1996/06/03 Caterpillar

Field Repair For Cracked Upper Strut Mount Plate{7051}

Usage:

773B (63W) Truck

SUPPLEMENT: 02/17/97

Service Magazine; June 3, 1996; Pages 10-12; "Field Repair For Cracked Upper Strut Mount Plate" for 773B (63W) Trucks.

In Paragraph 3 replace "The plate is to be made of 1E0170 Steel or its equivalent (see approved substitute materials for 1E0170 Steel)." with the following sentence:

The plate is to be made of the approved materials provided below.

Also, replace the title "Approved Substitute Materials For 1E0170 Steel" with:

Approved Materials For Fabrication Of Plate

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SUPPLEMENT: 07/08/96

Service Magazine; June 3, 1996; Page 10; "Field Repair For Cracked Upper Strut Mount Plate" for 773B (63W) Trucks.

This service magazine article is also applicable to 775B (7XJ) Quarry Trucks.

The following should be added:

Field repair for cracked upper strut mount plate should also be completed on the 775B (7XJ200-Up) Quarry Trucks.

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Field repair can be performed for cracked upper strut mount plate. Welding the doubler plate in place strengthens the area and prevents further crack propagation.

Field repair for cracked upper strut mount plate can be performed by the following procedure for the new configuration of 773B (63W4200-Up) Trucks without rear gussets, built after May 1994.

1. Inspect the frame area to be sure that the only cracking is in the rear plate of the upper strut mount (Illustration 1). If cracking has propagated into the weld joint, be sure to repair the weld joint first by arcing out all of the crack and rewelding.

Illustration 1. Typical right-hand (RH) rear view of upper strut mount plate.

Upper horizontal fore-aft beam (1), weld joint (2), crack at inside of rear plate (3), rear plate of upper strut mount (4) and front strut casting (5).

2. Arc out the crack in the rear mount plate and repair, making sure to remove all of the crack (Illustration 2).

Illustration 2. View of crack location on the upper strut mount.

Arc out the entire crack (3) and weld plate. This can be done by arcing through half the thickness of the plate and welding. Arc out the crack and some of the new weld from the opposite side and weld up the crack. Grind to smoothen the weld repair surface (1), and grind to smoothen edge (2).

3. Make a doubler plate using the dimensions provided in Illustration 3. Grind the 55.0 mm (2.16 in) radius smooth to eliminate any marks created from burning out the plate (if possible, a machined surface finish would be best in the area of the 55 mm (2.165 in) radius). The plate is to be made of 1E0170 Steel or its equivalent (see approved substitute materials for 1E0170 Steel). Place the doubler plate at the back of the rear plate for the upper strut mount locating it toward the inside of the truck (Illustration 5). Weld the doubler plate to the rear mount plate making sure to weld all the way around.