K 2500 Truck 4WD V8-379 6.2L DSL VIN C FI (1989)
or 4th clutch pressure taps. The case bosses will be removed through normal die maintenance.
Service Action
Even though individual clutch pressure readings are no longer available, use of basic diagnostic procedures, as outlined in the Service Manuals, will
result in successful diagnosis of an automatic transmission concern. The first step in systematic transmission diagnosis is to obtain a complete description
of the condition from the vehicle owner. Gather as much information from the owner as they can provide. As an example, under what driving situations
does the condition occur, whether the condition is more noticeable when the vehicle is hot or cold, or in what gear range does the condition become
evident. Before driving the vehicle, check that proper fluid level and correct T.V. cable setting have been maintained. Check minimum and maximum
mainline pressures against the transmission pressure charts updated and printed each year in the appropriate Service Manuals. Also, one of the
preliminary checks should include making certain that the engine is in proper tune and not contributing to or mistaken for a transmission condition.
Figure 3 - Range Reference chart
With all preliminary information collected, the vehicle should then be road tested. During the road test, note when and in what range the condition
occurs. By comparing this information with the range reference chart (refer to Figure 3) you can begin to eliminate known good circuits and/or clutches.
Through this process of elimination, it is possible to pinpoint the circuit and/or clutch that is causing the condition.
