You will have to pull the transmission to change the rear main seal. So that means you will have to take out the drive shaft, then transfer case and then the transmission. It sounds like a lot but it is not that hard on these. I will give you a little tip that will save you time and money, there is a park/neutral switch that is on the transmission. The connector that plugs in to this is glued in, so you will not be able to unplug it. You will need to remove the two 10mm bolts that hold it on the transmission and slide it off the shaft. I have seen many people try to unplug these and end up breaking them. Here is a pic of it.
When you remove the transfer case, take off the 15mm nuts that hold it to the adapter and leave the adapter on the transmission. If you need any more help, just ask.
Park/Neutral Position Switch Replacement
Once you get the flywheel off, you can use a seal puller or large screw driver to pry the old seal out. There is a tool that is used to press the rear main in, but you can do it without it if you are careful. The new seal should come with a plastic ring already in it that will help get it started over the crankshaft. After that you can use a light hammer and a half inch drive extension (or anything else that is flat on the end like a large socket) and just tap around the seal lightly and evenly until the gasket is in the same place as the old one was. The adapter is between the transmission and transfer case. It has 15mm bolts that hold it to the transmission and 15mm nuts that hold it to the transfer case. It is much easier to get the transfer case out if you unbolt it from the adapter and leave the adapter on the transmission than if you unbolt the adapter from the transmission and take it out with the transfer case. The park neutral switch is on the drives side and has a shaft that it slides on to. The shaft is what the shift cable rotates when you put it in gear. It has 2 plugs, one has 4 wires and the other has 6. Let me know if I can be of more help.
When I changed the oil pan gasket, it looked like there was a plate on the front (timing cover) and rear of the engine. While I am changing the main seal, should I go ahead and change the gasket at this rear plate? Could said gasket be the cause of my leak? My truck has 175K miles on it, but I take good care of it.
Thanks Butch. I am going to be tackling this project tomorrow. I might need you to come and help. My back's getting sore just thinking about it. Would it be any easier to pull the engine instead of dropping the tranny?
If it appears to be leaking I would go ahaed and chang it. This does however require the use of special alighnment tool. I will post the procedure and a pic of the tool. As far as pulling the engine instead of the transmission I would stick with the transmission. If you are doing this on a flat surface you can just remove the transfer case, unbolt the transmission and torque converter bolts, and use a floor jack with a piece of wood on it, and slide the transmission back far enough to get the flywheel off. The hardest part if you don't have a lift, is going to be getting the transfer case out, and getting the torque conveter bolts out.
Crankshaft Rear Oil Seal Housing Replacement
Installation Procedure - Cover with Seal
Notice: Refer to Fastener Notice in the Preface section.
Tighten Tighten the oil pan-to-rear housing bolts (4) to 12 N·m (106 lb in).
Tighten Tighten the bolts to 30 N·m (22 lb ft).
Installation Procedure - Cover without Seal
Important: The tapered legs of the alignment tool must enter the rear cover oil seal bore.