A/T - Drive Link Wear Specification Revised

90buick06
Bulletin: 90-7-3A

Date: Apr. '90

Ref. No.: 90-041A-7440

Corp. Ref. No.: 977158R

SUBJECT: REVISED DRIVE LINK WEAR SPECIFICATION


MODELS AFFECTED: ALL VEHICLES EQUIPPED WITH HYDRA-MATIC 3T40 (THM 125C) OR HYDRA-MATIC 4T60 (THM 440T4)


THIS BULLETIN SUPERSEDES BULLETIN 90-7-3. PLEASE DISCARD 90-7-3.

This bulletin has been revised to change the drive link specification information for the Hydra-Matic 4T60 (THM 440T4) transaxle. See "BULLETIN COVERS", "SERVICE PROCEDURE - Measure" and "SERVICE MANUAL REFERENCE". Also, "crayon" has been changed to "a pencil" under "SERVICE PROCEDURE - Inspect".

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 440T4) is 27.4 mm (1-1/16 in.).

Figure 1 - Checking Drive Link Wear:

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: 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 440T4), replace the drive link.
SERVICE MANUAL REFERENCE:

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