Bad OD would be shudder when attempting to transition to OD usually occuring at speeds above 40Mph. Usually at low throttle about 45mph or below 50% at speeds above 55mph.
It will feel like a misfire, but no misfires will be registered. You should get a code. P0741 or P0743 IIRC...
No 4th with no code could be a lot of things. Bad shift solenoid, broken wire, clogged valve train...
Here is a TSB if you haven't seen it already:
Article No.
98-10-7
05/26/98
^ TRANSAXLE - AX4N - NO 4TH GEAR AND DIAGNOSTIC TROUBLE CODES (DTCS) P0734
AND/OR P0761 FOR 1996-98 TAURUS/SABLE AND
1995-98 CONTINENTAL, AND DTC 648 FOR 1994-95
TAURUS/SABLE
^ TRANSAXLE - AX4N - RETAINING CLIP FORFORWARD CLUTCH CONTROL VALVE - SERVICE
TIP
FORD:
1994-98 TAURUS
LINCOLN-MERCURY:
1994-98 SABLE
1995-98 CONTINENTAL
ISSUE
No 4th gear operation (no 3-4 shift) and Diagnostic Trouble Codes (DTCs) P0734 and/or P0761 or 648 may occur on some vehicles. This may be caused by a broken retaining clip in the valve body that secures the forward clutch control valve and spring in place.
ACTION
Replace broken forward clutch control valve retaining clip with revised forward clutch control valve retaining clip. Refer to the following Service Procedure for details.
SERVICE PROCEDURE
1. Inspect for a broken retaining clip by removing the valve body and then the valve body separator plate. Inspect the forward clutch control valve, spring, retaining clip, and valve body casting for damage (Figure 1).
2. If the clip is broken and the forward clutch control valve and/or valve body casting is damaged, replace the main control. The retaining clip has just been revised to prevent the chance of breakage. The revised Retaining Clip (F8DZ-7F194-AA) has circular cutouts on the side of the clip in place of the square cutouts on the previous design level clip (Figure 2).
3. Inspect the new main control (if required) before installing it and replace this retaining clip for the forward clutch control valve and spring if it's not the new design (Figure 2) valve body
PART NUMBER PART NAME
F8DZ-7F194-AA Forward Clutch control valve
Retaining Clip
OTHER APPLICABLE ARTICLES: NONE
WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage
OPERATION DESCRIPTION TIME
981007A Inspect/Repair/Replace 2.4 Hrs