Rear Main Leak - Anybody Milled the Seal Cap?

[Mebsuta]

When I got my RR, it still had the original drive train. The only thing that wasn't leaking was the rear main with the rope seal.

One of these days I have to under there and put in another one, or else there is no point in replacing the slipping clutch, because it will just get wet again.

I'm afraid of working under the car now though, and keep putting it off. I might let somebody with a lift do it.

 

[wyrmrider]

Those work or you can modify a stock bearing
Mopar Performance used to sell them and others

 

[not so famous bob]

Milling the cap does 2 things. Most builders don't think about the second. It tightens the bottom half of the seal but it also pushes the top half of the seal away from the crank.

makes it harder to seal at the gasket surface, ask me how I know !

 

[Challenger340]

Next time you put the seal in have a look at "this", and MUCH easier to see with the Engine on an Engine stand.
1.) Put upper main seal half in "flush" with Block parting line
2.) Install Crankshaft(no main caps)
3.) Now look down at the main seal "lips" in contact with the Crank
4.) SEE the problem ?????????????????????????????????????????

BB Mopar upper Main Seal grooves are NOT CONCENTRIC with the Main Line, so you will SEE one side of the Lip seal is in Contact with the Crank MORE than the other side.
Usually, it is the Passenger side that is barely touching/sealing against the Crank = drip..... drip.... drip !

Remember here, ALL factory BB Mopars used ROPE seals ? so the groove NOT being concentric with the Crank centerline was no issue, the rope just swelled up with Oil on the looser side and sealed anyways.
But Today...
using a Neoprene style 'lip" seal, close attention must be paid to correct installation.
NO 007, Billet, top secret sh*t whiz bang retainer system will compensate.... nor is it req'd, IMO, just a waste of MONEY !
I put a sticky over here on how to install a neoprene Main Seal when you SEE the problem
http://www.forbbodiesonly.com/mopar...d-on-rear-main-seal-replacement.127618/page-2

 

[PurpleBeeper]

Well, here's an update:
1. 2nd rear main seal (2-piece) --> I had installed the top half only backwards (lip facing transmission).
2. While in there, I re-sealed the two galley plugs with a 2-part Teflon paste (activator spray + tube of telfon)
3. Turning the oil pump with the transmission out, there was no doubt at all that the rear main seal was the problem.
4. I did buy a "whiz bang" seal holder (maybe a waste of money) and used the high-dollar seals (crank + sides) and used assembly lube, checked clearances with caliper (hard to do, block/crank interference) + shims (not much use, my math must have been way off).
5. Transmission still not back in since Jegs sent me the wrong clutch disc... or I clicked on the wrong one since non-Mopar discs come up on the search page right beneath the Mopar ones, even when you search 70 Road Runner

 

[lewtot184]

bet that top half in backwards was the majority of your issues.

 

[Gold Rush]

Next time you put the seal in have a look at "this", and MUCH easier to see with the Engine on an Engine stand.
1.) Put upper main seal half in "flush" with Block parting line
2.) Install Crankshaft(no main caps)
3.) Now look down at the main seal "lips" in contact with the Crank
4.) SEE the problem ?????????????????????????????????????????

BB Mopar upper Main Seal grooves are NOT CONCENTRIC with the Main Line, so you will SEE one side of the Lip seal is in Contact with the Crank MORE than the other side.
Usually, it is the Passenger side that is barely touching/sealing against the Crank = drip..... drip.... drip !

Remember here, ALL factory BB Mopars used ROPE seals ? so the groove NOT being concentric with the Crank centerline was no issue, the rope just swelled up with Oil on the looser side and sealed anyways.
But Today...
using a Neoprene style 'lip" seal, close attention must be paid to correct installation.
NO 007, Billet, top secret sh*t whiz bang retainer system will compensate.... nor is it req'd, IMO, just a waste of MONEY !
I put a sticky over here on how to install a neoprene Main Seal when you SEE the problem
http://www.forbbodiesonly.com/mopar...d-on-rear-main-seal-replacement.127618/page-2

This is EXACTLY what I found! Probably the main cause for most rear main seal horror stories I've read about.

I've had the 400 back in my '74 SE for a few months. Imagine my disappointment when the dreaded DRIP immediately showed up! Have spent the past few months soaking up as much information I could find and decided to try a different seal. The first set I installed was FELPRO BS40240 and it was obvious that one side was not sealing when I remove the rear seal retainer. The second seal set I just finished installing is Mr. GASKET P/N 1968.

I could tell just by close examination the Mr. GASKET sealing lips were more substantial but remembering the difficulty I had getting the retainer in place with the side seals really cause me concern. The Mr. GASKET side seals are not stiff like the FELPRO ones. These were soft so I was worried they might get damage during installation. In reality these soft seals may have made the installation easier.

Getting the old top seal out was more difficult than I thought it would be but putting the new one in was actually easier. I shot a liberal amount of assembly lube into the upper channel then carefully rotated the upper seal half around making sure to keep inward pressure to prevent seal damage. Next came the side and lower seals. Both were fitted into the retainer and the main seal given a healthy coat of assembly lube. I put a very light film of the same lube on the side seal and the inside of the engine block mating surface. I very slowly worked the retainer up into place using clean and dry paper towel to help me keep the side seal in place. First time I didn't get it right but the second try was perfect. All assembly completed and engine now has over four hours of run time without a single drip!!!!

 

[PurpleBeeper]

Next time you put the seal in have a look at "this", and MUCH easier to see with the Engine on an Engine stand.
1.) Put upper main seal half in "flush" with Block parting line
2.) Install Crankshaft(no main caps)
3.) Now look down at the main seal "lips" in contact with the Crank
4.) SEE the problem ?????????????????????????????????????????

BB Mopar upper Main Seal grooves are NOT CONCENTRIC with the Main Line, so you will SEE one side of the Lip seal is in Contact with the Crank MORE than the other side.
Usually, it is the Passenger side that is barely touching/sealing against the Crank = drip..... drip.... drip !

Remember here, ALL factory BB Mopars used ROPE seals ? so the groove NOT being concentric with the Crank centerline was no issue, the rope just swelled up with Oil on the looser side and sealed anyways.
But Today...
using a Neoprene style 'lip" seal, close attention must be paid to correct installation.
NO 007, Billet, top secret sh*t whiz bang retainer system will compensate.... nor is it req'd, IMO, just a waste of MONEY !
I put a sticky over here on how to install a neoprene Main Seal when you SEE the problem
http://www.forbbodiesonly.com/mopar...d-on-rear-main-seal-replacement.127618/page-2

Well, I don't remember my engine gushing oil 20 yrs. ago & I HOPE this isn't my problem since the engine is in the car. If this seal leaks, then I guess my only hope is to see if I can still find a rope seal available somewhere and use one of those "Chinese finger lock" tools to install it. I did that once a long time ago on a "brand x" car. Wish me luck gentlemen. I would like to get a good run in before the snow.

 

[Gold Rush]

Well, I don't remember my engine gushing oil 20 yrs. ago & I HOPE this isn't my problem since the engine is in the car. If this seal leaks, then I guess my only hope is to see if I can still find a rope seal available somewhere and use one of those "Chinese finger lock" tools to install it. I did that once a long time ago on a "brand x" car. Wish me luck gentlemen. I would like to get a good run in before the snow.

See post above yours... I've been building engines for over 60 years and this was the first rear main I ever had leak from a new rebuild. Finding the thread about the misalignment was a real score! All I had to do then was find a cure. I believe the Mr. Gasket #1968 is the key and it was MUCH easier to do than rope.