Checking Transmission Operation; General Checks; Transmission Fluid Level; Check Atf Level - Porsche 928 Workshop Manual

38
Automatic Transmission/Gears, Valve Body
928
CHECKING TRANSMISSION OPERATION
Prior to making repairs on an automatic trans,
mission, troubleshoot transmission as
instructed below and with help from the
following tests.
A - General Checks
8 - Transmission Fluid Level
C - Stall Speed
D - Test Drive
E - Pressure Test
Caution!
All jobs, which require that engine runs,
should only be carried out with selector lever
in "N" or "P" and parking brake applied.
Exceptions are tests, which require briefly a
different selector lever Dosition.
A- General Checks
Following jobs must be performed prior to
any testing of transmission, and if defects are
found, they must be eliminated before con-
tinuing with other work on transmission.
1. Check engine tuning (ignition timing, idle
and transition).
2. Check for external damage, e. g. leaks on
transmission (ATF) or final drive (hypoid
oil) and missing or loose mounting bolts.
B-Transmission Fluid Level
The specified fluid level is extremely
important for proper operation of an
automatic transmission, so that following
test must be carried out with great care.
Check ATF Level
Also check appearance and odor of ATF.
Burnt friction linings cause a burnt odor.
Contaminated oil could cause failure in valve
body.
In this case transmission must be removed
and repaired or replaced. ATF lines and
cooler must also be flushed.
ATF level check is carried out at engine idle
speed, parking brake applied and selector
lever at "N". Car must be on level surface.
Let engine run at idle speed 1 to 2 minutes
before checking fluid level, so that torque
converter will be full.
ATF level can be checked on a cold or
warm transmisstion. However, the level will
be more accurate on a cold transmission
(20 to 3O"C/68 to 86°F ATF temperature)
than on a warm transmission (8O"C/176"F
ATF temperature). ATF temperature of
8O"C/176"F can only be estimated.
38. 102
Checking Transmission Operation
Printed in Germany