A/T - AOD 4th Gear Complaints

TRANSMISSION: AOD

BULLETIN: # 045

SUBJECT: 4th Gear Complaints

APPLICATION: Ford RWD

DATE: March 1991


No 4th, Late 4th, Falls Out Of 4th

Step 1.
Check the line pressure at 1200 RPM.

Step 2.
Reset the throttle valve (TV) pressure.

Step 3.
Check for low governor pressure. To do this, perform two checks while on the road test: Check for a wide open throttle 1-2 upshift. Check for a wide open throttle 3-2 downshift from a cruising speed of 35 mph. If there is no W.O.T. 1-2 upshift and there is a 3-1 downshift in place of a 3-2 downshift, suspect low governor pressure see "Checking Governor For Leaks".

Step 4.




Install a gauge on the forward pressure port and one on the direct pressure port. The pressure port locations are on the passenger side of the vehicle.

Accelerate to 55 mph in the "3" position and check the gauge readings. if the forward pressure is 10 psi or more higher than the direct pressure, there is a leak preventing the 3-4 shift. See "Checking Direct Clutch Leaks".

CHECKING FOR GOVERNOR LEAKS




If governor pressure is low, check the governor for loose bolts, dirty governor filter, stuck or dragging governor valve, worn governor valve bore, poor mounting surface and broken or incorrect spring (too light). Low governor pressure can be caused by things other than a bad governor. To find possible causes, slowly apply air through the governor to valve body port on the main shaft. With the pan off, look and listen for leaks in the governor circuit. Also check that the 3-4 shift valve moves freely.

Remove the pan. Apply 50 psi air pressure to the direct pressure port on the outside of the case.


CHECKING DIRECT CLUTCH LEAKS




Air will come out the exhaust port at the 2-3 shift valve. Seal the exhaust port with your thumb and air check again. Some locations to inspect for leaks are: Valve body gaskets, aluminum orifice control plug, 2-3 accumulator ring, ring bore in the rear of the case, cup plug in the output shaft, direct clutch cylinder ring sealing area, direct clutch seals and check ball in the direct piston.

^ To correct a leak at the aluminum orifice control plug; flare the plug using a tubing cutter and replace keeper with flat plate style E5AZ-7E335.

^ To correct a leak at the 2-3 accumulator ring: Use a metal or solid Teflon ring from a THM 200 1-2 accumulator piston.

^ To correct leaks at the valve body to case surface; flat file the case and use two valve body gaskets between the case and separator plate.

^ Do not torque valve body to more than 60 in. lbs..

FOR ADDITIONAL INFORMATION: 1990 Seminar Manual

BULLETIN RECAP

^ The governor can be checked during the road test.

^ A leak in the direct clutch can cause no 4th.

^ "Checking Governor For Leaks" will pinpoint governor leaks.

^ "Checking Direct Clutch Leaks" will pinpoint direct clutch leaks.