Spicer Tandem Drive Axles Service Manual D__R440, 460, 480, D_R461, 462, 463, 521, 581, 601, 651, 652, 653 - Manual (Page 94)

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Wheel Differential Lock
Lubrication
Lubricant: Use SAE 10 motor oil* for temperature above 0°F
(–18°C). For temperatures below 0°F (–18°C), mix three parts
of SAE 10 motor oil with one part of kerosene. This cold weath-
er mixture can be safely used up to 32°F (0°C).
Note: Commercially available automatic transmission fluid
may be used in place of SAE 10 motor oil. Automatic
transmission fluid can be used for all temperatures. Do
not mix kerosene with automatic transmission fluid.
Lubricant Check and Level: Each 20,000 miles or six months,
remove pipe plug in shift unit housing cover to check lubricant
level. Lube should be level with bottom of filler hole [1.5 oz.
(50 ml)].
Lubricant Change: At least once a year remove shift unit hous-
ing cover and drain old lubricant. Wash parts thoroughly and
air dry. Reinstall cover. Remove pipe plug in cover. Fill through
pipe plug opening until lube is level with bottom of filler hole.