Quote:
Originally Posted by skip72
To start I hope I've posted this in the correct section. I have always wanted a 70's short bed 4WD and well I found what for all intensive purposes my dream truck. 1972 SB step side, 4WD, 350 with a 4 speed.
This evening I was able to remove the bed only to realize my rust issues were far more extensive than just one crack, I found several areas with what I would call significant structural compromise including all 4 leaf perches as well as to the rear cross member and the tail end of the frame.
At what point does a person decide that removing rotten areas and welding in reinforcing plates is no longer an option (I have a very close friend who is a professional welder with many years experience so job quality/safety would not be an issue).
Any help or advise would be greatly appreciated as I am new to the world of these classic vehicles but thoroughly committed to turning this truck into a something that I will use and enjoy for many years.
Thank you in advance
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Well, you have to have enough metal to weld onto, and your dimensions need to be un-altered; hard to straighten a frame that has been reinforced. "X" measure the rear section and check for twisting before considering repairs and straighten first if necessary. I don't see any point in removing the rotten areas. If it don't fall off after wire-wheel cleaning, leave it there and repair on top of it.
FIRST OFF, I don't know much about 4WD frames, not 100% sure they are the exact same size channel-wise, but I'm sure there are others on this forum that can say for sure. IF they ARE, these frame stiffeners might help you on the forward spring perch area provided the rail is straight in that section, but the frame might taper down to a smaller channel on the rearward one like it does on the 2WD, but again, I don't know much about 4WD frames.
If you pursue repairing the old frame, and if the rusted areas are straight enough, these 17" repair/stiffener channels are designed to slip into the frame rail. If the section/s to be repaired are not compatible with the stiffener channels, then I believe a "fish plate" would need to be made, clamped/welded into the frame rails. You might consider boxing for strength after performing fish plate repairs. On the rear, you could extend the fishplate to the end of the frame, all necessary holes can be re-drilled through the old frame through the repair sections. I would not box the end section of the frame behind the rear cross-member for bumper/hitch bolt access. If you do want to box it, weld the nuts holding the bumper/hitch onto the fishplate before you box it with the associated parts installed and aligned for fit. Curved sections, if need repaired, would need to either have curved fish-plates AND/OR boxed (boxed easier, if you have good metal to weld onto) if appropriate for strength required.
All spring perch areas need a plate directly behind the perch mounting point to assure the perch does not pull out of the rail. You would have to remove the rivets holding the perches on, clamp the repair sections in and drill through the existing holes into the repair section. Then, re-install the perches with appropriate strength bolts then weld the repair sections in.
Any time a repaired section can be tied into another repaired section, it makes the unit as a whole a lot stronger.
Sounds like you are working that thing (that's the point, right?) so use caution but with good judgement and your good welder, you can probably make it stronger than a new one.
http://www.classicperform.com/Store/...ck/6372RFS.htm
You can fabricate a rear cross-member fairly easy using appropriate sized angle iron, clamped back to back forming a "Z" shape, bolted to the frame rails top and bottom then welded together, and you could weld it to the fishplate, frame also if desired. IF you are considering a rear tank (I wouldn't), consider the installation of that tank when performing this task. IF you do remove/replace the rear cross-member, take a strong piece of angle iron and bolt or weld it on the frame near the cross-member before your remove it and leave it there until all repairs are finished to ensure the frame does not spring outward or inward. Of course you are going to clean the areas to be welded, but after repairs you might want to clean the entire rear section and POR-15 it to prevent rust in the future.
I wonder how much of this problem is due to the leakage of the wooden bed. Regardless of how you repair the frame, you might take this opportunity to restore the bed while it's off and consider if you are ever going to haul livestock use sealed wood otherwise use some metal like maybe aluminum diamond plate on top of sealed plywood, sealed to the sides of course .
I'd consider repairing it. Replacing the entire frame, you have to find/buy a good frame, and quite a job replacing it. Engine, front diff, transfer case, cab, front end....lots of work. Cutting off a rear section means not losing critical dimensions, but anything can be done right with a tape-measure just measure twice and cut once. Will be interesting to see the pics and who knows, I might then tell you to get a new frame or section.