The Stovebolt Site Forums The Shop Area Driveline Need some help with 1946 transmission

I have an original 1946 Chevrolet 1/2 ton pickup in very good condition. I am a little puzzled on a few items relating to the transmission, that I am hoping someone on the forum can shed some light on.

1. The transmission has a serial number that identifies it as a 1946 3-speed manual, manufactured in Muncie, Indiana. Yet, it's case number stamping identifies it as a Saginaw 3-speed. The transmission has a reverse and 4 forward gears of which, #1 appears to be a granny gear. What do I have?

2. I have gear oil seepage from two places. One is the gasket area where the torque tube assembly bolts onto (with four bolts) to the transmission case (in the area of the u joint). The second is where the torque tube collar connects just to the rear of the transmission mount at the chassis crossbar.

I am trying to identify these gaskets both in type, part number and manufacture name...and also a source for getting these.

Any help would be appreciated.

If it has 4 forward gears, its a 4 speed. Does it have a lockout trigger for reverse. It is probably the GM corporate 4 speed sliding gear transmission that they used from around 1940 until mid year 1947. The numbers you are seeing are probably just casting numbers.

Hmmmmm.? From the shift description it appears to be a 4 speed. 1st would be granny low. Can't explain the number difference, but could it have been misread?
A 3 speed case would be different from a 4 speed and the master cylinder would mount different.
It appears the leaking seals need replaced. Check Jim Carter's truck Parts for Oakie bushings.

Reverse is in the LEFT-UP position of the shift pattern with no lockout. Then comes 1,2,3,4.

The serial number is stamped on top of the case behind the shifter. All other numbers are cast.

I have the same trans you do in my '46. What you need is a torque tube seal kit:

https://www.chevsofthe40s.com/shop/...case=&searchtype=FT&Seach=Search

You'll have to pull the U-joint apart to install.

http://s456.photobucket.com/user/blastenpene/media/46%20Chev/image14.jpg.html?sort=3&o=24

While you have the U-joint apart, check for play in the front of the driveshaft. If you have play, you probably need an Oakie bushing. Also give the U-joint a good looking over - frequently a source of vibration on these trucks when worn.

I would be interested in know more about this GM corporate sliding gear transmission.

Serial number verified, no misread. "DO110286. From what I can read, the "D" stands for 1946, "O" stands for 3 speed...produced at the Muncie, Indiana plant.

The transmission case has a casting number of 591195 with a 1946 casting date. That casting number should represent a 3 speed, yet mine is a reverse and 4 forward speeds. The case absolutely represents that of a 3 speed transmission.

All of the above is what has me confused?

Are the 3 speed and 4 speed transmissions produced in 1946 for Chevy trucks MUNCIES or SAGINAWS?
Do these tranny's have a name such as others (I.e. SM-420,etc)?

1946 transmissions
http://chevy.oldcarmanualproject.com/chevyresto/4649.htm

The 4-speed was an option on 1946 3100/3600
http://chevy.oldcarmanualproject.com/chevyresto/4689.htm

Thanks for the pages. I have read thru both and have come to the conclusion that I have a...

Muncie 318, optional 4 speed transmission, built in a Muncie 3 speed tranny case, which hold 1 1/2 pints of gear oil and looks just like all 3 speed transmissions.

Is this possible???

Sorry to keep beating a dead horse, but this is just not making any sense to me...

David...sent you a PM.

The case size alone, see the drawing shown for the 4 speed link above, is a good clue?

If reverse is left and then up towards dash (not down towards seat) and no lockout lever its definitely not the sliding gear 4 speed. Is the box you have synchronized? The sliding gear 4 speed boxes (also sometimes called crash boxes) are not synchronized. They also have straight-cut spur gears and have a noticeable "song" especially under a load in and in 1st, 2nd, and 3rd gears. Outward in appearance they are similar to the later SM-420 4 speed, but slightly smaller and shorter.

I posted this ride along a while back in the big bolt section, but it will give you an idea of what the sliding gear 4 speed sounds like. Turn up the volume for some gear whine!

Ride along.

It almost sounds like it might be a Clark 185F transmission. It was offered in GMC. I'm not sure if it was offered in Chev, but that doesn't mean that someone didn't replace the corporate sliding gear transmission with a Clark.

I don't think it's a Clark. Case does not match up.

Mine is synchronized and the case does not match up to the SM 420.

Enjoyed your video, TWICE!

That's what has me confused. I have a three speed case, but 4 forward gears and reverse.

My guess, this critter was buggered with over the years and the result is as it is now and the the numbers referenced are essentially meaningless to anything that rolled off any factory assembly line. If it all works, functions as you want and expect, great! Be happy and move on, if not then the goal quest is just beginning.

Don't mean to be mean or harsh or disagreeable, but that's how I see it. Best of luck!

It is very seldom that Chevrolet parts books refer to a casting number. However in this case, the parts book clearly states that a 591195 casting number is a 3 speed transmission 41-47 Commercial truck. The 1953 edition of the Hollander states the same thing.

https://plus.google.com/u/0/photos/...4758965010&oid=112636930370126476644

I find it rather hard to believe that someone put 4 speed gears in a 3 speed case. There is just not enough room in the small 3 speed case.

I have never seen one, but the parts book shows a 4 speed offered in 1935 passenger car. It was a model WT transmission. It is possible this is what has been put in your truck.

Well, it has been interesting at least to hear all the responses to my original question.

This all started because I wanted to make sure that I was identifying this tranny correctly for the purpose of ordering some replacement seals for the torque tube ball joint area. I have been told there are differences between the 3 and 4 speed, which makes sense.

Before asking the original question days ago, I too had look at all the pictures and specs between the 3 and 4 speed tranny's.

The cold hard fact is...that I have a 591195 case, with a serial number DO110286 stamped on the case and a January 1947 cast date. In addition, there are FOUR forward gears, with first being a granny gear and reverse is all the way to the left and forward towards the dash.

The transmission runs smooth as silk and I plan on keeping it a long time. I just wanted to verify it's nature, since these trucks are now so old and rare.

Moving forward, I will just order the seals/shims for a 3 speed case and move on.

Thanks to all for your opinions and suggestions.

Is it possible for you to post some pictures of this transmission?
I would sure like to see it.

Sent you a PM

I would also like to see a picture of this transmission.

Here is a LINK to Darling's mystery 4 speed transmission.
Sure looks like a 1937-47 3 speed case to me.
Now if we could just see inside

I didn't even get to see the outside of it. Looks like the link is broken.

Try it now.

It looks like the GM "peanut" transmission that was used from 37 to 47 as mentioned above.. It was so little, they had trouble squeezing 3 speeds into it. I wonder where they squeezed in the 4th one. Or maybe its the one us old drivers referred to as "Georgia overdrive". It was right in the middle of the shift pattern, and them old trucks would really go on a long down hill grade.

What I don't get is that it's synchronized in the top two gears. I though none of the 4 speeds before '48 had synchronizers. My shop manual only shows two transmissions: a sync 3 speed and a crashbox 4 speed.

I can't wrap my head around that 3 speed case having 4 forward gear in it. Are you certain that it has 4 forward gear--- as in you have driven this truck and actually used all 4 forward gears? Is it possible that something is broken internally and the mainshaft is binding on itself and giving the illusion of a 4th gear? I had my modern 5 speed Cummins powered transmission stick on me and act as if I had extra gears. It turned out to be the pilot bearing in the flywheel would bind sometimes and cause the input shaft to turn when it shouldn't be. I know that is a long shot with your 1946 3 speed case transmission, but I'm curious.

Also, on a totally different note, I've seen Chevrolet literature advertising heavy duty and light duty 4 speeds in the 1940's 3/4 tons. I wonder if this is one of those fabled light duty 4 speeds that I never seen in person? They did have light duty and heavy duty 3/4 tons for a while, so maybe.

Jason, I have the same problem imagining a four speed in that case. I have rebuilt many of those 3 speeds and those are a tight fit in that case.

It is my truck that I have had for 8 mos now. Yes, I drive it. It has a reverse in the far left, upward (toward dash) position. It has a 1st (actual GRANNY), 2nd, 3rd and 4th forward gears. 1st (up), 2nd (down), 3rd (up), 4th (down).

As I have stated before it is a 3 speed case (gm casting number 591195) and is stamped with a 3 speed serial number.

There is no doubt it is the correct 3 speed case.
As I stated above, I would sure like to see inside.

I looked through the parts book. Very few parts are listed for the illusive WT 4 speed. One of the few parts that I find is a 476041 shift lever which includes a reverse latch. So I guess that seems to rule out the 1935 WT 4 speed. A little more research in the 1953 edition of the Hollander indicates that the WT was actually a 4 speed Warner transmission used in trucks up to 1 1/2 ton. The Warner case is certainly much different than the GM "Peanut transmission".

my 46 1/2 ton has the Muncie 3 speed stamping - EO92051. That is correct, the serial number stamping indicates a 47 transmission. It is really a truck 3 spd with a roller bearing cluster gear. My casting numbers are similar on the drivers side of the case starting on the top
591195
GM 6
47
G288
The truck was built in December 46 so I guess they ran out of 46 transmissions. I am pretty certain this is the original.

But.. I really need some help with this one. When I disassembled there were not rollers left between the input and output shafts. So I need both. Does anyone know if the internals from a later model 3 speed like the 48 to 53 could be transplanted into the 47 case?