Trans Oil Leak

John S

John S

Senior Member
I am working on a '28 roadster that we bought from an estate sale a few years ago. The car was apart for paint when we bought it and is a complete unknown. It was restored in the late '60s and seems to run and drive like it should but other than that, I don't know anything about it. The re-assembly has progressed to the short drive "shakedown" stage and of course that's when the bugs start showing up.
And this bug I've never seen before.
After a drive of any length, it will leak about 5 tablespoons of trans oil out of the speedo cable housing and drive gear case adapter on the torque tube. The trans is dry other than that. When we first got the car it would leak oil from the trans just sitting but I never looked to see where it was coming from. I'm thinking the slinger was left out when the trans was put together but I don't know. I do know that I want some input from you all as to what to look for before I tear it down.
 
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There is a 3/16 vent hole located about half way up the back of the shift tower on the transmission top. If this vent is blocked with dirt and paint it will cause a leak. if you don't find this vent hole that means that it is blocked and painted over. Usually when the vent is blocked the leak will be worse than you describe, so this may or may not be the problem, I just thought it may be worth looking at.
 
If the rear oil baffle was left out, oil is going to migrate past the rear ball bearing in the trans and into the U-joint housing and on into the torque tube roller bearing area where the speedo housing is. Another possibility is that the bolt that holds the U-joint to the rear of the main shaft has come loose and backed off. There should be a special washer under it with a little "grabber" that grabs one of the spline elements of the main shaft. If the U-joint is loose on the spline it allows the rear ball bearing in the trans to drift away from its stops and will allow oil to pour through.

Unfortunately to correct either of these issues you have to pull the trans. When rebuilding a trans there are a number of things you can do to prevent oil leaks. You can purchase the front and rear ball bearings that are sealed. I remove the seal from the inboard side of both bearings so they can be lubricated by the oil. You can also purchase cluster and idler shafts that have been machined and fitted with O-rings. Leakage around the rear of both these shafts is very common otherwise.

For sure check that the vent hole is not plugged. It is on the tower just above the floor boards.

Also check that the proper oil is in the trans. The very thick oil that approximates the original 600W may slow down the leak. The 600W currently on the market varies with each supplier. I prefer the oil Bratton's offers. It is very thick and has a small percentage of STP in it. It clings very well to the main shaft and does not foam as many other oils do.

Tom Endy
 
I just checked the vent and it's open. I don't have a clue what oil is in it but it looks like 90 or so. The way this thing is leaking you could put roofing tar in there and still get a few drips.
There very well could be something loose in the u-joint area but there are no abnormal noises or vibrations and very little oil around the clams. The trans in this car works like it should execpt the leak. I guess I'll pull the shifter and see what I can see.
If the rear end and torque tube were pulled would it not be possible to remove the rear bearing retainer and replace the rear bearing without removing the trans?
 
Just pulled the shift tower and the good news is the gears look like new and the front bearing is the sealed type.
The bad news is there is no oil baffle in front of the rear bearing. I guess I'll pull the rear end and install a modern bearing and seal like Tom Endy said. I just got done overhauling the trans in my coupe 2 weeks ago and I didn't want to do another one any time soon. I can't think of a tougher job on an A than remove and replace the trans. Oh well, at least it's only a bearing.
 
Though I have never done it, I believe you can accomplish the task as you asked, by pulling the rear end and only pulling the rear of the trans apart.

You will need to remove the U-joint. make sure you have the proper lock washer and flat washer with the grabber on it. Look at the hex end of the bolt to see if there are witness marks of it from being hammered by the end of the drive shaft. You will then need to remove the safety wire and the four bolts holding the rear bearing retainer. Pull the main shaft out of the housing. The two slider gears will fall off, so you need to have the tower off to put them back on. You will most likely need to press the old bearing off the mainshaft and press the new one on.

Even with a sealed bearing you should install the oil baffle to maintain proper clearances. Be sure you install the correct one. There are two sizes. Henry did this to confuse and confound the next hundred years of Model A owners. The size depends on which housing you have. It is all covered in the service bullitens. If you find that the bearing stop is machined into the housing, this is the early housing and requires the smaller diameter baffle. If there is a snap ring there as a stop, this is the later housing and requires the larger diameter baffle. The difference in baffle diameter is so small you almost need both to compare. But beware, if you put the larger baffle in a housing with the machined stop you will jam the trans when you bolt the rear bearing retainer back on.

Supplers only sell the larger diameter baffle. If you cannot find an original early small one you can clamp the larger in a drill press and file the diameter down to fit.

I remove the inboard seal on both sealed ball bearings. This way the bearing elements will receive lubrication from the trans oil. Some suggest leaving both seals in place to keep contaminates out of the bearing. Your choice.

When you re-assemble make sure the small roller bearing up inside the input shaft is in place. Slide the mainshaft into the housing and put the two sliders back on. Make sure the shifting slots are facing each other.

Good luck with the project,
Tom Endy
 
i had a speedo gear leak . it was the gear shaft . thru it away & put another in & no problems ..............
 
Thanks for all the replies. Now all I have to do is fix it.:eek: I'm going to pull the motor in this car soon to tear it down and look it over before I really start driving it.
As hokey as the restoration is on this car I'll go ahead and pull the rear and fix the trans now. That will give me a chance to check out everything from front to back before I really put it on the road.
 
Tom, do you know of an exploded view that shows the location of the special washer with the grabber that you describe? I just put a rebuilt trans in my Tudor, but I don't remember anything like that. We didn't remove the U-joint, the trans came out with the engine, and the U-joint stayed on the drive shaft.
 
Look in Bratton's catalog on page 46, shows an exploded view of the trans with U-joint. Item 34 is the special washer. On page 47 is part number 10430, which is the bolt, lock washer, and "special tabbed washer". The text of the part number describes how it should be installed. If you don't have a catalog call 800-255-1929 and Bratton will send you one free of charge.

Tom Endy
 
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