Was wondering if anyone knows if the rear main engine seal (for a 72 w/auto tranny) is a two piece seal and if I have to remove the engine to get to it.  Or can I just remove the tranny to get to it????

Thanks,

Tina

It is a two piece seal. It is easier to change with the tranny out, but it can be done without removing it. It's best to go ahead & get the trans out of the way. You do not have to pull the engine to do this job.
You have to remove the steering linkage from under the pan, and then pull the pan. It's much easier if you don't have power steering, but not at all impossible.
Make sure the block & main cap is absolutely clean before installing the new seals.

Thanks for the info..... You guys rock!!!!!

I bought my Vette with 55k on the odometer, and felt I should look things over. I tend to run it up in the rpm catagory, so I dropped the pan and replaced all the main and rod bearings, and the rear seal. I also installed a Edelbrock gear drive for the camshaft, as I didn't want to go back with a chain. The rear seal was easy with just the pan off, and I have done it that way many times.

Pumps, since  you have done this one a few times, got any tips that can make the
 2 piece seal any better and keep us from having to do this wonderful job again?
Mine is leaking a small amount but it still bothers me. I would like to get the leak
fixed and not see it happen again.  

As stated, remove the oil pan first.  Take the cover off of the torque converter to allow more working room.  Even with the power steering if you drop the steering center link from the idler arm, you will have enough room to remove the pan.  You may need to rotate the crank to cause the crank balance weights to move to the upward position to have enough room.

Remove the single bolt holding on the oil pump and remove it.  Now remove the two rear main bearing cap bolts, and remove the cap.  Half of the two piece seal will drop out in the cap.  Just pop it out and put the new half in place.  Make sure the seal lip points in toward the engine, not out or you will be installing a leak.

It's easier to loosen all of the main bearing caps.  Just a couple of turns each.  This takes pressure off of the top half of the seal.  Now push the seal up on one side, and it will rotate out of the other side.  You can grab it with needle nose and pull it out.  Be sure to keep it against the crank, or you will really fight it trying to rotate it out of place.  One in the down position it will fall out. 

Lube the new seal with motor oil or assembly lube.  Place it against the bottom of the crank, and rotate it up into place on the top side of the crank.  Some seals come with a small plastic guide to stop the backside of the seal from scraping on the edge of the block and peeling part of the seal material.  If you guide the seal properly and use the guide like a shoehorn, the seal will go in easily.

Now retorque the mains, and then reinstall the rear main.   The reason to retorque the others first is to hold the crank in proper position, and allow the rear main cap to seat properly.  Torque the rear main, then install and torque the oil pump.   My 75 uses 80 ft lbs torque on the mains, and 65 ft lbs torque on the oil pump bolt.  Button up the pan and torque converter cover, reattach the steering link and fill the oil, and you are good to go.

Ken,
That was explained so well, I could picture the whole operation in my mind, with no problem. I even saw the little drops of oil falling off the crankshaft onto my glasses.

One trick you can use to keep the seal from leaking again, is , instead of aligning the ends of the two seal pieces flush with the block and main cap, turn the seals a little farther past flush. In other words, imagine the seal ends at 9 and 3 o'clock. If you offset the seals a little, say, 9:05 and 3:05, then the ends of the seals are no longer in line with the mating surfaces of the main-cap/block interface. It eliminates one source of a leak at that junction.
I know I'm not very good at 'splaining these things, but it does work! I wouldn't build a Chevy motor(2 piece seal type) without moving the seals like this.
Also, with the surfaces of the main-cap and the block clean, put a small amount of "Permatex Aviation Sealer" on these parts, where they fit together, and it will eliminate a possible source of leakage from the mating surfaces there.

Great explanations there Ken. Makes me wish I had done this last weekend while I was installing my rack and pinion setup. I had the perfect opporitunity with the old PS system out.  Now it may be a little bit harder to do. Also I like Adams tips about offsetting the seal and just a dab of sealant on the main cap. I will make sure to do both when I get around to this job. 

FYI,

The one piece rear main seals started I believe around 1987.