VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Transmission is leaking after first drive

1941 Master Deluxe, 216 with 3 speed.

Transmission appeared to work well after the first 5 mile test run. There where no leaks prior to this. It appears that it is leaking somewhere after it was parked over night. Son saw this, cleaned the floor and dried it off to determine where it was coming from thinking that it would leak again, it has not restarted. Puddle under the car was a decent size (6 inches round). I probably would have done the same thing. It appeared to be from the rear or side of the transmission. Defiantly in front of the torque tube, The bell shaped part as my son says.

We know the car sat for 7 years minimum prior to us getting it and 3 before this drive. We have run the engine in the drive way without issue. I suspect the seals are dry. Unfortunately when we did our fluid changes I overlooked the transmission.

1. What fluid does this transmission take?
2. What is the best method to check it? Both for leaks and the fluid level?
3. Do we need to do anything other than open the lower plug to drain and use a pump to fill the upper hole? Saw a 48 done this way on YouTube. Not sure if the 41 and 48 are the same.

I use 85w-140 GL-5 gear lube in the transmission. There is such a low level of sulfur in gear lube today that it will not affect the brass synchronizers.

The drain and fill process is very similar to the ‘48. Just make sure you can remove the fill plug before you remove the drain plug. That can be problematic if you cannot remove the fill plug after you have drained the gear box.

It would not surprise me if the leakage is from the old cork seal around the bell.

If the transmission is overfilled there might be some leakage from around the input shaft. That would drip out the bottom of the lower flywheel cover. These transmissions use as slinger disc on the input shaft to manage the lubricant flow at the front of the transmission There is no seal on the front bearing.

The U joint ball seals are the most common area to leak

i think Chev called for an SAE 90 for your transmission in the summer and an SAE 80 in colder weather.
I use an SAE 80W-90 GL-5 gear oil in both the transmission and rear axle of my '46 truck.

But I see no problem with Rusty's recommendation of an 85W-140 either.
Either way, Rusty is also right regarding present day GL-5 oils being safe for your transmission.

Update, I have not checked the fluid and it has not leaked since the drive. Is it possible that it will only leak after being run?

Next few weeks are busy so it may be a bit to get the fluid checked. At that point where anything I do will bee a 1/2 hour here and there. Fluids are a job I do not want to take a chance of stopping and forgetting a step due to time.

I know it is time to add fluid to my transmission when it stops leaking!

You may have overfilled it. Use your pinkie and curve it down while incrementally getting near the fill hole. When you can just touch the oil, put the plug in. It is full enough. Recheck it every time you change the engines oil.

Oil from the transmission eventually drips out at the universal joint stuff or traces on down to the differential. That's why oil there is always full and even may need to bleed off until you can just touch it with the pinkie tool,

Oil wil trace along seeking the best and easiest gravitational route to drip off. Sometimes that point is not directly/plumb-bob below the leak/seep source.

Keep in mind that all the old 207s and 216s leak almost from the get-go. Those who have those engines may brag that their engine doesn't leak. They're pushing the envelope of honesty. Test them with this: "Would you be will ing to spread the missusse's wedding gown under the engine after it has run around the block a few times?" Or if she is available ask her: "Would you be willing to let him place that gown there for the test?" (Any positive answers will be a "tell" as to how well the marriage is coming along. Be sure to not make any comment positive or negative here.)

Best,

Charlie

Son changed the fluid. I am not the person to had him the tools. Also this way we do not need to jack up the car. Surprisingly easy. Both the fill and drain where properly tightened and came off easily. It was not empty but fluid was not up to the fill hole. About 3/4 a quart came out and a full quart went in. Filled it till it came out the top hole.

Plan for now is to watch for the leak and the fluid level. If it is minor we will top it off and keep it on the list of fix during winter. Just top it off every so often.

Only one issue. My set of 8pt sockets stops one size to small for the plugs on the transmission. Had to use a wrench. Ordered the socket. I have used the same socket wrench on every oil change since I started driving. The handle is short enough to make it difficult to over tighten the plug.

Helpful discussion for me as I have a leaky transmission and have been topping it up periodically.....until the gear oil starts to come out of the fil hole. Will now use pinky to avoid overfill. I use a piece of wire coat hanger as a type of dip stick through the full hole to help judge when it is time for a top up. Whether pinky on the fill or coat hanger on the low level I'll still be guessing....but at least topping fairly easy with not having to jack the car. Thoughts on the following?

- On my coat hanger dip stick, how far below the fill hole would you feel comfortable before proceeding to refill?
- While fluid may be escaping from a number of places, I can see oil dripping from the sift linkage cover on the driver's side of the trans. Can this gasket be changed without removing the trans?

Thanks.

I'd say at least half an inch.

Yes. but hard to not mess up the shifters so after cleaning the surfaces it will go right back in so all you have is tighten the bolts and reattach the linkage.

You can use the cover to outline the space needed for the gasket and use a light ball-pen hammer to make the bolt holes on a new piece of gasket material.

Someone else may offer their advice on thickness of the gasket material. Sort of light to medium, I expect.

Good luck with it.

Best,

Charlie

Thanks Charlie. Sounds like maybe I've been waiting too long to refill. I wait unti it's about 1.5 inches below the hole...sometimes more.

Also, could you say a bit more on messing up the shifters and how to deal with that as I didn't understand fully.

The shifter forks have to be in the correct position when you install the cover. The fork have to slide into the shift collars.

For example if the transmission is in neutral when you remove the cover, the shifter arms and forks have to be in the neutral position when you install the cover.

The tricky part that sometimes the cover will install fine with the fork out of position. It is just sticking inside the transmission around the gear drum. You will not discover the problem until you try to shift the transmission.

It is easy to knock one of the shifters to a different detent when you are cleaning and handling the cover. If you need to remove the shifter arms to replace the seals on them it is pretty easy to have them out of position..

Like Charlie suggested about half inch below level with the fill plug hole and top up to just coming out the fill plug hole.
Tony

I guess we over filled it slightly then. We filled it till it came out the top plug, level with the bottom of it. That was the way they did it in the video we saw on a 48 Chevy 3 speed.

How much should the transmission hold? We drained it and a full quart was all it took.

1 1/2 pints.If it is over filled just remove the top plug and any excess will drain out. Then you will have the correct level according to the shop manual.

Thanks Rusty, very interesting.

What gear position would you suggest is the best starting point before removing the cover to help avoid the problem...or does it matter?

Is there a way to check that shifter arms and forks are in the right position before the cover goes back on?

I suggest that you put the transmission in neutral before removing the cover.

When you have the cover removed you can see how the arms work and feel the detents as you move the arms. Each arm will have 3 positions. Just make sure both arms are in the middle position when you install the cover.

Snug the bolts to locate the cover. Then move each arm as though you were shifting the transmission. If you cannot select all 4 gears (3 froward and reverse) then something did not assemble correctly.

Remember that there is an interlock device between the 2 arms to prevent the transmission from being shifted into 2 gears at the same time.

Much appreciated, many thanks.

Drove the car again and the level is just below the fill hole. Leak is now vary minimal.

Ok the leak is getting worse. It only leaks after running. A few drives and it needs s refill. Looks to be coming out the back of the transmission. There is slight evidence on seepage around the linkage but nothing I would call in need of repair there (only see it due to dirt build up on the side). Looks ok around the bell housing.

What seals are needed for the rear of the transmission? I have never done this job before, is this a night, weekend or down for a while type job for a first timer? I am asking because if this is a weekend task we may fix it now. If this is a down for a while task it may be a but on the winter list task.

The winter list is growing. After four years of waiting we do want to drive the car and enjoy it even if it requires filling the transmission every couple of drives.

Look at this. You can skip the first half, about the bushing and watch the second half about the seal.
https://www.chevsofthe40s.com/detai...Ball_Seal_Kit_For_Drive_Line_Manual.html

It will most likely leak somewhere regardless.

Thanks for that video. I was afraid I was going to have to replace a seal in the transmission. It looks as if I should do the following then:

1. Check that the bolts are tight at the front of the torque tube ball (Video said that could cause it to leak. Cannot hurt to check the simplest thing first).

If / when that fails:

2. Remove the trunnions and then the ball to replace all of the shims and seals.

The ball needs to be cleaned and smooth to ensure a good seal. I typically polish then with 400 wet paper.

This trick will save you time and frustration. When you re-install the bell shield retainer install more gaskets rather then only a few. Then you can just tear away a gasket at a time to make the retainer snugly fit the bell.

Before you install the retainer and bell trial fit them with the new seal. For the last one I did the seal was way too thick. I had to reduce the thickness quite a bit by sanding it on 60 grit sandpaper.

A little more good info about the "ball" in this clip.

Sometime ago I read a post on here where replacing the thicker cork seal with a "O" ring or 2, I cant comment on actual success but may well be better than cork.
Tony