Background

Throttle valve (T.V.) pressure controls the shift pattern and the amount of hydraulic line pressure used to apply clutches and bands. (NOTE: The THM 440-T4 T.V. cable controls shift timing, not shift feel, line pressure is not directly affected by T.V. cable setting.). If proper line pressure is not available, excess slippage may occur during the shift. If the T.V. cable is tailored in an effort to modify shift pattern/feel, this misadjustment can result in transmission/transaxle failure.

IMPORTANT: Do not attempt to correct a condition by changing the T.V. cable setting from its proper adjustment. Apparent improvements from T.V. cable "tailoring" indicate a need for further diagnosis into the real cause of a condition (such as engine performance, the control valve, governor or servo assemblies, etc.).
Dealer personnel and customers should know that certain types of heavy duty or high performance vehicles have transmissions calibrated to provide crisp, firm shifts for durability/performance. Once again, the T.V. cable must not be tailored in an effort to modify shift pattern/feel on these applications.

IMPORTANT: Make sure engine fuel, electrical and mechanical systems are performing properly before attempting transmission/transaxle diagnosis. For example, a fouled fuel injector, cracked spark plug, damaged spark plug wire or vacuum leak can affect transmission/transaxle performance.

The T.V. system may cause one or more of the following conditions:

-- Delayed or harsh upshifts
-- Early and slipping upshifts
-- High or low line pressure (except the THM 440-T4)
-- No upshifts
-- Chatters on takeoff
-- 1-2 shift at full throttle only
-- No full throttle or part throttle detent downshifts
-- Intermittent second gear starts

The above listed conditions may be caused by a T.V. cable that is:

-- Improperly adjusted
-- Kinked or binding
-- Disconnected
-- Broken
-- Wrong part

CAUTION: To avoid possible personal injury and/or damage to the vehicle, the following diagnosis procedure must be performed with the vehicle parking brake properly applied.