaker by any means. I've seem much worse.

Any frame crack needs to have a fishplate (mend) welded over it, welding the crack itself is useless. (I mean REALLY USELESS!!!) Fishplate should be the same thickness as the base metal, not thicker OR thinner. IIRC, your fame is .104" so some 1/8" plate (.125") would be a good choice.

Drilling out the end of the cracks is a good practice on castings or high alloy frames, I don't think it is really necessary on your low carbon, mild steel frame. Won't hurt.

I do think that the welds should NEVER go across the frame, sort of like a postage stamp "tear hear" Fishplate welds should always go parallel to the frame, preferably right at the edges of the bends on the frame. I'll bend that comment a bit when you use a diamond shaped fishplate like they use in bridges but I still prefer a straight plate welded on the top and bottom edges.

Fishplate should be at least twice as long as it is wide. If the frame is 4", the plate should be 8" or more.

On your Crack_02.jpg, I would use two fishplates, one on the side, one on the bottom, welded at the edge. I hope you can get that wireing loom out of there.

I would rather weld this up with 6011 rod (SMAW) in a stick welder rather than a MIG welder. You want some penetration on crudy metal, not what a MIG does best. This is my choice, use whatever you can get the best job with.

Be sure to do your best at getting clean metal to weld to using a grinder or sanding wheel. A 4-1/2" grinder with 40 grit sandpaper does a nice job.

Cheers.

ks wrote:

I might be taking it to a professional.

Just fround some frame rot under my rear spring hangers. That is probably going to be out of my league. So much for "just" doing a tub swap. Looks like I'm stripping down the frame as well.