Usage:
768C, 772B, 776 Tractors;
769C, 773B, 777 Trucks
Reference: See the article, "Changes Made To Brake Lines and Brake Oil Cooler Lines" in this Service Magazine.
Description of Change: Improvements have been made to the main frames of the above models.
Four reinforcement plates have been added to the rail assemblies where the rear support assembly is connected. See Illustration 1. Use of the reinforcement plates has the same effect as if the rear support assembly were extended further into the rail assemblies. The result is a stronger connection.
During fabrication, the reinforcement plates are installed through openings in the inner sides of the rail assemblies. Plates are then welded to the rail assemblies to close the openings.
The rear support assembly for 768C and 772B Tractors and 769C and 773B Trucks has been strengthened. See Illustration 2. Two reinforcement plates and some internal welds, similar in design to those used on all 776 Tractors and 777 Trucks, have been added.
Illustration 1. Locations of the reinforcement plates.
Illustration 2. Improved reinforcement in rear support assembly.
Full-length internal welds are used at the junctions between the back plate and both the top and the bottom plates. The internal welds were added at the front plate, but they are not full length; there are no welds on the front plate between the reinforcement plates.
The reinforcement plates were added in alignment with the tow pin bracket. The result is a stronger area near the tow pin.
Several other-improvements have been made to the main frame for 768C Tractors and 769C Trucks.
Eight reinforcement plates have been used in the frame rail assemblies since first production of the "C" Series Trucks. Four of the plates are used where the brackets on the center support assembly connect to the rail assemblies. See Illustration 1. The plates, which give added support for welds between the brackets and rail assemblies, have been improved.
The rail assemblies use a support (reinforcement plate) of an improved design. See Illustration 3. A support has been used since first production of 768C Tractors and of 769C Trucks. The original support was flat. The new support has a radius like the rail, and it ends have tapers. Because of the radius, the new support has increased contact surface with the rail. The taper ends give more weld area to prevent cracks. The result is a stronger rail assembly.
Illustration 3. Location of improved support in rail assembly.
Three improvements have been made with the center support assembly. See Illustration 4. Improved welds are used to connect the support for the rear axle housing to the center support assembly. A different assembly procedure permits access to make the welds with better penetration. The support assembly has larger plates for the hoist cylinder brackets. Also, the plates go all the way around the center tube. The end brackets for the center support assembly have larger openings. These larger openings permit internal welds to be added between the brackets and the center tube.
Adaptable To: The improvements are in effect on machines with Serial Numbers 1X1650, 2X327, 63W569, 64W152, 84A675 and 14H148. Because conversion is difficult and because many of the parts are not available for service, no procedure or parts list is given for installation on earlier trucks.
If main frame repairs are necessary, contact your Division Service Manager.
Illustration 4. Improvements to the center support assembly.