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37 Rear Main Seal


bayo-wolf
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I've developed a leak in the rear seal. I've got a bearing going out in 1st gear, so I needed to drop the transmission off anyway. I was going to live with the 1st gear problem for awhile, but the leak is bad enough to make the clutch slip. So now I need to go ahead and drop it off. So it shouldn't be too big a deal to change the seal out then. Are there any big issues here that relate to V12s?

Shawn

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Couple of things come to mind. First, is the leak coming from the back of the engine or the front of transmission? If it's coming from the engine, then it might be that the cork seal on the oil pan is not holding (what I think I have). If it's really the rear main seal, then there will be more work to replace it.

If the leak is coming from the tranny, be aware that originally the '37 Zephyr transmission did not have a oil seal (like later trannies), but a slinger-style arrangement. You would be wise to update to a later version setup at this time -- if I recall, you'll need the newer style bearing cover and an oil seal, but it's a simple bolt-on conversion.

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I didn't think about the pan gasket. I think the leak is definitely coming from the back of the engine, not the transmission. I'll have to remove the cowling at the back of the pan to be sure. It is maining dripping out through the cotter pin hole in the bottom of the cowling.

My first road trip with it was about 30 miles and I got a lot of leaking from this position. I lost about a half quart of engine oil.

Second trip, also about 30 miles and the leak had dropped off a lot. Do you think the cork gasket might have been dried out and expanded back to slow the leak?

Previously I had run the engine in the garage, loaded it on the trailer, etc. This was my first highway trip though.

Shawn

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Shawn, the possibility no one has cared to mention yet, is that the excessive oil is coming out of the rear main bearing, this usually happens in hi-mileage engines that have developed end play, and the "slinger" type oil seal is no longer effective, you can check for end play by grasping the fan from the front, and pshing and pulling it fore and aft, if you detect movement, you have end play, and probally need new bearings and a crank grind, no E-P, good, then return to the cork seal program, good luck

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A few things to look for when you check the cork seal. Hopefully that'll be the problem but check the S-shaped drain tube on the rear main for blockage. Any blockage will cause the oil to build up in the slinger area and leak out.

Other remote possibilities could be a leak around the oil pump idler gear housing on the back of the block or even a damaged/cracked slinger seal housing half. You would have to remove the flywheel in order to check these areas. One member in the club actually discovered a piece broken out of the slinger seal housing on his '36. The flywheel can be removed after the pan is off if you think you need to check those areas.

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Mike, that drain tube has a captive ball check and allows oil to drain from the slinger area back into the pan. The ball check will keep oil from flowing back up the tube. As the slinger area is "open" oil could flow out of the pan if the car was parked on a steep hill. While the tube is fairly large it can't handle the flow when the rear main wears to point that the oil flow overcomes the capacity of the slinger and drain tube. Dee

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