Jeep Cherokee (XJ): Automatic transmission diagnosis. Effects of incorrect fluid level. Causes of burnt fluid

Jeep Cherokee (XJ) 1984 - 2001 Service Manual > Transmission and transfer case > Automatic transmission-30RH > Diagnosis and testing > Automatic transmission diagnosis. Effects of incorrect fluid level. Causes of burnt fluid

Automatic transmission diagnosis

Automatic transmission problems can be a result of poor engine performance, incorrect fluid level, incorrect linkage or cable adjustment, band or hydraulic control pressure adjustments, hydraulic system malfunctions or electrical/mechanical component malfunctions.

Begin diagnosis by checking the easily accessible items such as: fluid level and condition, linkage adjustments and electrical connections. A road test will determine if further diagnosis is necessary.

Fig. 53 Governor-High Output Shaft Rotation
Fig. 53 Governor-High Output Shaft Rotation

Effects of incorrect fluid level

A low fluid level allows the pump to take in air along with the fluid. Air in the fluid will cause fluid pressures to be low and develop slower than normal.

If the transmission is overfilled, the gears churn the fluid into foam. This aerates the fluid and causing the same conditions occurring with a low level. In either case, air bubbles cause fluid overheating, oxidation and varnish buildup which interferes with valve, clutch and servo operation. Foaming also causes fluid expansion which can result in fluid overflow from the transmission vent or fill tube. Fluid overflow can easily be mistaken for a leak if inspection is not careful.

Causes of burnt fluid

Burnt, discolored fluid is a result of overheating which has two primary causes.

(1) A result of restricted fluid flow through the main and/or auxiliary cooler. This condition is usually the result of a faulty or improperly installed drainback valve, a damaged main cooler, or severe restrictions in the coolers and lines caused by debris or kinked lines.

(2) Heavy duty operation with a vehicle not properly equipped for this type of operation. Trailer towing or similar high load operation will overheat the transmission fluid if the vehicle is improperly equipped. Such vehicles should have an auxiliary transmission fluid cooler, a heavy duty cooling system, and the engine/axle ratio combination needed to handle heavy loads

Fig. 54 Ignition Interlock Cable Routing
Fig. 54 Ignition Interlock Cable Routing

1 - SHIFT MECHANISM
2 - LOCK-TAB
3 - IGNITION LOCK INTERLOCK
4 - STEERING COLUMN
5 - SOLENOID
6 - WIRE CONNECTOR
7 - LEVER
8 - MOUNT BRACKET
9 - SHIFT CABLE
10 - AUTOMATIC TRANSMISSION
11 - TIE STRAP
12 - PARK/BRAKE INTERLOCK CABLE

Fig. 55 Ignition Key Cylinder Actuation
Fig. 55 Ignition Key Cylinder Actuation

1 - SLIDER LOCKED
2 - CAM RETURN SPRING
3 - INTERLOCK CABLE
4 - CAM
5 - SLIDER

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