A/T - THM 700-R4/4L60 Stuck In First Gear

91cadillac07

Bulletin No. T-91-102
File in Group 7
Number 234
Corp. Ref. No. 177113R
Date July, 1991


SUBJECT: TRANSMISSION STUCK IN FIRST GEAR (INSTALL INPUT CARRIER TO OUTPUT SHAFT RETAINING RING)

MODELS AFFECTED: 1990-1991 BROUGHAMS WITH HYDRA-MATIC 4L60 (THM 700-R4) TRANSMISSION

Figure 1:

Some 1990-1991 Broughams with the Hydra-Matic 4L60 (THM 700-R4) transmission may experience a "no upshift" or "stuck in first gear" condition. This condition may be caused by the input carrier to output shaft retaining ring becoming unseated or being missing (item 661 in Figure 1). This can allow the output shaft to move and cause wear on the governor driven gear (THE GEAR ON THE GOVERNOR). The governor gear wear is usually described as an "apple cored" condition. If the governor cannot rotate due to gear wear, the transmission cannot upshift out of first gear.


To diagnose and repair this condition, remove the governor and inspect the governor driven gear. If the governor driven gear is OK, refer to Diagnosis Chart B, "1st GEAR RANGE ONLY - NO UPSHIFT" in Section 4L60 Hydraulic Diagnosis in the appropriate Service Information Manual. If it is "apple cored", remove and disassemble the transmission and look for the presence of the input carrier to output shaft retaining ring.

^ If the retaining ring is missing, replace it and make sure the original retaining ring is not broken and stuck inside of the transmission.

^ If the retaining ring has become unseated, replace the retaining ring with a new one, since the original has probably over-expanded.


^ If the retaining ring is present and seated, inspect the governor drive gear (THE GEAR ON THE OUTPUT SHAFT) for being located and retained properly. Repair as necessary.

IMPORTANT: When installing a new retaining ring, be careful not to over-expand the retaining ring.

The input carrier to output shaft retaining ring is available in several packages through GMSPO. It is included in the snap ring package, overhaul repair components package, and the overhaul seals and gaskets package. Refer to the appropriate Service Parts Catalog for package part numbers.

Refer to the appropriate Service Information Manual for on-vehicle and unit repair information.