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7A2-2
1977 PONTIAC SERVICE MANUAL
Fig. 7A2-1 Turbo Hydra-Matic 2 5 0 Transmission
-
Sectional View
DIAGNOSIS
SEQUENCE FOR DIAGNOSIS
1. Check and correct fluid level.
2. Check detent downshift cable adjustment.
3. Check and correct vacuum line and fittings.
4. Check and correct manual linkage.
5. Road test vehicle:
a. Install oil pressure gage.
b. Road test using all selective ranges, noting when
discrepancies in operation or oil pressure occur.
c. Attempt to isolate the unit or circuit involved in the
malfunction.
d. If engine performances indicates an engine tune-up is
required, this should be performed before testing is completed
or
transmission
correction
attempted.
Poor
engine
performance can result in rough shifting or other
malfunctions.
FLUID CHECKING PROCEDURES
Refer to "Maintenance and Adjustments" section for
fluid checking procedures.
FLUID LEAK DIAGNOSIS
Determining Source of Fluid Leak
Before attempting to correct a fluid leak, the acutal
source of leak must be determined. In many cases, source of
leak can be deceiving due to "wind flow" around engine and
transmission.
The suspected area should be wiped clean of all fluid
before inspecting for source of leak.
The use of a "Black Light" to locate point at which fluid
is leaking is helpful. Comparing fluid from leak to that on
engine or transmission dipstick, when viewed by black light,
will determine source of leak
-
engine or transmission.
Fluid leaks around engine and transmission are generally
carried toward rear of vehicle by air stream. For example, a
transmission oil filler tube to case leak will sometimes appear
as a leak at rear of transmission. In determining source of a
leak, proceed as follows:
1. Degrease underside of transmission.
2. Road test to get unit at operating temperature.
3. Inspect for leak with engine running.
4. With engine off, check for fluid leaks due to raised
fluid level caused by drain back.
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