A/T - THM 700-R4 Erratic or No Upshifts

Number: 84-13

Section: 7A (VIIc)

Date: Oct., 1983
Subject: ERRATIC OR NO UPSHIFTS


Model and Year: THM 700-R4
TO: ALL CHEVROLET DEALERS

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.

FIGURE 1 - GEAR WEAR "APPLECORED":

CONDITION CAUSE CORRECTION

1. Governor gear 1. Flash, scale or 1. Replace governor is worn in an nicks on the gear (P/N "Apple Core" output shaft 8642928) wire
shape (refer gear. brush output
to Figure 1). shaft gear to
2. Incorrect goverremove scale of nor gear (THM flash. Replace 350C type). output shaft if
nicked.

2. Replace governor gear (P/N 8642928). Do not use THM 350C type as replacement.

FIGURE 2 - GEAR WEAR IN THE MIDDLE, ON ONE SIDE ONLY:

FIGURE 3 - GOV. DOWEL PIN DIMENSION:

CONDITION CAUSE CORRECTION


2. Governor gear is 1. The governor dowel 1. Replace the transworn in the middle pin is located too mission case.
but on one side far into its case Check replacement
only (refer to bore. (Refer to case for correct
Figure 2). Figure 3 for cor- dimension.
rect dimension.)

2. Governor sleeve 2. Replace governor stuck in case bore. assembly and transmission case.
3. The output shaft to input carrier snap 3. Disassemble the
ring is loose or transmission, re-
has come off. The place the output
output shaft has shaft to input
moved rearward. carrier snap ring.
(P/N 8642230).

FIGURE 4 - GEAR WEAR ON THE BOTTOM EDGE ONE SIDE ONLY:

FIGURE 5 - SLIGHT GEAR WEAR IN THE MIDDLE THE ENTIRE LENGTH OF THE GEAR:

3. Governor gear is The governor dowel Arbor press the worn at the edge pin is located too dowel pin into the
of the gear on one far out of its case case to the correct
side only (refer bore. (See Figure 3 dimension. (Refer
to Figure 4). for correct dimen- to Figure 3).
sion.)


4. Governor gear is 1. The incorrect gover- 1. Replace the goverworn slightly, nor gear was innor gear (P/N the entire length stalled. 8642928). Do not
of the gear. (Re- use a THM 350C gear
fer to Figure 5). as a replacement
gear.