A/T - Drive Link Wear Specifications Revised

90chevy12
Number: 90-191-7A

Section: 7A

Date: March 1990

Corp. Bulletin No.: 977158
Subject: REVISED DRIVE LINK WEAR SPECIFICATIONS


Model and Year: 1984-90 A, J, L, T, X CARS AND 1990 W CAR AND U-VAN WITH 3T40 (125C) AUTOMATIC TRANSMISSION 1984-90 A CAR AND 1990 W CAR WITH 4T60 (440-T4) AUTOMATIC TRANSMISSION
THIS BULLETIN CANCELS AND SUPERSEDES DEALER SERVICE BULLETIN NO. 90-95-7A, DATED NOVEMBER 1989. THE DRIVE LINK SPECIFICATIONS HAVE BEEN CHANGED FOR THE 4T60 TRANSMISSION. ALL COPIES OF 90-95-7A SHOULD BE DISCARDED.

This bulletin covers the drive link wear specification has been changed to minimize noise. The previous specification for the HYDRA-MATIC 3T40 (THM 125C) was 27.4 mm (1-1/16 in.). The new specification is 22.2 mm (7/8 in.). The specification for the HYDRA-MATIC 4T60 (THM 440-T4) is 27.4 mm (1-1/16 in.).

SERVICE PROCEDURE: (Figure 1)

IMPORTANT: Make sure the three machined surfaces indicated in Figure 1 are flush with the machined surface of the case; if not, drive link measurement will be inaccurate.

Inspect:

Figure 1:

1) Midway between the sprockets and at right angles to drive link, with light pressure push the slack strand (bottom strand) of the drive link until all slack is removed, and mark the case with a pencil on the bottom side of the drive link. See Figure 1.

2) Push up in the same manner and put a second mark on the case, making sure that both marks are made from the same point on the drive link.

Measure:

The distance between the two marks. If the distance exceeds 22.2 mm (7/8 in.) for the HYDRA-MATIC 3T40 (THM 125C) or 27.4 mm (1-1/16 in.) for the HYDRA-MATIC 4T60 (THM 440-T4), replace the drive link.
SERVICE MANUAL REFERENCE:

Please make note of these correct procedures in your 1985 through 1990 Service Manuals.