Oil Leak

[GeorgeHounslow]

Hi All,

I have found out that the cause of my rear axle oil leaks is engine oil leaking into the back axle and out one of the axle ends. I have followed the kind advice of several people on this forum regarding the installation of the inner neoprene seals - I have also fitted outer neoprene seals. I have been filling the U-Joint with grease on a regular basis.

It is my plan at the end of this season to pull the engine and rebuild it anyhow, with the 4th main oil leak being sorted - but was wondering if there is anything else I can do to prevent this happening in the meantime? Can the accessory felt seals be fitted along with the neoprene seals? Any help would be greatly appreciated.

Many Thanks
George

[JTT3]

George the plug in the driving plate shaft may be askew or missing, if it’s the 4th main wallowed out Gene French will bore a newly poured 4th main to the size of the driving plate shaft. Hope that helps. Best John

[speedytinc]

When you get into the the transmission, there is supposed to be a steel plug in the drive plate to keep oil from running out into the U -joint.
I dont know when this started. I am working on a fairly original 15 that didnt have the plug. Surprisingly with a sloppy 4th main & no transmission screen there was no oil washing away the U-joint grease.

4th main. If its badly worn it will pass a lot of oil, multiplied with an aftermarket oil screen. The screen dumps excess oil right on the 4th main lube hole. If the 4th main was machined centered, it can be turned 180 allowing less oil. 4th main issues can be addressed without pulling the motor completely or pulling back the rear end to access it.

Keep the engine oil level between the 2 petcocks.

If you have an early(pre 22 ish), high fill plug, keep the level well below the bottom of the axle tube. Grease level needs to be maintained @ the later axle plug level. On my rux I put a 1/4" drain plug where I want the grease level & a drain plug @ the bottom.

Are you sure your inner neoprene seals are still in tact & sealing?

[Jerry VanOoteghem]

George,

Really good seals will only hold in too much oil. What you need to do to get by, is to occasionally drain off the excess oil.

[Adam]

Many of these leaks are in part because the groove in some reproduction front driveshaft bushings are broached all the way thru instead of ending short of the rear of the bushing. The correct groove allows the front bushing grease to stay in place and creates a better seal. The bushings with the groove broached end to end allow more leakage.

[TXGOAT2]

Be sure you are not over-filling the crankcase with oil. Halfway between the lower and upper drain cocks is best. This usually takes between 3 and 31/2 quarts. Check oil with the engine warm and the car sitting on a level surface. Be sure both drain cocks are clear.

[GeorgeHounslow]

Many Thanks to all of you for your responses, I will make sure to check each of your suggestions in the coming week before I next go on a drive.

I have also now rotated the 4th main at someone else's kind suggestion, and that seems to be working so far today.

Thank you again for all your help.

George

[GeorgeHounslow]

Hi All,

I'm afraid the leak has returned after a long run, I had turned the 4th main 90 degrees, I have been running an oil screen, would any of you recommend removing the oil screen for the time being as I can hear this can be a contributing factor?

Many Thanks
George

[NoelChico]

Has anybody ever been able to machine or alter a 4th main to accept an oil seal without reverting to a ball or roller bearing?

[RVA23T]

I have a ball bearing 4th main that still had oil leak.
Mar 2023 I added an PTFE "oil slinger" large washer. What I bought is attached below, but I bought both the 1.562 ID and the 1.50 ID but do not remember which I actually used, and it has made a huge difference in leaking at the 4th main.

[speedytinc]

Has anybody ever been able to machine or alter a 4th main to accept an oil seal without reverting to a ball or roller bearing?

I have made bronze bushing 4th mains with an O ring.
A correct fitting babbit 4th main doesnt need one. The clearance should be .0015- .002" max.

[Allan]

When I do a rebuild I replace the usual domed plug in the output shaft with a cup type plug. It cannot skew and let oil pass.

Allan from down under.