M/T - No 4th Gear or Hard Shift Into 4th Gear
88chevy03
GMC NUMBER: 88-T-75
GROUP: 7B - Manual Transmission
DATE: January, 1988
CORPORATE
NUMBER: 877206
SUBJECT: NO 4TH GEAR OR HARD SHIFT INTO 4TH
MODELS: 1988 C/K MODELS EQUIPPED WITH HM-290 4-SPEED (RPO MCO) OR 5-SPEED (RPO MG5) MANUAL TRANSMISSIONS
FIGURE 1 - NEW "WING" DESIGN SYNCHRONIZER KEY:
BULLETIN COVERS:
Some 1988 C/K trucks equipped with a HM- 290 4 or 5-speed manual transmission may exhibit a no 4th gear or hard shift into 4th gear (4TH GEAR ONLY). This condition may be caused by a key cocking in the 3-4 synchronizer assembly. To correct the condition, install the service parts package that contains new "wing" design synchronizer keys (Figure No. 1).
FIGURE 2 - HM-290 TRANSMISSION IDENTIFICATION INFORMATION RPO MCO/MG5:
DATE OF PRODUCTION CHANGE: (Figure No. 2)
Starting November 13, 1987 new "wing" design synchronizer keys that prevent cocking are used in only the 3-4 synchronizer assembly. At a later date, the new keys will be used in the 1-2 and the 5th-Reverse synchronizer assemblies.
SERVICE ACTION:
Install the service part packages listed below.
SERVICE PARTS INFORMATION:
Package No. Qty. Package Description
1052931 2 Manual Transmission
Fluid (1 Qt.) .946L
8672936 1 HM-290 Overhaul Kit
8672050 2 Synchronizer Rings (2)
8672927 1 3-4 Hub Selective Snap
Ring Set (6)
23049729 1 Synchronizer
Assembly, 3-4 (7) Includes:
1 Synchronizer Sleeve (8)
3 Synchronizer Detent
Ball (9)
3 Synchronizer Detent
Spring (10)
3 Synchronizer Key,
("wing" design) (11)
1 Synchronizer Hub (12)
NOTE: Inspect the 3-4 synchronizer assembly prior to installation to make sure that it was built with the new "wing" design synchronizer keys.
SERVICE MANUAL REFERENCE:
Refer to section 7B1 of the 1988 Light Duty Truck Unit Repair Manual for procedures.
LABOR TIME INFORMATION:
0w se K2700: Transmission Assembly - Recondition C-Truck..........................2.0 Hrs. K-Truck .........................2.2 Hrs.
ADD: A-W/Skid Plate (If K-Truck is equipped with one).............................0.3 Hr.
ADD: I-Reconditioned Mainshaft (4sp/5sp) ............................1.7 Hrs.