TM-9-2320-280-34

TRUCK, UTILITY: M998 SERIES

TECHNICAL MANUAL; DIRECT SUPPORT AND GENERAL SUPPORT MAINTENANCE

JANUARY 1996
TM-9-2320-280-34

  TM-9-2320-280-34 - Page 40 of 1258

TM 9-2320-280-34
Table 2-1. Mechanical Troubleshooting (Cont ’d)
MALFUNCTION
TEST OR INSPECTION
30.
NO 1-2 UPSHIFT OR DELAYED UPSHIFT
Step 1.
If oil pressure in “
D "(overdrive) at 1000 rpm is normal, proceed to step 2. If oil pressure is high, proceed
/
to step 3.
Step 2.
Check results of control valve and governor line pressure test (TM 9-2320-280-20).
Step 3.
If oil pressure in N" (neutral) at 1000 rpm was normal, proceed to st
ep 4. If oil pressure was high, proceed
to step 4.
Step 4.
Check control valve spacer plate for obstructions. Clean or replace spacer plate (chapter 17).
END OF TESTING!
31.
1-2 SHIFTS SOFT OR SLIPS
Step 1.
Check transmission oil pressure response to varying throttle openings. Pressure should respond rapidly to
quick changes in throttle opening. If oil pressure response is poor, proceed to step 2. If oil pressure response
is normal, proceed to step 3.
Step 2.
If oil pressure in “
D “
(overdrive) at 1000 rpm is low, proceed to step 3. If oil pressure is normal, proceed
to step 9.
Step 3.
Check oil pump for obstructed oil passages or damage. Repair oil pump (para. 17-29).
Step 4.
Check forward clutch seals for damage. Replace damaged seals (para. 17-22).
Step 5.
Check center support oil seal rings for damage. Replace damaged rings (para. 17-20).
Step 6.
Check rear servo piston and oil seal rings for damage. Repair rear servo (para. 17-27) if damaged.
Step 7.
Check front accumulator piston and oil
seal rings for damage. Replace control valve (chapter 17) if
accumulator piston components are damaged.
Step 8.
Check transmission case for internal damage or porosity. Replace transmission (para. 7-8) if case is damaged
or porous.
Step 9.
Inspect control valve for nicks on machined surfaces or voids in casting, check 1-2 accumulator valve train
for stuck valves or incorrect assembly; check front accumulator piston and oil seal rings for damage. Replace
control valve (chapter 17) if any damage is fo
und.
Step 10
Check rear servo and rear accumulator pistons and oil seal rings for damage. Repair rear servo
(para. 17-11) if damaged.
Step 11.
Check center support bolt for looseness. Tighten to 20-25 lb-ft (27-34 N-m).
WARNING
Compressed air used for cleaning purpose will not exceed 30 psi (207
kPa). Use only with effective chip guarding and personnel protective
equipment (goggles, shield, gloves, etc.).
Step 12.
Air check intermediate clutch piston for proper operation. If operation is normal, p
roceed to step 13. If piston
exhibits excessive leakage, proceed to step 14.
Step 13.
Check intermediate clutch piston, plates, and release springs for damage or incorrect assembly. Repair
intermediate clutch piston (para. 17-25) if damaged.
Step 14.
Check center support for missing orifice plug. Replace transmission (para. 7-8) if plug is missing.
END OF TESTING!
2-14


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