Towing Vehicle Tips
Road Test Tips
Testing during the road test
 

Note

The normal functions of the automatic transmission can be checked using the test procedure described. Assessment of the function and any faults in the transmission naturally requires experience with automatic transmissions. If such experience is not available, it is advisable to obtain another automatic transmission of the same type and in perfect working order for comparison. Should the test reveal irregularities, the causes of any faults detected can be found with the aid of the "Programmed repairs".

Before beginning the test, always check the oil level in the transmission, the idle speed of the engine and the adjustment of the control pressure cable.

Road test
Besides the shift points, the road test must include a check of the transitions when changing gear.

In the part-load range, the upshifts should be such that they are only perceptible when particular attention is paid to them. At full throttle and kickdown, gear changes are clearly perceptible, but the new gear should still engage smoothly and not impair the impression of the engine's powerful pull-through.

For example, any sudden revving of the engine during upshiffing indicates slippage of a servoelement (brake band or clutch) and must be examined in more detafl. Automatic downshift with no throftle occur at extremely low speeds and are only perceptible when particular attention is paid to them (the engine speed increases). In contrast, downshifts under kickdown conditions involve both an increase in engine speed and a clearly perceptible jolt when shifting. In certain speed ranges, it is possible to downshift with part to full throttle.

Downshifts perfonned with the selector lever are either downshifts; with throttle (e.g. uphill) or brake shifts without throttle (e.g. downhill or when decelerating). Downshifts with throttle require only a few fractions of a second for the gear change, whillst brake shifts without throttle last between 1 and 2 seconds.

In driving position "2", the upshifl: in vehicles with 6-cylinder engines only occurs just before the maximum engine speed is reached.

During the test, ensure that the transmission is not shifted continually, particularly when under load. The shifting process generates substantial heat at the servoelements. As a reference: Repeat a gear shift under load once only within 15 seconds.

 

 
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