ERRATIC/NO UPSHIFTS/THM 700 R4 DIAG. WORN GOV. GEAR. GMC Truck S15 Pickup - 4WD 1983

For 1990-2009 cars

# ERRATIC/NO UPSHIFTS/THM 700 R4 DIAG. WORN GOV. GEAR

#### MODELS: LIGHT DUTY TRUCKS WITH THM 700-R4 TRANSMISSION

In diagnosing any THM 700-R4 transmissions for erratic or no upshifts, the cause may be from a worn governor gear. The cause of the worn governor gear may be from one or more of the following conditions:

1. The output shaft to input carrier assembly snap ring came off.

2. Metal scale on the output shaft gear.

3. The governor dowel pin dimension may be incorrect.

4. An incorrect governor gear may have been installed.

When servicing any THM 700-R4 transmission for an erratic or no upshift condition, refer to the following diagnosis chart:

Follow guidelines given in your service manual for servicing the transmission governor gear.

Condition Cause Correction --------- ----- ----------

A. Governor Gear is 1. Flash, scale or nicks on 1. Replace governor gear worn in an "Apple the output shaft gear. (Part no. 8642928) Core" shape (Refer 2. Incorrect governor gear wire brush output to Figure No. 1) (THM 350-C type) shaft gear to remove scale of flash. Replace output shaft if nicked.

2. Replace governor gear (part no. 8642928). Do not use THM-350C type as replacement.

B. Governor gear 1. The governor dowel 1. Replace the trans- is worn in the pin is located too mission case. Check middle, but on far into its case replacement case for one side only bore. (Refer to correct dimension. (Refer to Figure No. 3 for Figure No. 2). correct dimension. 2. Replace governor assembly and trans- 2. Governor sleeve stuck mission case. in case bore. 3. Dissasemble the 3. The output shaft to transmission, replace input carrier snap ring the output shaft to is loose or has come input carrier snap off. The output ring. (Part No. shaft has moved rear- 8642230). ward.

C. Governor Gear is The governor dowel pin Arbor press the dowel worn at the edge of is located too far out pin into the case to the eear on one of its case bore.(See correct dimension side only (refer Figure No. 3 for correct (Refer to Figure to Figure No. 4) dimension.) No. 3)

D. Governor gear is The incorrect governor Replace the governor worn slightly, the gear was installed. gear (Part No. entire length of 8642928) Do Not Use the gear. (Refer A THM 350-C gear as to Figure No. 5). a replacement gear.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.