Greetings folks,
With the purchase of my
truck came a complete
2 speed differential from the truck's 17,000# axle. Apparently the previous owner (or owner before him) had to replace it for some undisclosed reason. I suspect that perhaps the replacement itself wasn't installed correctly given the
troubles I\'ve been having. .
Nonetheless, I decided to take it apart and perform a failure analysis in order to determine the cause of failure that warranted replacement. This merely involved taking the differential apart, cleaning the pieces and looking for obvious signs of failure such as broken components, excessive wear, thermal damage, etc.
The removal of all the components was fairly straightforward, though I sure am glad I bought that 24 piece 3/4" socket set. Everything is big on a C60
. Each piece was cleaned in my parts tank as it came off. I found the major components (yoke, drive pinion gear, ring gear, shifter sleeve and yoke, bearings and races) to actually be in great shape given their age and the fact that it's a 2 ton truck.
Next I unbolted the ring gear from the Differential and Planet Support Case and Ring Gear and split open the case to reveal the
sun and planetary gears .
The first sign of trouble came in the form of thermal damage to the Differential and Planet Support Case and Ring Gear. Note the
bluish thermally induced discoloration on the inside walls of the case. Additional thermal damage was found on the top and base area of each of the 4
differential pinion gear posts , again evidenced by the bluish thermally induced discoloration.
The
differential was then disassembled piece by piece and each component was cleaned and inspected.
Excessive scoring was noted on the inside of the 2 halves of the Differential and Planet Support Covers. Further examination revealed scoring and galling of the
spider shafts and differential pinion thrust washers .
This truck has a 22,000 lb. GVWR. Inspection of the frame and undercarriage prior to purchase revealed no obvious signs of abuse (cracks in the frame of leaf spring hangers, sagging springs due to fatigue, frame twist, etc.). Therefore, the thermal stresses must have been caused either by using an improperly rated lubricant or by an insufficient quantity of lubricant. In addition to the obvious property of lubrication, gear oil also dissipates heat from the metal components. The damage observed here suggests that there was an inadequate quantity of gear oil in the differential case, thus leading to the thermal damage on the inside of the differential.
All of the picture that I took during this process can here found
here .
It's unfortunate that improper maintenance likely led to the failure of this differential. Aside from the damage to the inside of the differential, the rest of the 2 speed components are actually in great shape.
Hopefully folks will find this informative and interesting.
Thanks, in advance!!!
