You need to remove the transmission.
REMOVAL & INSTALLATION
See Figures 1, 2 and 3
Fig. 1: Rear main seal installation for the 2.3L and 2.5L engines
Fig. 2: Removing the rear main seal
Fig. 3: Installing the rear main seal on the 2.9L engines
If the crankshaft rear oil seal replacement is the only operation being performed, it can be done in the vehicle as detailed in the following procedure. If the oil seal is being replaced in conjunction with a rear main bearing replacement, the engine must be removed from the vehicle and installed on a work stand.
Remove the starter.
Remove the transmission from the vehicle, following the procedures in Drive Train.
On a manual shift transmission, remove the pressure plate and cover assembly and the clutch disc following the procedure in Drive Train.
Remove the flywheel attaching bolts and remove the flywheel and engine rear cover plate.
Use an awl to punch two holes in the crankshaft rear oil seal. Punch the holes on opposite sides of the crankshaft and just above the bearing cap to cylinder block split line. Install a sheet metal screw in each hole. Use two large screwdrivers or small pry bars and pry against both screws at the same time to remove the crankshaft rear oil seal. It may be necessary to place small blocks of wood against the cylinder block to provide a fulcrum point for the pry bars. Use caution throughout this procedure to avoid scratching or otherwise damaging the crankshaft oil seal surface.
Clean the oil seal recess in the cylinder block and main bearing cap.
Clean, inspect and polish the rear oil seal rubbing surface on the crankshaft. Coat a new oil seal and the crankshaft with a light film of engine oil. Start the seal in the recess with the seal lip facing forward and install it with a seal driver. Keep the tool, T82L-6701-A (4-cyl. engines) or T72C-6165 (6-cyl. engine) straight with the centerline of the crankshaft and install the seal until the tool contacts the cylinder block surface. Remove the tool and inspect the seal to be sure it was not damaged during installation.
Install the engine rear cover plate. Position the flywheel on the crankshaft flange. Coat the threads of the flywheel attaching bolts with oil-resistant sealer and install the bolts. Tighten the bolts in sequence across from each other to the specifications listed in the torque chart in this section.
On a manual shift transmission, install the clutch disc and the pressure plate assembly following the procedure in Drive Train.
Install the transmission, following the procedure in Drive Train