Frame crack repair best practices? - Pirate4x4.Com : 4x4 and Off-Road Forum

cdaniel · 01-03-2005, 05:12 PM

Got a little feedback on this on IH8mud, but still listening to advice.

I've got some frame cracks on the FJ40 that need to be dealt with. The two easy ones are near the point where the front fender braces attach. The drivers side is on the bottom of the outer box section only. The passenger side has one across the bottom and it travels through a rivet hole and up behind the fender brace. Then there is one in the front crossmember where it attaches to the main frame rail. This one stems from a notch made for a steering shaft to go through. It was welded over before but has since cracked through again.

So, I've got the welding equipment, chop saw and access to a flame cutter to make scab plates and the like. What works and what doesn't with this sort of repair?

Pygpen · 01-03-2005, 05:56 PM

I believe this is covered in the FSM (imagine that!) and is a pretty rare occurance unless there has been some abuse. IIRC, you should drill a hole at the end of the crack to stop it from continueing, and either weld the crack closed and/or weld a scab plate over it. It goes on to show the scap plate with no verticle welds.
Anybody else seen this in the body manual?
PMK

cdaniel · 01-03-2005, 06:16 PM

Quote:

Originally Posted by Pygpen

I believe this is covered in the FSM (imagine that!) and is a pretty rare occurance unless there has been some abuse. IIRC, you should drill a hole at the end of the crack to stop it from continueing, and either weld the crack closed and/or weld a scab plate over it. It goes on to show the scap plate with no verticle welds.
Anybody else seen this in the body manual?
PMK

Someone posted a chassis manual page for me at IH8mud (my manual doesn't have it though

).
http://forum.ih8mud.com/showthread.php?t=30413
It shows what you describe. I'm wondering what's the reason for the angled welds? And what thickness of material is recommended? I've got some 3/16 plate. To much? To little?

FullsizeYota · 01-03-2005, 11:41 PM

angled welds are to minimize breaking again... the weld is going diagonal on the frame thus covering more of the frame (if that makes sense) the frame is more likely to break vertically than it is to break diagonally.... anyone else able to describe this better?

Owyhee Jackass · 01-04-2005, 07:13 AM

I believe FSY is right. The risk is you could develop another crack along the weld, depending on how hot a weld you lay down and the cooling rate of the material, you can induce a stress crack and it will travel along the weld line.

The FSM does show a traingle plate IIRC. 3/16" should be thick enough, I'd go with material thickness as close to the original material as you can get.

01-03-2005, 05:12 PM	#1 (permalink)
cdaniel Registered User Join Date: Aug 2000 Member # 1490 Location: Tempe AZ USA Posts: 75	Frame crack repair best practices? Got a little feedback on this on IH8mud, but still listening to advice. I've got some frame cracks on the FJ40 that need to be dealt with. The two easy ones are near the point where the front fender braces attach. The drivers side is on the bottom of the outer box section only. The passenger side has one across the bottom and it travels through a rivet hole and up behind the fender brace. Then there is one in the front crossmember where it attaches to the main frame rail. This one stems from a notch made for a steering shaft to go through. It was welded over before but has since cracked through again. So, I've got the welding equipment, chop saw and access to a flame cutter to make scab plates and the like. What works and what doesn't with this sort of repair?

01-03-2005, 05:56 PM	#2 (permalink)
Pygpen Granite Guru Join Date: Nov 2001 Member # 8384 Location: Benicia, Ca. Posts: 791	I believe this is covered in the FSM (imagine that!) and is a pretty rare occurance unless there has been some abuse. IIRC, you should drill a hole at the end of the crack to stop it from continueing, and either weld the crack closed and/or weld a scab plate over it. It goes on to show the scap plate with no verticle welds. Anybody else seen this in the body manual? PMK __________________ When the going gets Weird, the Weird turn Pro Benicia, Ca. My Cruisers PMK

01-03-2005, 11:41 PM	#4 (permalink)
FullsizeYota Registered User Join Date: Dec 2003 Member # 24876 Location: Southern Utaarrrr Posts: 1,291	angled welds are to minimize breaking again... the weld is going diagonal on the frame thus covering more of the frame (if that makes sense) the frame is more likely to break vertically than it is to break diagonally.... anyone else able to describe this better? __________________ [COLOR="Lime"]'85 Toyota ext cab. 4 cyl. 5.29s. Chromoly birfs. dual cases. hi-steer. OBA. front ARB. rear welded. cage.[/COLOR]

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01-04-2005, 07:13 AM	#5 (permalink)
Owyhee Jackass Registered User Join Date: Apr 2003 Member # 18654 Location: Southwest Idaho Desert Posts: 497	I believe FSY is right. The risk is you could develop another crack along the weld, depending on how hot a weld you lay down and the cooling rate of the material, you can induce a stress crack and it will travel along the weld line. The FSM does show a traingle plate IIRC. 3/16" should be thick enough, I'd go with material thickness as close to the original material as you can get.