Article 1273 - High Shift Efforts and Noise

TSB #85 - February 9, 1968
(All Trucks Equipped with all 5 Speed Transmissions - Spicer, Fuller, Clark, New Process)


Poor preventative maintenance can contribute to all 5 speed transmission (Clark, Spicer, Fuller, New Process) problems. The following is the suggested proper preventative maintenance as related to transmission lubricant and "C series shift linkage.

Transmission Lubricant:
To insure proper lubrication and operating temperatures, it is important that proper lubricants be used and correct oil levels be maintained in transmission. For temperatures above 10°F, Heavy Duty Engine Oil SAE 50 is recommended. For temperatures below 10°F Heavy Duty Engine Oil SAE 30 is recommended. The API service classification of this lubricating oil can be MS, DG, DM, or DS. Lubricants with (EP) additives, such as multi-purpose lubricants, should not be used. Extreme pressure lubricants have a tendency to break down, form sludge and varnish which can contribute to a hard shifting complaint.

Transmissions should be drained and refilled at 12,000 mile intervals (off road at 8,000 mile intervals). Lubricant should be added to the transmission until the lubricant level is to the bottom of the filler hole.

"C" Series Shift Linkage:
Failure to properly lubricate the "C" series shift linkage also contributes to increased transmission shifting problems. Lack of lubrication between slip joint and the shift lever can result in a complaint of hard shifting out of reverse, second, or fourth gears. It is also possible to inadvertently overlook the slip joint zerk fitting while lubricating the vehicle. The shift linkage should be lubricated with C1AZ-19590-B,C,D, or E grease. The normal maintenance interval for the "C" series vehicle is 4,000 miles.