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 36 of 1258

TM 9-2320-280-34
Table 2-1. Mechanical Troubleshooting (Cont'd)
MALFUNCTION
TEST OR INSPECTION
28.
TRANSMISSION NOISY
NOTE
Check engine accessory drive components: water pump, power steering pump,
alternator, and air conditioner compressor (if installed) for the source of
"noise" before checking transmission.
a.
Noise in Neutral and All Driving Ranges.
Step 1.
Check torque converter for loose mounting capscrews and damage. Tighten capscrews
or replace torque converter (para. 17-4) if damaged.
Step 2.
Check flywheel for damage. Replace flywheel (TM 9-2815-237-34) if damaged.
Step 3.
Check oil pump for obstructed oil passages, damage, and proper assembly. Repair oil
pump (para. 17-6) if damaged.
b.
Noise in First, Second, and Reverse.
Step 1.
Check gear unit thrust bearings and races for damage. Replace bearing(s) and races if
either is damaged (para. 17-10).
Step 2.
Inspect gears for damage and wear. Replace damaged or worn components (para. 17-
10).
Step 3.
Inspect front internal gear ring for damage. Replace gear ring if damaged (para. 17-10).
c.
Noise during Acceleration - Any Gear.
Check engine and transmission mounts for looseness or damage. Secure or replace
mounts (para. 3-3 or TM 9-2320-280-20).
END OF TESTING!
TRANSMISSION (4L80E)
NOTE
•
The 4L80-E Transmission is an electronically controlled four speed. The
Transmission Control Module (TCM), an on board computer, receives and
processes input signals from sensors on the vehicle and delivers output
signals to the solenoids located on the control valve assembly. These
solenoids control the transmission operating pressures, upshift and
downshift patterns and torque converter clutch (TCC) operation. Unit
Maintenance has recorded the Trouble Codes stored in the TCM. Refer to
TM 9-2320-280-20 for definitions of trouble codes.
•
In the event of a major transmission malfunction involving the torque
converter or oil pump, replace filter, flush oil cooler and lines before
replenishing fluid.
•
Perform the oil pressure tests (para. 1732) and record the readings for
use during troubleshooting.
•
Perform a road test (TM 9-2320-280-20).
•
Perform electrical check-out at transmission electrical connector of
malfunction 29.
2-12


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