Transmission rear seal instalation

You have to pull the TRANSAXLE or TRANSMISSION to change the SEAL.

This is also a good time to change the Clutch if it is a Manual

For the rear seal, remove the drive shaft, and the seal should be very visible there. Very fortunate, as this is the easiest and cheapest seal there is to replace! Be extremely careful installing the new one, if using a hammer or similar installation item. If it isn't seated properly the leak will continue. Good luck.

You must remove the transmission to replace the rear main, you must have the special tools to install it as well or you will just have another leak within a very short time after installing the new rear main seal.

Remove the transmission and then the flex plate. Use an awl to pry out the seal and clean the area. Install the new seal around the crankshaft and with a seal installer push the new seal to its seat.

I'm not sure if this is the right part of your car but, are you talking about the rear seal on the engine for the crankshaft?

If so:

Rear Main Oil Seal REMOVAL & INSTALLATION 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.

1. Remove the starter.
2. Remove the transmission from the vehicle, following the procedures in Section 7.
3. On a manual shift transmission, remove the pressure plate and cover assembly and the clutch disc following the procedure in Section 7.
4. Remove the flywheel attaching bolts and remove the flywheel and engine rear cover plate.
5. 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. To install:
   
6. Clean the oil seal recess in the cylinder block and main bearing cap.
7. 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.
8. 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.
9. On a manual shift transmission, install the clutch disc and the pressure plate assembly following the procedure in Section 7.
10. Install the transmission, following the procedure in Section 7.

If it's oil, it's coming from the rear main seal.. I would go with this idea.

The seal doesn't cost much but the labor to get to it does.

To give you an idea what is involved the procedure is illustrated below from the service manual:

Removal & Installation 3.8L Engine To Remove:

1. Drain the engine coolant.
2. Drain the engine oil.
3. Remove the oil pan.
4. Remove the engine flywheel.
5. Remove the rear oil seal housing and gasket. Rear seal removal 3.8L
   
   
6. Remove the rear main seal by placing the housing face down on 2 blocks of wood. Using a drift tool and hammer tap the seal out of the housing.

To Install:
NOTE: Do not lubricate the rear main oil seal or the installation tool. Do not touch the sealing lip of the rear main seal once the protective sleeve is removed.
NOTE: Use a clean lint free cloth to clean the crankshaft sealing surface. Remove sharp edges or burrs that could damage the rear main oil seal. Remove burrs or sharp edges with a crocus cloth.

1. Carefully remove the rear oil seal from the protective sleeve.
2. Install the oil seal onto the seal driver EN-47623 or equivalent by placing the seal at an angle and twisting until it is fully seated.
3. Install the seal into the housing using the seal driver EN-47623 or equivalent and driver handle J-8092 or equivalent. Apply downward force until the seal is seated. NOTE: Ensure that the housing gasket is installed correctly and that the oil passages are not blocked.
   
4. Using a new gasket Install the rear oil seal housing on the engine being careful not damage the rear main seal. NOTE: The plastic inserts are used in production and are not needed for assembly.
   
5. Hand tighten the bolts. Rear seal housing alignment 3.8L
   
   
6. Place a straight edge on the crankshaft rear oil seal housing flange and the engine block oil pan flange. Using a feeler gauge check that there is no more than .0004 in (0.10 mm) step on each side. Rotate the housing to make the steps equal on both sides.
7. Tighten the housing bolts 11 ft-lb (15 Nm) plus an additional 50 degrees.
8. Ensure that the housing did not move out of specification. Repeat step 6 if the oil seal housing is not within the specified range. Replace the rear oil seal housing if the specified measurement can not be reached.
9. Install the flywheel.
10. Install the oil pan.
11. Fill the engine oil and the cooling system.
12. Check for leaks

5.3L Engine To Remove:

1. Remove the flywheel from the crankshaft.
2. Remove and discard the crankshaft rear oil seal from the rear cover.

To Install:

1. Use clean engine oil to lubricate the outside diameter of the crankshaft rear oil seal and rear cover oil seal bore.
2. Install the tapered cone and bolts of a J 41479 or equivalent crankshaft rear oil seal installer onto the crankshaft.
3. Place the crankshaft rear oil seal onto the tapered cone.
4. Install the threaded rod of the J 41479 crankshaft rear oil seal installer into the tapered cone. Rear main seal installer 5.3L
   
   
5. Install the crankshaft rear oil seal by turning the handle of the J 41479 clockwise.
6. Remove the J 41479 crankshaft rear oil seal installer from the crankshaft.
7. Install the flywheel onto the crankshaft.

--- I'm not sure what the exact cost would be as the hours were not listed for this procedure on my online resource.

This is most likely a leak from your rear main seal. It happens and can be a pain to replace if you're a DYI kinda person without the nec. equipment.

1. Raise and safely support the vehicle with jackstands.
   
2. Remove the transmission.
   
3. If equipped with a manual transmission, remove the clutch and pressure plate.
   
4. Remove the flywheel assembly.
   
5. Using a suitable prytool, carefully pry the old seal out.
   

6. Inspect the crankshaft for nicks or burrs, correct as required.
Crankshaft rear main seal - 5.7L engine

To install:

1. Clean the area and coat the seal with engine oil. Install the seal onto tool J-34686 for 3.4L engines, J 41349 for 3.8L engines or J 35621 for 5.7L engines.
   
2. Install the tool (with the seal mounted to it) onto the rear of the crankshaft. Tighten the screws snugly to be sure the seal will be installed squarely over the crankshaft.
   

Exploded view of the rear main seal installation - 3.4L engine
Click to Enlarge

1. Tighten the wing nut on the installation tool until it bottoms out.
   
2. Remove the tool from the crankshaft or rear oil seal housing, as applicable.
   

Rear main seal and installation tool - 3.8L engine
Click to Enlarge After position the seal on the tool, install it to the crankshaft housing

1. Install the flywheel.
   
2. If equipped with a manual transmission, install the clutch and pressure plate.
   
3. Install the transmission.
   
4. Check the fluid levels, start the engine and check for leaks.
   

A leaking rear main seal will not cause your transmission to leak.

The transmission has its own seal and should not leak because of the engine rear main seal.

Due to the labor involved in replacing the rear main seal on the engine, it is best if you replace the front transmission seal at the same time if possible.

Installation varies on different vehicles but the principles are the same.

it sounds like you have a tail shaft seal gone in the transmission it's not a difficult fix if you are handy. Remove the drive shaft and remove the tail stock seal(there are install and removal tools but a hammer and a screwdriver will remove it nicely)then replace with new seal (if you don't have the install tool a 5" long piece of 2x4 and a hammer works BE GENTLE!!!!)and reinstall drive shaft..........these seals are available at your local auto parts store and are usually no more tan $10.00
hope this helps!.........good luck!