Road Testing
ROAD TESTBefore road testing, be sure the fluid level, throttle and gearshift linkage adjustments have been checked and corrected if necessary.
Observe engine performance during the test. An engine malfunction will have an adverse effect on transmission operation. In addition, operate the transmission in all gearshift positions to check for slippage and shift variations. Note whether the shifts are harsh or spongy, and check the speeds at which upshifts and downshifts occur.
Watch closely for slippage or engine speed flare-up which usually indicates clutch, band or overrunning clutch problems. If the condition is advanced, an overhaul may be necessary to restore normal operation.
In most cases, a slipping clutch or band can be determined by noting transmission operation in all gearshift lever positions and by comparing which internal units are applied in those positions. The Clutch and Band Application Chart provides a basis for analyzing road test results.
Analyzing the Road Test
Clutch And Band Application Chart:
Refer to the Clutch and Band Application Chart and note which elements are in use in the various gear ranges. The rear clutch is applied in all forward ranges (D, 2, 1). The overrunning clutch is applied in first gear D and 2 range only and the front band is applied in 1 and R range only.
For example, if slippage occurs in D and 2 range first gear but not in 1 range, the overrunning clutch is slipping. Similarly, if slippage occurs in any two forward gears, the rear clutch is slipping.
Applying the same method of analysis, note that both clutches are applied in D third gear only. If the transmission slips in third gear, either the front clutch or the rear clutch is slipping. By selecting another gear which does not use one of these units, the slipping clutch can be determined. For example, if the transmission also slips in reverse, the front clutch is slipping. If the transmission does not slip in reverse, the rear clutch is slipping.
This process of elimination can be used to determine the slipping unit and to check operation. The key is proper use of the Clutch and Band Application Chart.
Although road test analysis will help determine the slipping unit, the actual cause of a malfunction usually cannot be ascertained until hydraulic and air pressure tests are performed. Practically any condition can be caused by leaking hydraulic circuits or sticking valves.
Unless the condition is obvious, such as no drive in D range first gear only, do not disassemble the transmission until hydraulic and air pressure tests have been performed.