73-87 Chevy _ GMC Trucks > Projects Posts (NOT VEHICLES)
87 R10 Cracked Frame Repair @ Steering Gear
bd:
This thread is an afterthought, so not a consecutive record of images. No "before" pix, but suffice it to say, "It was awful!" The gearbox pivoted greater than one-half inch away from the framerail and was barely retained by two of its four mounting bolts. :o
The failure generally occurs as the steering gear pivots back-and-forth around an axis intersecting the top rear and lower front gearbox mounting bolts, tincanning the frame. Crack-out of the frame is always exaggerated around the top front and lower rear gearbox bolt holes. Interestingly enough, cracks propagate along nearly identical paths from vehicle-to-vehicle. Frame cracking around the steering gear mount is worsened by the installation of larger tires, because of the increased force transferred to the frame as the gearbox overcomes greater resistance and leverage caused by increases in width, diameter and mass of the steer tires.
I began by clamping the frame back into its original shape and position. Drilled 1/16" through holes at the end of every crack to keep them from propagating further. V-grooved the full length of each crack to a depth of ~1/8" (or ~2/3 of the way through the 3/16" frame). Tack welded the ends and intersections of the cracks, then welded each for full penetration. Cleaned the inside of the frame and welded the back side of each crack, then dressed the weld reinforcement down to the original surface to restore the frame's integrity and appearance.
Next step was to hammer form a Warrior Products #899 1/8"-thick frame reinforcement plate to exactly fit the contour of the framerail, and then coat the plate and the frame with weld-through primer. In addition, I fabricated and welded 1/8"-thick reinforcement onto the inside of the framerail around each of the four steering gear mount bolt holes.
bd:
Next step was to tightly clamp and weld the fishplate to the outside of the frame and weld a second reinforcement plate along the length of the framerail lower flange below the gearbox (part of the Warrior kit). Then I dressed it all down, primed and painted it.
I replaced the center crossmember, as well, since the PO used it as a tow hook and bent it beyond straightening.
bd:
Since I didn't want to revisit this failure in the future, I decided to address the cause of the tincanning and stabilize the steering gear mount. So, I fabricated torque arms for the steering gear mounting that rigidly bolt to the gear through the frame and anchor to the front crossmember at its center.
bd:
Torque arms installed...
sonicbluezx3:
Nice. How do you tell your frame is bent without removing the gear?
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