A/T - Intermittent Delayed Upshifts
90oldsmobile04SUBJECT INTERMITTENT DELAYED UPSHIFTS WHEN COLD OR
HOT - TV PLUNGER/BUSHING ASSEMBLY NOW AVAILABLE - 1984-90 MODELS WITH 4T60
MODELS/YEARS 1984-1990 CUTLASS CIERA - 1988-1990 CUTLASS
SUPREME - 1986-1990 EIGHTY-EIGHT - 1985-1990 NINETY-EIGHT - 1986-1990 TORONADO EQUIPPED WITH HYDRA-MATIC 4T60 (THM 440-T4) (RPO-ME9)
NUMBER: 90-T-56
CORP.REF.NO: 077106
DATE: March 1990
SECTION: 4T60
BULLETIN COVERS:
Background and diagnosis information on the throttle valve (T.V.) and governor system that control shift timing and not shift feel. The T.V. plunger/bushing assemblies will now be available for service. Before the T.V. plunger/bushing assembly is replaced, the entire T.V. system must be checked. The T.V. SYSTEM may cause one or more of the following conditions:
- Delayed upshifts (may also be caused by sediment between the governor seat and ball(s).
- Early upshifts (may also be caused by the governor weight(s) binding on the governor rotor). The rotor is not indexed correctly.
- No upshifts (may also be caused by sediment between the governor seat and balls).
- 1-2 shift at full throttle only.
- No full throttle or part throttle detent downshifts.
- Intermittent second gear starts.
- Harsh 3-2 downshifts.
Figure 1 - T.V. Plunger/Bushing And Throttle Valve:
IMPORTANT: Some of the conditions listed above could be intermittent or all the time. The T.V. plunger and bushing (308 and 309) may be worn, allowing sediment to cause the plunger to stick in the bore intermittently. Another concern could be the throttle valve (311) being stuck down in the bore. Sediment could be the cause of both of these concerns. Either of these conditions could cause delayed upshifts when the transaxle is cold or hot. (Figure 1)
The listed conditions may be caused by a T.V. cable that is:
- Improperly set
- Kinked or binding
- Disconnected
- Broken
- Wrong part
DIAGNOSIS:
^ Check T.V. cable for correct part number, listed in the parts catalog.
^ Check T.V. cable for kinked, binding, disconnected or broken condition.
^ Check T.V. cable for proper setting.
^ Is there tension on the T.V. cable when being pulled and being released (with engine off)?
- If the T.V. system fails this test, it could be caused by a disconnected throttle lever to cable link (49), a stuck T.V. plunger in the T.V. bushing or a broken T.V. cable.
If the T.V. cable has tension when the engine is off but when the engine is started, the cable goes slack. The T.V. plunger is being sucked Into the bushing because the T.V. plunger assist that reduces accelerator pedal effort is receiving too much pressure.
The throttle valve (311) may be sticking or stuck in the bore. This could be caused by sediment. The valve must move freely In the bore. Clean the valve and bore so the valve moves freely in the bore. Follow the procedures outlined in Dealer Technical Bulletin 86-T-23 (Corporate Reference Number 8067907).
NOTICE: Excessive lapping of the valves for a HYDRA-MATIC 4T60 (THM 440-T4) may cause the valves to stick. Too much lapping can take the sharp cleaning edge off the valve land. Sediment can now wedge between the valve land and bore, causing the valve to stick. Also, the lapping material can impregnate into the valve lands, causing the valve bore to excessively wear. This will cause the valves to stick unless the valves are lightly lapped.
If the throttle valve moves freely in the bore, then the pump cover is missing the machining of the throttle valve (311) exhaust.
Check the governor system for rise in pressure of approximately 1 PSI (6.895 kPa) for every MPH (1.6093 km/h) when a pressure gauge is connected to the governor pressure tap.
IMPORTANT: Some "rules of thumb" for governor pressure:
- At 0 MPH (O km/h) the PSI will be about 0 - 4 (0 - 27.58 kPa) depending on the model.
- Below 30 MPH (48 km/h) the pressure in PSI (only) will be at or below the MPH reading by as much as 6 PSI (41.37 kPa); above 30 MPH (48 km/h) the pressure in PSI (kPa) will be at or somewhere above the MPH reading by as much as 20 PSI (137.9 kPa).
- The reading for a cold transaxle and hot transaxle should be about the same; if not, then orifice # 5 - a slot in the accumulator cover gasket (119) - may be clogged or the governor assembly could be leaking. Orifice # 5 temperature compensates the flow needs in the governor circuit. Also, the accumulator cover to case bolt(s) could be loose, causing the cold governor pressure reading to be much higher than the hot reading pressure. This would allow 4th gear when cold and no 4th gear when hot.
- A clogged governor screen that is in the case will cause early upshifts and not delayed upshifts.
*The bottom line is that governor pressure MUST increase with MPH (km/h).
SERVICE PROCEDURE:
If during the diagnosis of the T.V. and governor system it is found that the T.V. plunger/bushing assembly is worn/sticking/binding, replace the assembly with the parts listed in SERVICE PARTS INFORMATION.
SERVICE MANUAL REFERENCE:
See the 1984-90 Service Manual for repair procedures.
SERVICE PARTS INFORMATION: