Rear spring mount (FWD) frame crack repair.

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As many know the problem with pre 80's 40 frames cracking due to excessive flexing ( cold rivets) and lack of proper support on the cantilever spring mount.
This Arizona rig is cancer free and freshly sand blasted making it much easier to repair the crack and improve the spring mount design.

The crack was only on the inside lower flange of the boxed section. No crack noted to the main frame, however both drivers and passenger side were cracked.
5B40DDA9-EF8F-47F6-A835-3FAE2E30768C.jpeg

The cracks where interrupted by the factory rivet notch.
BBE6191A-7453-4DD3-84B9-A93D435CB13C.jpeg

It's clear from this angle the OEM low profile gusset does little in supporting the cantilever design. My 82 (5 years newer) has a OEM gusset that carries to the top of the frame.
EE011912-8865-401B-B7FC-55F9361CF52F.jpeg

Using some cardboard, two templates were made to translate the pattern onto 1/4" material . Im providing the measurements for anyone interested.
24E3A91C-5374-4CA7-BDD9-2373ECBD5A07_1_201_a.jpeg

The iron worker notcher made quick work of the profile features.
36B82FCA-FE80-4120-9AA4-61CD742849E7.jpeg

Five photo limit...
 
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Checking the fit and measuring for the center plate. It came to 3.125" wide by 5".
16F06AFD-BDC7-4BDD-9452-349758720D76.jpeg

A look at the profile. The rear section (A) also required a small relief for the rivet head to clear.
A9AA16F7-791D-4AA8-A14C-430342DBFB5D.jpeg

The fit looking fwd. The corner weld will provide a strong joint.
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The inside box section was stitch welded to correct any loose fitting rivets from past flexing (Drivers side).
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Prior to burning in the new gusset, both the frame and the inside of the gusset were painted with Zero Rust.
981EC31C-9E10-42AF-A1A9-4DCAF0400A6C.jpeg

More to follow...
 
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The passengers aft view shows the vertical weld only on the OEM gusset. I don't like to weld perpendicular on any vehicle frame. Thats why a good fit up is important. No problem welding parallel on the frame (top).
C425EB33-7D4C-4F8B-82B6-7DE69C032407.jpeg

The front vertical weld is even shorter due to the OEM gusset (drivers side).

EF3825AE-8B46-4D00-94B7-FDFCB51D157B.jpeg

Drivers side rear view.
AC03B8A3-DB7D-4C04-8F2C-5CF4D6D51A49.jpeg

This shot is of my 82. Toyota extended the gussets all the way up the side of the frame.
31362C09-F5F3-4818-BCB9-60173D1F23B6.jpeg

Wanted to share a different fix.
 
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It is hard to tell from your photos but which exact piece has the crack? Why not simply replace that piece?
 

EWheeler

4 Cruisers, No Garage !
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It is hard to tell from your photos but which exact piece has the crack? Why not simply replace that piece?
Its the inner frame c-channel, 2nd photo posted makes it pretty clear:

BBE6191A-7453-4DD3-84B9-A93D435CB13C.jpeg



I've seen a few frames cracked above the spring hanger on the outter frame, trucks that see lots of off-road use would be well served to have these reinforcements to gusset the spring hanger.
 
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Still not clear as to the piece with the crack without seeing an overall picture with pointing out which piece is cracked.

Why not drill out the rivets and replace the cracked part instead of adding all the extra external reinforcements?
 
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Still not clear as to the piece with the crack without seeing an overall picture with pointing out which piece is cracked.

Why not drill out the rivets and replace the cracked part instead of adding all the extra external reinforcements?
The arrow points to the crack inside the frame on both sides.
Removing all those rivets is doable but replacing them not so much. The cold rivet design allows for off-road flexing but once those rivets get loose then excessive flexing will lead to metal fatigue and failure. Stitch welding the areas of concern will certainly help but the design flaw of a low profile gusset on a cantilever hanger need to be beefed up IMO.

The last photo posted shows Toyota's improved gusset that prevents the hanger from over flexing. Not sure what year they implemented it but my 82
has it.
FWIW, the gussets could be made from 3/16", I only have 1/8, 1/4, and way too thick from there in my stock. I could have made it from 1/8 but not wanting to weld vertically on the frame I had reservations on using .125" due to flexing.
I hope that answered your question.

C7D4542D-A8C8-4508-A44D-20D8EBE1F458.jpeg


5B40DDA9-EF8F-47F6-A835-3FAE2E30768C.jpeg
 

pb4ugo

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I wheel a lot, thru the yrs I've had the frame crack and spring mounts break off on both sides. It is a weak design. I like your fix. I'll be doing something similar to my other 40. @B y r o n the 3 rivits with the crack running thru it, hold the spring mount to the bottom of the frame. The frame cracks in the shape of those mounts. I know of quite a few 40"s that had the same issue.
 
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40's that get used off-road will all eventually see this problem if this area isn't addressed....

View attachment 2986521View attachment 2986522View attachment 2986523
Your first photo demonstrates exactly why simply welding won't fix the problem. The welds appear to be of quality but the continuation of flex (stress cycles) results in further cracking along the weld toe. The continuation of stress cycles will result in the parent metal becoming brittle altogether. The fix, is stabilizing the area from those stress cycles.
 
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Still not clear as to the piece with the crack without seeing an overall picture with pointing out which piece is cracked.

Why not drill out the rivets and replace the cracked part instead of adding all the extra external reinforcements?
Looking at the background of the photo, you can see the boxed portion of the frame. These sections run from the forward rear spring perch to the nose of the frame. Held in with rivets and a welded cross member that penetrates the outer frame (also welded). Not impossible but certainly laborious. At the end of the day, as others have stated, the problem would remain until the excessive flexing was addressed.
01AC688C-3AF0-4370-8E17-34664BFB7BFE.jpeg
 

MOTOV8R

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The passengers aft view shows the vertical weld only on the OEM gusset. I don't like to weld perpendicular on any vehicle frame. Thats why a good fit up is important. No problem welding parallel on the frame (top).
View attachment 2986408
The front vertical weld is even shorter due to the OEM gusset (drivers side).

View attachment 2986407
Drivers side rear view.
View attachment 2986406
This shot is of my 82. Toyota extended the gussets all the way up the side of the frame.
View attachment 2986405
Wanted to share a different fix.

Wow super clean work. I had an 82 that stretched all of the bottom frame rivets and I had to weld it to the frame. Even with the added gusset it still was trying to rotate.
 
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Awesome work, you obviously know a thing or two about a thing or two!
Please school me on why you don't like welding perpendicular to the frame.
Good morning and thank you for the compliment.
First let me begin by stating that I'm not a structural engineer or metallurgist but what I can share is 43 plus years of welding and fabrication.
I have worked with many smarter, more experienced men over the years and have been blessed with shared knowledge.
With that said I'll try to explain my statment "I don't like to weld perpendicular (vertically) on frames". Frame dynamics/forces are complicated at best but to keep things simple (I need simple). Take a frame that has torsional forces being applied from flexing, at one point the top is moving inward while the bottom portion of the frame is flexing outward and vise versa. A welded vertical member fighting these forces could result in cracking along the toe of a bead. Longitudinal welds will perform much better over time. Thats not to say welding vertically is never performed on frames, however not preferable. These old frames aren't heat treated per say but the amount of stress cycles is unknown to me. Stated another way, I prefer to avoid welding perpendicular as the Heat Affected Zone (HAZ) from a perpendicular weld basically traverses the dynamic zone. Remember, in most cases a proper weld will be stronger than the parent metal it is part of.
I hope this made sense.
 
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Without getting as technical as firestopper, Don/fc187 routinely cuts all his scab plates diamond-point (double-back diagonal)
Fish plating is common when splicing frames etc.
Basically the material used would be the same thickness of the parent metal. The sides would be twice the distance as the height of the plate.
As for points, I was taught to radius them. If you do use points then don’t weld the tips of said points. Lastly, if the fish plate is large enough, providing holes along the horizontal centerline will be another place to weld. Depending on the repair and material, sometimes fish plates aren’t welded 100%. Other times like when welding high strength steel frames found on off highway haul trucks, the weld might require to continue past the end of a plate then jet upwards. These repairs/changes are figured out by engineers. Most fish plate applications done on a 40 frame will be sufficient.
 
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Good morning and thank you for the compliment.
First let me begin by stating that I'm not a structural engineer or metallurgist but what I can share is 43 plus years of welding and fabrication.
I have worked with many smarter, more experienced men over the years and have been blessed with shared knowledge.
With that said I'll try to explain my statment "I don't like to weld perpendicular (vertically) on frames". Frame dynamics/forces are complicated at best but to keep things simple (I need simple). Take a frame that has torsional forces being applied from flexing, at one point the top is moving inward while the bottom portion of the frame is flexing outward and vise versa. A welded vertical member fighting these forces could result in cracking along the toe of a bead. Longitudinal welds will perform much better over time. Thats not to say welding vertically is never performed on frames, however not preferable. These old frames aren't heat treated per say but the amount of stress cycles is unknown to me. Stated another way, I prefer to avoid welding perpendicular as the Heat Affected Zone (HAZ) from a perpendicular weld basically traverses the dynamic zone. Remember, in most cases a proper weld will be stronger than the parent metal it is part of.
I hope this made sense.
Perfect sense, thanks very much for the insight!
 

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