Porsche 928 Workshop Manual page 800

928 Automatic Transmission / Gears, Valve Body
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TROUBLESHOOTING AUTOMATIC TRANSMISSION
Note: If transmission oil is black and smells burnt or there is an
unusual large amount of metal burrs in oil pan. either
repair 01 replace transmission.
Conditions and Correctinn
Condition: Transmission slips in all selector lever positions
Correction:
1. Check modulating pressure, adjusting if necessary. If not
adjustable, check movement of modulating pressure control
valve. Clean modulating pressure safety valve in shift
valve housing uppcr section.
2. Check whether vacuum line
from
intake branch to vacuum
box is plugged. If yes, replace.
3. Check operating pressure. If too low or not available:
a) Disassemble and clan shift valve housing. and service
operating pressure contrul valve.
b) Remove and inspect primary pump, replacing if necessary
Condition: Transmission grabs 01 car vibrates when moving off
Correction: 1. Check modulating pressure, adjusting if necessary.
2. Pull off vacuum line from vacuum box, checking whether
ATF or fuel escapes.
a) lf ATF, replace vacuum box
b) If fuel, check fuel injection system and repair,
Primed in Germany - I, 1978
Troubleshooting
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