Frame cracks around upper shock mounts

[jumbowolfe]

Topic split from 76 C10 Project

@jumbowolfe

Mine's not cracked, but I'd really like to have it welded it just to make sure it never does.  The extra bracing, i'll look into as well.

Speaking of, are there any sites that sell a bracing/boxing kit for the back of the frame around the bed area, where cracks have formed around the shock mounts?

The thread, "cracked frame 79 k10" addresses your concerns.

Welds concentrate stress in the vicinity of the welds - so if no cracks preexist in the frame around the steering gear, you should be okay with the bolt-on reinforcement kit by itself.  The bolt-on kits are totally non-invasive and prevent tin-canning (levering) of the frame rail face.  The weld-on kits are best suited to repairing frames already weakened by cracks.  If a vehicle is to be used aggressively off road, I recommend pairing the weld-on and bolt-on kits.


Now, regarding frame cracks that develop around the upper shock absorber mounts...

Front shock mounting:
I haven't seen any 'kits,' per say.  But some factory GM 4x4s use 3/16" steel brackets to augment outboard support of the front, upper shock pin mount.  You may have to fabricate your own brackets out of 1/4" steel plate and attach them to the frame using Grade 8 flanged frame bolts.  Careful measurement is crucial to the outcome.

Rear shock mounting:
GM's biggest issue with frame cracking around upper shock mounts occurs at the rear.  Frame cracks, when they develop, are typically starburst, radiating outward from the shock mount hole (right side), or are sub-concentric with the shock mount hole (left side).  The repair solution is to terminate the cracks with 1/8" drill holes, v-groove and weld from both sides.  Then dress the frame down and weld 3/16" thick reinforcing washers to either side of the frame.  Unfortunately, cracks will eventually reappear around the circumference of the welded washers, requiring subsequent rewelding and repair.  Longer service intervals may be achieved by using washers of dissimilar outside diameters to help disperse rigidity of the repair areas. 

But, for a bullet-proof repair, regardless of whether or not cracks have yet developed, adapting the concept from the front shock mounting on four wheel drives, "full wrap brackets" can be fabricated out of 1/4" steel plate that support the outboard ends of the upper shock pins.  If done correctly, this will virtually eliminate tincanning and (re)cracking of the frame.  Again, the idea is to design the supports to increase rigidity of the upper shock pin mountings, while dispersing the stress and minimizing the strain transferred across the frame faces and flanges.  As with any frame bracket installation, Grade 8 flanged hardware is a must!

I have performed both modifications for the upper shock pin reinforcement at all four corners with complete success.  Patients and planning is key.  If you are interested and I have the opportunity, I will post pics.

Man if you could post some pics, that would be awesome.  Thank you!!

[Captkaos]

Ddi you see the image resize post.  On your phone if you are choosing max resolution they won't upload.  You have to resize them down. 800x600 is best in .jpg format

[jumbowolfe]

Did I post or upload a picture that was too big?  I'm confused?

[Irish_Alley]

if the picture is too big it wont let you post it. you can find apps on google play to change the size.
this is the one i use, it saves a new picture automatically once you select the resolution you want
Photo & Picture Resizer
https://play.google.com/store/apps/details?id=com.simplemobilephotoresizer&hl=en

[jumbowolfe]

I wasn't trying to post anything, I host my own anyway, I don't upload to the forum.  That's why I was confused.

[bd]

Pics of the left rear and right rear upper outer shock pin supports fabricated from 5/16" thick mild steel plate.  The concentric and starburst cracks propagating around and radiating outward from the shock pin holes were prepped, welded and repaired as previously described, before the mounts were measured and fabricated.  The original shock pin holes penetrating the frame rail were also reinforced with washers, again, as previously described.  Grade 8 flanged frame bolts extend through 5/16" backup plates mounted on the inside of the frame rail, so that the rail face is securely sandwiched between the outer supports and inner backup plates.  The edges of the backup plates facing the frame rail are gently beveled so as to relieve the development of stress risers during minor frame face flex.  Notice that the supports are cut to allow for shock fore and aft motion as the axle moves in six directions: up-down, fore-aft, side-to-side.  Although not obvious in the pics, clearances between the tops and sides of the shocks and support margins are more than adequate.  The supports are shaped differently from side-to-side, because of differences in the frame rails from side-to-side.

The 1/4" thick front upper outer shock supports mirror one another left-to-right and are similarly backed up by 1/4" plates inside the frame.  As with the rear, the backup plates are gently beveled to relieve the potential development of stress risers.  Grade 8 flanged frame bolts and nuts were also used for the front support mountings.

Fabrication of the supports was time consuming, because of the need to measure, and remeasure, and remeasure, before cutting and welding.  All welds were then burned from both sides to ensure full penetration and fusing of the steel.

[roundhouse]

Very nice!!

Wanna sell a few sets ?


Sent from my iPhone using Tapatalk

[LTZ C20]

Very nice!!

Wanna sell a few sets ?


Sent from my iPhone using Tapatalk

No seriously, I'm in too. You should consider patenting them, and then sell them on the site store if Chris would be into that idea. I don't have any frame issues with my truck so there for no reinforcements but these here I would get.

[nazielinski]

I would love to have a set the look really good too

Sent from my XT1254 using Tapatalk

[Don5]

I just saw a post on another site that shows ORD is now selling a rear shock brace for our trucks.   Here is an excerpt.

#GU38017  -  Rear shock brace for '73-'91 GM full size Blazers and Suburbans and '73-'87 1/2 and 3/4 ton pickups.  Installation requires aftermarket shock mount studs.  Does not fit K30's.

The rear shock mounts on '73-'87 ('91) Chevy trucks are set up in single shear and that makes them another spot in the frame that is failure prone.  To prevent the frame from cracking at the rear shock mount location, ORD created this kit to mount the rear shocks in double shear, spreading the load across more of the frame and helping prevent damage.  Installation of the ORD shock brace requires an aftermarket shock mounting stud (the stock "stud" is usually integral with the shock upper bushing).  If the shocks have been replaced in the past, they probably already have aftermarket type studs.  Aftermarket studs vary, so the holes in the ORD braces may have to be drilled larger to accept pre-existing aftermarket studs.  The ORD brace and stud work together without modification.

#GU38018  -  Replacement shock stud for '73-'87 ('91) Chevy truck

[jumbowolfe]

Excellent, thanks for posting that!