So I replaced trans, flywheel, clutch and pressure plate and while I was there I replaced the rear main seal. I noticed it leaking very little over the pasted week then I took it for 350 mile round trip and its leaking bad now. Got new seal and going to do it again, any tricks to the trade here? I know the front seal has a sleeve to install but nothing on the rear?
I thought I would grease it up this time.

Which type seal did you use, rubber or teflon? The teflon one goes on dry. The biggest issue with a rear main seal is getting the retainer centered with the crank, block and oil pan. Take a few extra bolts out of the pan near the back for some clearance for the retainer. Use a couple of screw drivers between the block and pan to get some clearance. Then let the crank center the seal/retainer, you will need to make sure the bottom of the retainer is square with the pan. 

 

The real early industrial blocks had dowel pins for the retainer, they were self-centering.

I bought the Felpro gasket which feels like rubber, would the teflon be better?

 

Does the crank have groves from where the old seal rode? If so that is not helping the case. Can install a sleeve over it. 

 

It is most likely a rubber (Buna-N) seal that you bought. They work well overall. Viton would be an upgrade.

 

Teflon (PTFE) has less resistance but has a tendency to get a memory to it. You shouldn't have issues with it in Texas.

 

 

Side note, a leaking rear main can cause the clutch to slip.

11 hours ago, That Guy said:

Side note, a leaking rear main can cause the clutch to slip.

Even with a #5 injector line leaking will make a clutch slip.

 

I'm watching and learning because someday I know I'll find a guy that needs a crank seal next. Matter of fact I should dive into that Ford 7.3L and do a crank seal.

Edited November 13, 20204 yr by Mopar1973Man

Up date - rear main is dry as a powder house, new transmission front seal leaking. Pulled trans got it out on the bench investigated a little closer and input shaft bearing has wear marks on race and bearings. Called powertrain products and they seem to be ready to send a new trans, will know more after they look at pics. 
Trans has a lot of metal or aluminum shaving in it. 500 miles on this trans. This is my luck. Will keep you up dated. 

That's a lot of work doing it twice. Makes you wonder what happened and how many transmissions they have rebuilt. The NV4500  is pretty simple to put together not like some other brands that need duct tape, fishing string and anti gravity to get back together. 

I've seen fee videos on nv5600 and feel pretty confident that I can do it, looks straight forward to me. I'm actually rebuilding np200 right now just to exercise my brain, had it for 15 years. Got 2 of them when building my mud truck never blew the first one up so I still have it. Tore it apart and it's actually all brand new inside aside from bearings are seized up and yolks are shot. This must have been a military surplus unit that never got used. 

What a mess... Wow! Fresh bearing and a lot of clean up I don't see why it wouldn't work. Cleaning is going to be the biggest time sink.

2 hours ago, Mopar1973Man said:

What a mess... Wow! Fresh bearing and a lot of clean up I don't see why it wouldn't work. Cleaning is going to be the biggest time sink.

I think it's been outside for decades before I bought it 15 years ago, been in the garage since but moisture took its toll. All the gears are cleaning up nice just need some bearings and seals. All of the important pieces are in great shape. Not sure what I'll do if it's yet, may just assemble it back together with some grease packed all over and put it back under the shelf or sell it as parts, don't really feel like buying a bunch of stuff for something I probably won't use.