M/T - No 4th Gear or Hard Shift Into 4th
88chevy12REISSUE
Number: 88-143-7BR
Section: 7B
Date: Feb., 1988
Subject: NO 4TH GEAR OR HARD SHIFT INTO 4TH
Model and Year: 1988 C/K TRUCKS WITH HM 290 MANUAL
TRANSMISSION, (RPO MCO, MG5)
TO: ALL CHEVROLET DEALERS
This bulletin is being reissued to correct the part number listed for the manual transmission fluid. All copies of 88-143-7B dated February 1988 should be discarded.
FIGURE 1 - NEW "WING" DESIGN SYNCHRONIZER KEY:
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 1).
FIGURE 2 - HM-290 TRANSMISSION IDENTIFICATION INFORMATION RPO MCO/MG5:
Starting November 13, 1987 (Figure 2) new "wing" design synchronizer keys that prevents 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 PARTS INFORMATION:
Package No. Package Description
1052931 (2) Manual Transmission Fluid (1 Qt). .946L
8672936 (1) HM 290 Overhaul Kit
8672050 (2) Synchronizer Rings (2)
8672927 (1) 2-4 Hub Selective Snap Ring Set (6)
23049729 (1) Synchronizer Assembly, 3-4 (7)
(1) Synchronizer Sleeve (8)
(3) Synchronizer Detent Ball (9)
(3) Synchronizer Detent Spring (10)
(3) Synchronizer Key, ("wing" design) (11)
(1) Synchron 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.
LABOR TIME INFORMATION:
Labor Operation: K2700
Labor Time: C Truck 2.0
K Truck 2.3
ADD: A w/shield plate .3 (K Truck)
I Recondition Mainshaft 2.0
(4 sp/ 5 sp)