A/T - No 3rd to 4th Gear Upshift or Slipping 4th Gear
83ford12Article No. 83-13-10
TRANSMISSION - AUTOMATIC - AOD
- NO 3-4 UPSHIFT OR SLIPPING 4TH GEAR
FORD
1980-83 FORD, THUNDERBIRD, LTD
LINCOLN-MERCURY 1980-83 MERCURY, COUGAR, LINCOLN, MARK, CONTINENTAL, MARQUIS
LIGHT TRUCKS 1981-83 F-SERIES AND E-SERIES
Customer concerns of a no 3-4 upshift or a slipping 4th gear can result from causes such as: the direct clutch check ball leaking, miscellaneous leakage or a blocked hydraulic circuit condition, improper torque on the valve body or sticking valves, a leaking governor, the converter damper/hub assembly malfunctioning.
Replacement of the direct clutch cylinder piston assembly to alleviate check ball leakage has been effective in most instances.
To verify the direct clutch circuit leakage concern, perform the pressure test below as stated previously. Leakage in the direct clutch circuit has been attributed
most of the time to a leaking check ball in the direct clutch piston. Replacement of the direct clutch piston will alleviate this condition. However, since other factors can be involved, the following additional checks/verifications are listed to aid you in a complete comprehensive concern diagnosis for customer symptoms of a no 3-4 shift or a slipping 4th gear.
NOTE: To alleviate the direct clutch check ball wedging concern in the piston, a star washer replaced the staking operation mid-March, 1983. All current service parts depot stock have the updated direct clutch piston level.
Preliminary Checks/Information Verify the following steps have been accomplished:
^ Road test the vehicle to verify the customer complaint. A no 3-4 upshift is characterized by staying in 3rd gear. A slipping 4th gear is characterized by engine cut-loose on the 3-4 upshift and no 4th gear drive capability.
^ Check TV rod and see if bent or sticking.
^ Check TV linkage (could be misadjusted long).
Bent, sticking or misadjusted TV linkage will not properly synchronize with the carburetor lever at the time a 3-4 shift should occur.
^ Check control pressure and throttle pressure to identify that they are within specifications.
The new 3-4 shift valve (refer to TSB 83-10-11) changes the 3-4 shift pattern. The shift will occur at a higher mph.
Direct Clutch Pressure Test
The direct clutch pressure test outlined below will diagnose a low pressure condition or leakage in the direct clutch circuit. A difference of 15 psi or more between direct clutch pressure and line pressure (read at the forward clutch pressure tap) will prevent a 3-4 shift.
1. Attach 0-300 psi pressure gages to the forward clutch pressure tap and to the direct clutch pressure tap. Gage accuracy must be capable of distinguishing a 15 psi difference. (If this test is done in conjunction with a control pressure test, pressure gages will be attached to all pressure taps.) Have sufficient flexible hose to read the gages in the vehicle.
CAUTION: PRESSURE GAGES AFFECT THE SHIFT QUALITY OF THE TRANSMISSION. CARE SHOULD BE TAKEN NOT TO ACCELERATE OR DECELERATE RAPIDLY. POSSIBLE TRANSMISSION FAILURE COULD RESULT.
2. Drive the vehicle. When pressure is applied to the direct clutch, note the difference between the line pressure read at forward clutch pressure tap and the direct clutch pressure.
3. If the difference in pressures is less than 15 psi, the direct clutch circuit is OK.
4. If the difference is greater than 15 psi, there could be a leak in the direct clutch pressure circuit. (Proceed to the No 3-4 Upshift With Direct Clutch Pressure Greater Than 15 PSI Diagnostic Procedure). If the difference does exceed 15 psi, the gages on line pressure and direct clutch pressure can be switched to confirm that gage calibration difference is not the cause. (Proceed to the No 3-4 Upshift With Direct Clutch Pressure Less Than 15 PSI Diagnostic Procedure or to the Slipping 4th Gear Diagnostic Procedure if applicable).
No 3-4 Upshift With Direct Clutch Pressure Greater Than 15 PSI (Indicates Linkage) Diagnostic Procedure
NOTE: Direct clutch plates burnt will help to confirm leakage in the direct clutch circuit. Replacing only the plates and not finding the cause could result in a repeat service.
^ Check torque on valve body bolts.
^ Check to see if main control gasket is blocking an orifice.
^ Check for nicks or porosity in the case passages (valve body to case mating surface).
^ Check the direct clutch piston check ball for leakage
- inspect the piston check ball for freedom of movement. Improper seating of check ball will cause leakage. Leakage can be detected by turning the piston upside down (flat side of piston facing you) allowing the check ball to seat in the piston. Pour a small quantity of solvent over the check ball. If solvent drops past the check ball, replace the piston.
^ Inspect the output shaft feed passages and the cup plug for leakage. Apply 5-10 psi air to the output shaft feed passages. Refer to the AOD operation and diagnosis guide (course 1720-001) p. 32 for location of the feed passages. If air comes out the wrong feed passage, replace the output shaft.
^ Check direct clutch piston seal rings (inner and outer) for leakage.
^ Check all direct clutch output shaft seals for freedom of movement and for metal shavings and burrs between seal and output shaft.
^ Check the direct clutch cylinder for groove marks on the rear ID of the drum. Groove marks indicate the small cast iron seal rings are turning with the output shaft and grooving the cylinder. Groove marks may be caused by contamination or burrs in the output
shaft ring groove causing the seal rings to turn with the output shaft. Visually check the output ring grooves carefully. Replace as necessary the output shaft, the seal rings and the cylinder.
No 3-4 Upshift With Direct Clutch Pressure Less Than 15 PSI (Indicates No Leakage In The Direct Clutch Circuit) Diagnostic Procedure
^ Clean the valve body. Check for sticking valves as follows: Overdrive servo regulator valve; 3-4 shift valve; 3-4 TV modulator valve; orifice control valve. If any valves are sticking and they cannot be freed, replace valve body.
^ Reduce valve body bolt torque to minimum side of specification 80 in.lbs.
^ Check the fit of the governor counterweight on the output shaft. If the fit is sloppy, replace the counterweight.
^ Check the governor to output shaft retaining ring to make sure it is properly seated on the output shaft. Service as necessary.
^ Check last two large seal rings on the output shaft (#9, #10). They should move freely. Check for metal shaving contamination or burrs between the seal and output shaft. Replace as necessary.
^ Check the seal ring bore at the rear of case for scoring. Light scoring is permissable. Deep grooving indicates case wear. Replace case for deep grooving.
Slipping 4th Gear Diagnostic Procedure
NOTE: Burnt overdrive band will help confirm leakage in the overdrive circuit. Replacing only the overdrive band without finding the cause will result in a repeat service. If the overdrive band is not burnt, the converter damper/hub weld has usually been found to be suspect.
^ Check overdrive servo cover O-rings and servo piston seal for possible leakage. Replace O-rings and seal if leakage is evident.
^ Verify the overdrive servo cover is not cracked/porous. Coat cover with fluid. Apply air to overdrive servo, apply passage using tool (T80L- 77030-B). Observe to see if air bubbles are present on overdrive servo cover. Replace cover if air bubbles are present.
^ Check the overdrive servo case apply passage to see if it is blocked. Air pressure test. Replace case if necessary.
^ Verify the overdrive servo piston is seated correctly to the band end seat.
^ Verify the overdrive band is seated correctly to anchor pin.
^ Check the torque converter for damper/hub weld
failure. Perform converter damper/hub assembly weld check procedure. Refer to Shop Manual, Section 17-01. Use special service tools T83L-7902-
A. Replace converter if shaft turns more than two degrees or if there is a grinding noise while applying 50 ft.lbs. torque.
^ Check splines on both ends of the direct driveshaft and in direct clutch cylinder for distortion.
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