Cracked frame/shock mounts help

Hello all. The K20 project has been sidelined for a couple of years.. wife and I just welcomed our first child (baby boy) into the family. This truck was my grandpa's and was passed to me after his passing. I'm planning on restoring it over the years and being a truck that my son and I can enjoy as much as my grandfather and I did. I was actually with him when he bought the truck when I was young and it was one of the first vehicles I learned to drive in.

I'm beginning to slowly knock the dust off of the build, and planning on taking my time starting with the frame getting blasted and painted. I removed the bed a few weeks back and took the bumper off today. I noticed that the upper shock mounts/frame is cracked where the shocks bolt up (definitely cracked on the driver side frame rail). This truck is a farm/hunting truck and has been used over the years, lol. I was curious as to any feedback/options going forward.. I'm puzzled as to why the passenger side has a mounting tab welded to the outside of the frame whereas the driver side is just bolted directly to the frame? Are there any other alternative mounting options to help with this issue?Thanks for your feedback. See attached pics for reference.

I don't have much to offer as to your frame, but congrats to you and your wife on your new baby boy!

The spots you can,make fish plates plates for,fish plates are a stronger repair than square plates.

What's the difference between a fish plate and a square plate?

Ricko1966 said:

The spots you can make fish plates plates for,fish plates are a stronger repair than square plates.

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Yes, I was thinking about grinding out the cracks and welding back over them. I also saw this alternate mounting brace kit on ORD's website. I may give it a try also. https://www.offroaddesign.com/rear-...87-91-k5-blazer-jimmy-k10-and-k20-pickup.html

mlsceo said:

What's the difference between a fish plate and a square plate?

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Shaped like a fish…

It distributes they weld and load at a different angle than the crack, round the ends to prevent stress risers ,and then plug weld in the center on each side of the crack.

Hottytoddy06 said:

Yes, I was thinking about grinding out the cracks and welding back over them. I also saw this alternate mounting brace kit on ORD's website. I may give it a try also. https://www.offroaddesign.com/rear-...87-91-k5-blazer-jimmy-k10-and-k20-pickup.html

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Those outside mounts are to reenforce the existing frame mount holes for the shocks.
You’ll need to address the frame holes, add the fish plates, before adding the outside mounts.

Very common problem- I’m about to fix mine. Also check where your steering box bolts on. That area tends to crack also.

They also make a brace for it.
https://www.offroaddesign.com/bolt-in-steering-box-brace-for-81-91-gm-4wd-trucks.html

Old Guy Bill said:

Those outside mounts are to reenforce the existing frame mount holes for the shocks.
You’ll need to address the frame holes, add the fish plates, before adding the outside mounts.

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I see. I sprayed the frame with brake cleaner and it gives a better visual of the crack. I’m assuming that the fishplate would cover the whole crack on the outside of the frame, correct? It looks like it would be a challenge to get it to form exactly where this crack is around that mounting hole. Thanks again for your suggestions. I attached this pick for a better reference. Driver side outside of frame rail.

The plate on the one side is a previous repair, as well on the other side the weld is a previous repair. You need to drill out all ends of all the cracks. This will prevent them from spreading anymore, the cracks will keep spreading even if you weld them up without drilling them.

Offroad design offers outer shock support braces for pickups as well.

@PrairieDrifter is giving you good advise on drilling the ends of the cracks.

Everyone gave great advice, and the ORD braces are also a great idea, I run them on my truck as well. One thing I'll add... I'm not sure if this was the cause or not, but never use air shocks or those shocks with helper springs built in on these trucks (or any truck for that matter).

I wouldn't sweat this too much, just do a good job welding when you add the plates and it'll be better than new. Based on what I can see in your pics it still looks like a nice frame.

Excellent thread-info. My frame is ok, but I ordered the reinforcement kit from ORD in a preventative mode. Would you use a larger piece of steel (like a glorified fender washer) on the backside to reinforce/support the shock mounting hole?

I did this when I made mounting brackets for the rear sway bar too.

Doppleganger said:

Excellent thread-info. My frame is ok, but I ordered the reinforcement kit from ORD in a preventative mode. Would you use a larger piece of steel (like a glorified fender washer) on the backside to reinforce/support the shock mounting hole?

I did this when I made mounting brackets for the rear sway bar too.

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My frame was solid, no cracks, and I didn't do anything to my frame when I did the frame off, I just added those ORD braces. I take my truck to the dunes a lot, I've gotten air a couple times, and drive it hard through whoops quite a bit and no issues at all. I think what makes these crack is using either air shocks or some sort of lift shock on them, or maybe a bad shock that's binding. I personally have never cracked a frame here, and I've had a LOT of squares over the years, but I also never used lift shocks on the back.

I did have an 89 Blazer that I used for plowing and put helper shocks on the front of that (shocks that have springs in them). I did crack the front of the frame on that where the shocks mount.