Jeep Cherokee

 Service Manual

Transmission and transfer case » Automatic transmission-30RH » Diagnosis and testing
Analyzing road test

Refer to the Clutch and Band Application chart and note which elements are in use in the various gear ranges.

Verify that the rear clutch is applied in all forward ranges (D, 2, 1). The transmission overrunning clutch is applied in first gear (D, 2 and 1 ranges) only. The rear band is applied in 1 and R range only.

Verify that the overdrive clutch is applied only in fourth gear and the overdrive direct clutch and overrunning clutch are applied in all ranges except fourth gear. For example: If slippage occurs in first gear in D and 2 range but not in 1 range, the transmission overrunning clutch is faulty. Similarly, if slippage occurs in any two forward gears, the rear clutch is slipping.

Fig. 56 Clutch And Band Application

Applying the same method of analysis, verify that the front and rear clutches are applied simultaneously only in D range third gear. If the transmission slips in third gear, either the front clutch or the rear clutch is slipping.

If slippage occurs during the third gear and the direct clutch were to fail, the transmission would lose both reverse gear and overrun braking in 2 position (manual second gear). If the transmission slips in any other forward gears, the transmission rear clutch is probably slipping.

This process of elimination can be used to identify a slipping unit and check operation. Proper use of the Clutch and Band Application Chart is the key.

Although road test analysis will help determine the slipping unit, the actual cause of a malfunction usually cannot be determined until hydraulic and air pressure tests are performed. Practically any condition can be caused by leaking hydraulic circuits or sticking valves.

Unless a malfunction is obvious, such as no drive in D range first gear, do not disassemble the transmission.

Perform the hydraulic and air pressure tests to help determine the probable cause.

Automatic transmission diagnosis

Effects of incorrect fluid level

Causes of burnt fluid

Fluid contamination

Preliminary diagnosis

Park/neutral position switch

Gearshift cable

Throttle valve cable

Road testing

Analyzing road test

Hydraulic pressure test

Air testing transmission clutch and band operation

Converter housing fluid leak diagnosis

Diagnosis charts