Here is another possibility:
A/T - 4R44E/5R55E Whistling/Hissing Noise At Idle
Article No.
98-5-14
03/16/98
^ NOISE - "WHISTLING/HISSING" FROM
TRANSMISSION MAIN CONTROL AREA DURING
IDLE - VEHICLES WITH 4R44E OR 5R55E
TRANSMISSION
^ TRANSMISSION - 4R44E OR 5R55E -
"WHISTLING/HISSING" NOISE FROM MAIN
CONTROL AREA DURING IDLE
LIGHT TRUCK:
1997 AEROSTAR
1997-98 EXPLORER, MOUNTAINEER, RANGER
This TSB article is being republished in its entirety to include one chart to clarify the parts needed for repair.
ISSUE:
A "whistling" or "hissing" noise from the main control area may occur while idling in Drive and/or Reverse on some vehicles that have either a 4R44E or 5R55E transmission. This may be due to an improperly sized orifice hole in the main control separator plate.
ACTION:
Replace the separator plate with a revised separator plate. Refer to the following Service Procedure for details.
SERVICE PROCEDURE
1. Perform normal diagnosis by referring to the appropriate model/year Service or Workshop Manual.
2. Repair all Diagnostic Trouble Codes (DTCs) as listed.
3. Repair all transmission concerns as required.
4. Verify that the whistle/hiss noise still exists. If the condition still exists, install the revised Separator Plate (-7A00

onto the main control. Refer to the Service Manual for proper procedure. Refer to the Application Chart for the correct separator plate.
NOTE : IF A SYMPTOM OTHER THAN "WHISTLING/HISSING" REQUIRES REPLACING THE MAIN CONTROL, REFER TO THE MAIN CONTROL CHART WITH THE UPDATED PART NUMBERS FOR CORRECT APPLICATION.