Testing During the Road Test

NOTE:
The test methods described below are used to check the normal functions of the automatic transmission. Judging the operation and troubles, if any, of a transmission, obviously requires experience in handling automatic transmissions. Without such experience it will be of advantage to use another automatic transmission which is still in good order and of the same design for making comparisons. If the test shows irregular functions. reference to "Programmed repairs" will assist in finding the causes of such faults.

Prior to starting, be sure to check the oil level, the idling speed of the engine, and adjustment of control pressure cable control.

During test make sure that the gears are not continuously changed, particularly under load. While changing gears, considerable heat is generated at the servo members. Reference value: Repeat a load change only once within 15 seconds.

Test Drive
During test drive, in addition to shiftpoints, special attention should be paid to changeover during gear change.

Shifting up at part throttle should be noticed only when listening carefully. At full throttle and kickdown the gear changes are clearly heard but the new gear speed should obtain a smooth hold and the impression of an energetically pullinq engine should remain. Sudden revving up of the engine, for example, when shifting up indicates the slipping of a servo member (brake band or clutch) and should be checked.

Automatic downshifts without applying the throttle occur at very low speeds and will be heard only when listening very carefully (speed increase of engine). On the other hand, downshifts under kickdown are coupled with a clearly felt shifting impulse in addition to an increase in engine speed. At certain speed ranges a downshift under part to full throttle is possible.

Downshifts with the selector lever are either downshifts while applying the throttle (for example uphill) or decelerating shifts without applying the throttle (for example downhill or when decelerating). Downshifts while applying the throttle require only a few fractions of a second for changing gears, while decelerating shifts with-out applying the throttle require from 1 to 2 seconds.