Unnecessary Testing Of Modulating Pressure (27/89)

Publication date: 1991-03-01
Reference number: 27/89

UNNECESSARY TESTING OF MODULATING PRESSURE

TECHNICAL SERVICE BULLETIN

Reference Number(s): 27/89, Date of Issue: March 1991

ALL MODELS WITH AUTOMATIC TRANSMISSION - UNNECESSARY TESTING OF THE MODULATING PRESSURE

Model(s): All Mercedes-Benz Models

Group: 27 - Automatic Transmission

Bulletin No.: 27/89

Date: March 1991

SERVICE INFORMATION

In cases of customer complaints of "poor automatic transmission performance", the modulating pressure test should only be carried out in the following circumstances:

Up-shift too hard or too soft in all gears (poor shift quality while driving).
NOTE: On diesel vehicles the vacuum line must be in good condition, properly routed and the vacuum control valve in proper working order.
After R & R of the vacuum modulator.
After a transmission repair in which the vacuum modulator was removed and/or the clutch plates or brake bands were burned (dark in appearance) and replaced.

The modulating pressure test is not required in case of:

Hard engagement into "D" or "R".
No up-shift.
Deviations from individual shift points.

Future warranty claims in which the modulating pressure was checked, in any of the above cases, will be reviewed more carefully.