Transfer Case - Shift Effort High in Cold Temperatures
90chevy34GMC NUMBER: 90-7D-112
GROUP: 7D Transfer Case
DATE: December, 1990
CORPORATE
NUMBER: 967402R
SUBJECT: HIGH TRANSFER CASE SHIFT EFFORT
MODELS: 1988-90 K1, K2, K3 AND 1983-91 T1 LIGHT DUTY TRUCKS
THIS BULLETIN CANCELS AND REPLACES GMC TRUCK SERVICE BULLETIN 89-T-90 DATED AUGUST 1989 TO ADD 1990 K MODELS AND 1983-91 T MODELS AND TO REFLECT THE AVAILABILITY OF
SYNTHETIC 75W-90 GEAR LUBE IN ONE QUART BOTTLES FROM GMSPO.
Some four wheel drive K and T trucks may experience high transfer case shift effort and/or total blockouts when "SHIFTING ON THE FLY" from 2H to 4H under cold weather conditions (usually 25 degrees or less). In order to shift to 4H the speed of the front propshaft must be increased to allow proper engagement of front axle. As the transfer case shift lever is moved into 4H the front propshaft begins rotating to synchronize the front axle assembly. In cold weather conditions regular production lube has high viscosity which may delay or prohibit the synchronizing of the front propshaft and axle resulting in high transfer case shift effort. To reduce high shift effort, regular production front axle gear lube may be replaced with a 75W-90 synthetic gear lube which maintains a lower viscosity under cold weather conditions. This synthetic gear lube is now available in one quart containers from GMSPO. Before installing, it is important to drain and flush the front axle with clean mineral based (non-synthetic) axle lube. The front axle should then be refilled to the level of the filler hole.
Front Axle Lube Capacities:
K1, K2 1.66 liter (1.75 qts)
K3 2.13 Liter (2.2 qts)
T1 1.20 liter (1.3 qts)
SERVICE PARTS INFORMATION
P/N DESCRIPTION
12345836 SAE 75W-90 synthetic gear
1 qt. bottle
Parts are currently available from GMSPO.
WARRANTY INFORMATION For vehicles repaired under warranty use:
Labor Operation: T7980
Labor Time: .4 hr
NOTE: Labor Operation is coded to base vehicle coverage in the warranty system.