A/T - Checking for Possible Lack of Lubrication

Number: 83-I-86

Section: VIIc

Date: June, 1983
Subject: PROCEDURE TO CHECK FOR POSSIBLE LACK OF LUBRICATION - THM 700-R4

TO: ALL CHEVROLET DEALERS

When overhauling a THM 700-R4 transmission which shows signs of high oil temperature (such as burned transmission fluid, parts turned a blue color, etc.) be certain to check the lubrication passages as follows:

1. Flush the oil cooler and cooler lines as shown in Section 7A of the 1983 Service Manual.

FIGURE 1 - PUMP COVER LUBE CHANNELS:

FIGURE 2 - CASE LUBE CHANNELS:

2. Air check the lubrication passages in the case and oil pump cover (see Figures 1 and 2).

FIGURE 3 - INPUT HOUSING LUBE CHANNEL:

FIGURE 4 - INPUT CLUTCH HOUSING:

3. Air check the lubrication passage in the input housing (see Figures 3 and 4). Check the input housing to output shaft lip seal for wear or damage. Replace with P/N 8642178 if necessary (see Figure 4).

FIGURE 5 - OUTPUT SHAFT CROSS SECTION:

4. Flush and air check the lubrication passages in the output shaft (see Figure 5).
When replacing the converter assembly or any internal parts which shows signs of high temperature such as a blue color, be certain to find and correct the restriction in the lubrication circuit which feeds that part. However, do not confuse a wear pattern with lack of lubrication (i.e. a worn thrust washer or any part which shows a localized heat pattern is not generally caused by lack of lubrication. Whereas if the part is completely turned blue, this indicates lack of lubrication.) Any example of a localized heat pattern is a blue color around a pinion pin (or pins) in the input or reaction carrier. A blue color around these pins is generally caused by worn pinion washers or *keystoned pinion needle bearing rollers, not lack of lubrication.

An important point to remember on the THM 700-R4 (or any THM automatic overdrive transmission) is that the converter clutch

must be functioning when the vehicle is driven in fourth gear or above normal oil temperatures can result. The higher oil temperatures may cause wear of the transmission parts and should not be confused with lack of lubrication. Above normal transmission oil temperatures can result in deterioration of the oils lubricity.

*Keystoned needle bearing rollers means - the rollers are wedged together by twisting each end of the rollers in opposite directions. This procedure is used to retain the rollers inside the pinion gear during assembly. After assembly is complete a gentle tap will loosen the keystone and allow the pinion gears to turn freely.