rear main , old topic but here we go.

old ugly

old ugly

Well-known member
1928 model A
i changed the rear main seal, i used the aftermarket brass thrust/seal, i have .003" endplay.
the mating surfaces were all level.
the bearing clearance is .0015"-.002"
there is about 3 shims on each side. ( i don't remember how thick)
the drain tube is free from obstruction.

i have a oil dripping out the cotter pin hole, no leaks outside the bell housing.
i can see in there , sort of, with the inspection plate off and it is the rear main leaking.

questions
-should i have ran sealer around the edge of the bearing mating surfaces during assembly?
-is there another reason this should drip?
-how much do they normally drip?(maybe a silly question)

thanks for any help on this.
ou
tom
 
Set the oil level just above the add mark and see if that helps. Sometimes they have a little to high of an oil level.
 
Are the top edges of the seal absolutely flat with the bearing mating surface? If any part of the seal is "standing proud" of the surrounding bearing mating surface, it will not allow the bearing cap to properly mate upon bolt up, leaving a far-to-wide clearance. That will leak like the Exxon Valdez! I have an engine to work on that the previous owner hammered in one of those bronze seals with the "standing proud" condition. I plan to remove the seal and rebabbitt the block properly.
 
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Good advice above. Plus, I think .0015" is bit too much clearance for the rear main.

You are sure the bellhousing has a gasket ?
 
I think .0015 is about as tight as you should set the clearance. 1 1/2 thousandths. Any tighter and the bearing might burn.
 
the surfaces are as flat as i could make them.
the oil is definitely coming from the rear main

IMG_4876.jpg
 
I would expect some oil exited the rear main even when the model A was a new car. It would depend on how much is leaking.
 
i did a long drive today got it good and warmed up, it drips about 1 drip per second. i guess it will have to come apart to see what i messed up.
thanks
ou
tom
 
When you assembled it, did you put a dob of silicone in the corners where the sump (pan) gasket meet the cap?
 
if the transmission leaks at the front will the oil run out the cotter pin hole?
i can't tell the color difference but the oil feels stickier
thanks for helping here
ou
tom
 
.0015" is good for all the bearings as far as I'm concerned. Except I like the rear a bit tighter. .0012" just a tad tighter. I think if the rear main is leaking then there is something else wrong.

I kinda learned the hard way a long time ago to run rear mains a bit tighter on other engines. I was breaking too many cranks at the flange until I tightened them up, I was concerned about ruining those bearings, but, they ran fine.
 
i am now thinking i have ****** oil leaking into the bell housing. somehow.
it was full before a 15mile drive and now it is down by one knuckle (baby finger)
never the less i think it has to come apart again.
when it comes apart i will recheck the clearance on the mains.

thanks everyone for helping.

ou
tom
 
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To identify which wipe everything off, take it for a drive, then go to a clean spot in the garage and leave it run and drip., Dap it with your finger. To me, that 600W trans oil always smells way different!

The shimming you have checked, the engine is still in the car for this, right?
 
Gene F said:
To identify which wipe everything off, take it for a drive, then go to a clean spot in the garage and leave it run and drip., Dap it with your finger. To me, that 600W trans oil always smells way different!

The shimming you have checked, the engine is still in the car for this, right?
Click to expand...

yup the engine is in the car.
the color, smell and texture are different ,two different leaks, i have an engine leak and ****** leak. i just have to determine how bad the engine leak is because if it is just slight drip ill leave it and pull the ****** by pulling the rear end back.
thats the next test.
i think the engine leak is minimal so to test im going to let it run at a high idle on the shop floor and see how much oil come out.
then i will drive it a bit and see how much ****** oil dumps out on the floor.

i have always taken the ****** out by pulling the motor but i suspect it less work to pull the rear end back.

thank you
ou
tom
 
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