Wont shift into 3rd 4th or overdrive

Have a look at your EGR valve first, 326 is an egr code.
A tech bulletin on the tranny shift problem is as follows.
AX4N TRANSAXLE - NO 4TH GEAR / NO 3-4 SHIFT / DTC TECHNICAL SERVICE BULLETIN Reference Number(s): 98-10-7, Â Date of Issue: Â May 26, 1998 Related Ref Number(s): 98-10-7 ARTICLE BEGINNING CONDITIONS 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 FOR FORWARD CLUTCH CONTROL VALVE - SERVICE TIP APPLICATION Model(s): Ford: 1994-98 Taurus Lincoln-Mercury: 1994-98 Sable 1995-98 Continental Bulletin No.: 98-10-7 Date: May 26, 1998 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 ( Fig. 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 ( Fig. 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 ( Fig. 2 ). 4. Any time service is required on any AX4N transaxle main control, inspect the retaining clip for the forward clutch control valve to be sure it is the latest design level, and replace the retaining clip if it is not. The revised clip is larger and will remain centered in the valve body casting groove. PARTS INFORMATION PARTS INFORMATION WARRANTY INFORMATION WARRANTY STATUS: Eligible Under The Provisions Of Bumper To Bumper Warranty Coverage. OPERATION: 981007A DESCRIPTION: Inspect/Repair/Replace Main Control Valve Body TIME: 2.4 Hrs. DEALER CODING: BASIC PART NO.: 7F194 CONDITION CODE: 01 OASIS CODES: 501000, 502000, 503000, 503300, 503400, 504000 Fig. 1: Forward Clutch Controller Valve Fig. 2: Retaining Clip For Forward Clutch Controller Valve Part Number Part Name F8DZ-7F194-AA Forward Clutch Control Valve Retaining Clip

One would think so, but I have seen stranger things!

If you have a hand vacuum pump, remove the vac lint to the egr, attach the pump, pump it up, if the car stalls, EGR is working. Make sure there is no carbon blocking the pintle from bottoming in it's bore.