Rear Main seal replacment FAQ, Submitted by Roy Ireland. Spring, 2002

Hi Wagonvillers,

I finally got tired of cleaning oil from the underside of the wagon  after every road trip as a result of my leaking rear main seal. I've  had the new seal and pan gasket for almost a year but haven't gotten  the motivation to put it in. I had tried several other things to  avoid doing the rear seal including replacing the right bank head  gasket (which was also leaking) and retightening the pan bolts and  looking for leaks from other sources. I finally ran out of options. I've been checking posts on the Y-Block discussion list for tips and  tricks on how to replace the seal. Turns out it's pretty  straightforward. Just a PIA getting the pan off and working under the  car lying on your back. I removed the splash shields, torque convertor dust shield and the  pan bolts. In order for the pan to clear the cross member, the #5  piston must be at TDC. In that position, all the counterweights are  at their highest point. I used a compression gauge in the #5 cylinder  while cranking the engine with a remote starter switch to show me  when it was at TDC. Once the oil pump tube was disconnected from the 
pump, the pan slipped right out. I removed the journal block (sometimes called the seal block) and  inspected the old seal. I was hoping for some hard evidence at the  rear seal was leaking so I would feel my time and effort was worth  it. Sure enough, I had installed the seal backwards way back in 1993  when I rebuilt the engine. I have since learned that this is a  guaranteed way to make it leak! The packaging on the new neoprene  seal (NAPA part no. JV748) clearly shows a diagram of which way the  seal needs to be installed so I did it correctly this time. Removing the old seal was easy. I used an awl to tap one side of the 
seal in the block to get it started out of the channel. Then I was  able to grab the end with some needle nose pliers and pull it the  rest of the way out.
I carefully installed the new seal in the journal block and then in  the engine. It was a little tricky getting the seal started in the  groove between the crank and the block, but once I got it started, it  slipped right around the crank. The NAPA seal kit came with the kind of side seals that are supposed  to expand when they come in contact with oil. My old ones were  neoprene with a pin driven between the seal and the journal block to  provide a tight fit. 

Click here for a photo of each type of seal.  

I tried to  insert the new side seals but they caught on the edge of the groove  and peeled back some of the cardboard-like material that is supposed to expand. So I used my old neoprene seals instead. One of the Y- block mechanics on the discussion list said that would work fine. I put some Ultra Blue RTV sealer on the bottom of the journal block  and reinstalled it. Then I reinstalled the pan. This is a lot harder  than removing it. You have to get the pan gasket lined up on both  sides as you slide the pan back into position. I used Ultra Blue RTV  on the pan gasket too and had blue sticky stuff all over me by the  time I got it in. After six quarts of fresh oil and a new filter, I took it for a test 
drive around the block and didn't see any sign of a leak. Before, I  would see some drops forming on the bellhousing just from a short  trip like that.
The proof will be taking it out on the freeway for some high speed  driving. Hope it's fixed. I'm planning on attending several out of  town shows this spring and summer.

Later,
Roy