303M HydraMatic rebuild

[rustystud]

So, looking at making a kit for the reduction unit. With that in mind, this is a list of gaskets that would be needed....
1. Accumulator cover gasket
2. Reduction unit case halves
3. Lower valve body gasket(reduction)
4. Upper Valve body gasket(reduction)
5. Transmission to front reduction unit case half
6. "BB" pump gasket housing gasket

Did I miss anything? I don't want to tear down one of my cores to recover "BB". I will dig through some parts plowboy gasket me and see with luck if there is the mystical "BB"

Funny that you posted this today.
This morning, I just recovered four gaskets in almost perfect condition from my other reduction unit and made a template of the large gasket using craft paper and some roll-on ink.
That "BB" gasket is for the rear pump unit.
There are three gaskets on the reduction units control valve assembly alone. Then there is the rear pump gasket ( The "BB" gasket) then the large main body gasket. So, including the "special" rear main housing gasket that makes six gaskets needed in the reduction unit. I have several rear oil seals from "Timken" coming in soon too. The Timken seal is #416273 .
This upcoming week I'll take these gaskets down into Seattle where there is a gasket specialty company that says they will make "one off" gaskets.
So that just leaves the metal seal rings and piston lip seals. I can reuse some of my lip seals and I have some pretty good seal rings. It would just be nice to find someone who actually has these items new.
Then a proper kit could be made up.
There used to be a really good transmission parts supplier in downtown Seattle by Boeing that had all makes and models of transmission parts. I could have taken the metal seal rings down there and found some that would match. Maybe a center seal ring from a Ford C-6 would fit one of the reduction units. Who knows !?!? You just need a large selection of rings to go through to find a match.
I only have a few parts left from my rebuilding days. Sadly I threw out boxes of TH400 parts last year. I had no room to store them anymore. I even throughout four Chevrolet TH400 cases too. My friend got miffed that I didn't tell him about that. My take on that was if he had come around more often, he would have seen what I was doing. Plus I didn't know he wanted TH400 parts. I did give him several 5 gallon buckets full of parts though.

 

[rustystud]

Took care of a few small projects today.
One was replacing the oil drain pan plugs with nice stainless-steel ones.
I had to use a 3/4" pipe tap and cut down almost to the end of the tap. Then I used a 3/4" "straight" pipe tap to finish out the hole threads.
The new plugs had a "Straight" thread instead of a "Taper" .
The plugs look real nice and they will never rust to the pan.

 

[rustystud]

Surprise !
I found six NOS bands yesterday. Four front bands and two rear bands. I got these back when I was working at the surplus shop. Too bad I didn't get more rear bands.



I also found eighteen NOS "selective" thrust-washers .
I'm missing a #1 and a #5 thrust-washer to have a complete set. I do have a bunch of #3's though.

 

[rustystud]

Here's the gaskets I will try and have made up.

 

[rustystud]

On another little modification I'm trying, is replacing the front servo with a 1953 model HydraMatic.
This servo has a really neat little valve built in called the "overrun control valve" .
This valve prevents the front band from slipping when descending grades when the transmission is in 3rd gear thus providing " engine braking" !!!
You ask how is this possible ? This valve allows "mainline" pressure to the front servo "compensator" when normally the compensator pressure is low due to high "Governor" pressure (road speed above 20 MPH) .
Here's a picture of the "normal" front servo.

Here's a picture of the front servo with the "special" valve.
So far I can find no reason it should not work in our 303M transmission.

 

[DUUANE]

What a great write up Mr.Studly.

Fantastic info. Thanks for sharing.

Cheers

 

[1944mb]

Here's the gaskets I will try and have made up.
View attachment 926394View attachment 926395

Rusty, so would be willing to have multiple gasket sets made? If not could I have you send me a reduction unit pump gasket? I have two of the three reduction unit valve body gaskets, but must've missed the third. Although, I have not had time to tinker with my core till after dark, I am bound to miss something. Looks like you are missing the accumulator gasket yet for the reduction unit. This is what I currently have for a gasket kit for the 303M--
Reduction unit--
3 valve body gaskets
accumulator top gasket
reduction unit case half gasket
transmission to reduction case gasket
Main transmission gaskets--
filler cap gasket
filler spout flange gasket
"pan" gasket
side cover gasket
cooler pan cleanout
torus cover gasket
crank-flywheel gasket

LPcoatings and I have been communicating off the air and I was going to get him a complete gasket kit to replicate. His company, or one he works for manufactures the m151 body panels. http://www.m151bodypanels.com/ T'would appear they must good manufacturing capabilities.

I would like to continue to work on actually have a "kit" for the 303M rather then buying something that has half of what you need and have of what you don't. something like the following:
Gaskets
Seals
Frictions/steels
Bushing/thrust washers

Not sure if anyone would be interested in them, or in what capacity they could be re-produced, but if nothing else I'd out half a dozen on my shelf for future endeavors. Even if someone didn't possess the capability to overhaul one, they'd have a complete kit to take to someone who could. Could you send me a spare rear pump gasket, and rear valve body gasket(i will have to look at the two I have and see which one I am missing).?

Also on the thrust washers do you have part numbers where a person could put a part number list together?

 

[1944mb]

And yes throwing TH400 transmissions away would be sinful

 

[rustystud]

And yes throwing TH400 transmissions away would be sinful

I know, I know . I feel really bad about that. I just have no room !
I'm about to have even less room once the old shipping container is gone. I promised my wife I would get rid of it once the shop was built. That was 4 years ago now. The problem is I had to settle for a much smaller shop due to the "#@#$%%$##" permitting department here in King County. Seems there is a stream near my property that feeds another stream that has in the past supported Salmon. So, building a larger shop would somehow endanger these Mythical Salmon. Now I have very limited storage space.

 

[rustystud]

Rusty, so would be willing to have multiple gasket sets made? If not could I have you send me a reduction unit pump gasket? I have two of the three reduction unit valve body gaskets, but must've missed the third. Although, I have not had time to tinker with my core till after dark, I am bound to miss something. Looks like you are missing the accumulator gasket yet for the reduction unit. This is what I currently have for a gasket kit for the 303M--
Reduction unit--
3 valve body gaskets
accumulator top gasket
reduction unit case half gasket
transmission to reduction case gasket
Main transmission gaskets--
filler cap gasket
filler spout flange gasket
"pan" gasket
side cover gasket
cooler pan cleanout
torus cover gasket
crank-flywheel gasket

LPcoatings and I have been communicating off the air and I was going to get him a complete gasket kit to replicate. His company, or one he works for manufactures the m151 body panels. http://www.m151bodypanels.com/ T'would appear they must good manufacturing capabilities.

I would like to continue to work on actually have a "kit" for the 303M rather then buying something that has half of what you need and have of what you don't. something like the following:
Gaskets
Seals
Frictions/steels
Bushing/thrust washers

Not sure if anyone would be interested in them, or in what capacity they could be re-produced, but if nothing else I'd out half a dozen on my shelf for future endeavors. Even if someone didn't possess the capability to overhaul one, they'd have a complete kit to take to someone who could. Could you send me a spare rear pump gasket, and rear valve body gasket(i will have to look at the two I have and see which one I am missing).?

Also on the thrust washers do you have part numbers where a person could put a part number list together?

The gasket company I'll try and have make up the gaskets needs a "minimum" order. So there should be extras left after I keep what I want.
About the thrust-washers, they are standard HydraMatic parts. Any 1940 to 1956 HydraMatic will have the same thrust-washers. So any repair book would show the same part number. Sadly that won't do you much good as these parts are no longer made. I should clarify that statement. Fatsco is repoping these thrust-washers I believe. I need to give them a call again and ask about some bushings.

 

[rustystud]

What a great write up Mr.Studly.

Fantastic info. Thanks for sharing.

Cheers

Well you should get some credit as you sold me one of those 303M transmissions.
Now If I could only find a few more. Do you have any leads ?

 

[rustystud]

Hey plowboy, you out there today?
I was looking at the main housing end gasket in the kit you sent me. This gasket will fit either the 301MG or the 303M transmission. That tells me there was probably a "supplemental" gasket kit made for use on the 303M transmission. So instead of looking for a whole different kit for the 303M we need to look for a supplemental kit to add to the 301MG kit.
Thanks Dave.

 

[rustystud]

OK, here's an update on that front servo mod. Yes this 1953 servo will fit and work just fine in our 303M transmission. So if you want extra braking power going down hills than get yourself this servo.
I found two more in my pile of parts. One I had thrown in the metal recycle bin. Saw it and dug it out today.

 

[M37keppy]

If the gasket company has a minimum order, I’d be happy to chip in for a couple sets for myself. If you need to make the minimum.

 

[m1010plowboy]

Hey plowboy, you out there today?
I was looking at the main housing end gasket in the kit you sent me. This gasket will fit either the 301MG or the 303M transmission. That tells me there was probably a "supplemental" gasket kit made for use on the 303M transmission. So instead of looking for a whole different kit for the 303M we need to look for a supplemental kit to add to the 301MG kit.
Thanks Dave.

Just off the phone with Niagara truck parts. Ralph knows our needs and is looking for a reduction unit seal / gasket kit. He still has parts for the transmissions hiding in a barn that takes some digging to get to......sounds familiar. I am going to PM you a different number and you can text him on the parts we're still missing.

I grabbed a few pics of the sea can casing we have. It's used but sure clean inside. PM coming.

 

[rustystud]

Just off the phone with Niagara truck parts. Ralph knows our needs and is looking for a reduction unit seal / gasket kit. He still has parts for the transmissions hiding in a barn that takes some digging to get to......sounds familiar. I am going to PM you a different number and you can text him on the parts we're still missing.

I grabbed a few pics of the sea can casing we have. It's used but sure clean inside. PM coming.

View attachment 926477View attachment 926478View attachment 926475View attachment 926476

Hey, are you really attached to that main case ? I could use one as one of mine has that nasty crack in it.

 

[rustystud]

Before I start on the rear servo rebuild, I have some really interesting news. As many of you know I collect Military manuals. All types, but especially ones with Automatic transmissions in them. Well I just bought another copy of the "TM 9-8025-2" ( an original June 1957) which makes four copies I now own. It came with a special surprise . It had a 15 page supplemental with it that listed changes made to the HydraMatic in August 1962. One of those was the use of the "overrun" valve in the front servo ! The very same one I was planning to use in my rebuild. How interesting was that !
Seems the military noticed the civilian markets use of it and thought they should use it too.
Only took 5 years. Not bad for the military !

Now onto the rear servo rebuild.

There's really not much to mention except to use caution when removing that monster spring, especially if you do not have the special tool. That means you will need an "Arbor" press or a "Hydraulic" press to safely remove it.


There will be four springs (five in later units) and four metal sealing rings you will need to look at. Also the bores the pistons fit into.
On later models, the second and third spring from the left fit into each other. Our early 303M use just one spring here. This comprises the "compensator" piston spring.


One spring needs to be "pried" off to remove the "accumulator piston" .

On reassembly of servo be very careful to "not" break any sealing rings. Make sure all pistons are at the bottom of their bores and the two main housings (the Body and Accumulator body) go together smoothly. Do not force this housing together ! You can easily break the sealing rings.
One other area needs to be checked and that is the "actuating lever" . For some reason the military decided to have an "open bearing" .
This allows the oil to easily enter the needle bearings, (you can easily see this in the above picture) but it is not needed. All civilian HydraMatics had a solid lever and the needle bearings got lubed just fine.

This "open" bearing causes a weak area on the lever and it can crack here. Normally I would just replace the lever with a civilian one, but the "Automatic" band adjustment is on the lever.

This "lever spring" turns the adjusting nut on the rear band. Works just like an automatic adjusting shoe on a rear brake .
When the rear servo is applied, this lever spring comes into contact with the rear bands adjusting nut and slowly turns the nut.

I've never seen one that totally works correctly. You will never see this adjuster on a civilian unit since you always need to adjust the rear band manually, but it does keep the band somewhat close to proper adjustment. So I'll keep it.
I have debated about installing this "lever spring" on a civilian lever, but it would be such a hassle I haven't done it.

 

[rustystud]

So Thursday I'm going in for a "Spinal Nerve Root Block Injection" . This will lay me up for a day or two. Also, my wife has been after me to finish the Gazebo in the backyard. I need to finish the roof panels. That should take a few days. So, this week and a bit of the next week I won't get into the shop much.
I cannot start the reassembly anyway as I'm waiting on the machine shop to finish my clutch drums and pistons. They were pretty slammed with work.
So don't be alarmed if I don't post for a few days.

 

[Mullaney]

Before I start on the rear servo rebuild, I have some really interesting news. As many of you know I collect Military manuals. All types, but especially ones with Automatic transmissions in them. Well I just bought another copy of the "TM 9-8025-2" ( an original June 1957) which makes four copies I now own. It came with a special surprise . It had a 15 page supplemental with it that listed changes made to the HydraMatic in August 1962. One of those was the use of the "overrun" valve in the front servo ! The very same one I was planning to use in my rebuild. How interesting was that !
Seems the military noticed the civilian markets use of it and thought they should use it too.
Only took 5 years. Not bad for the military !

Now onto the rear servo rebuild.
View attachment 926608
There's really not much to mention except to use caution when removing that monster spring, especially if you do not have the special tool. That means you will need an "Arbor" press or a "Hydraulic" press to safely remove it.
View attachment 926604View attachment 926605

There will be four springs (five in later units) and four metal sealing rings you will need to look at. Also the bores the pistons fit into.
On later models, the second and third spring from the left fit into each other. Our early 303M use just one spring here. This comprises the "compensator" piston spring.
View attachment 926606

One spring needs to be "pried" off to remove the "accumulator piston" .
View attachment 926607
On reassembly of servo be very careful to "not" break any sealing rings. Make sure all pistons are at the bottom of their bores and the two main housings (the Body and Accumulator body) go together smoothly. Do not force this housing together ! You can easily break the sealing rings.
One other area needs to be checked and that is the "actuating lever" . For some reason the military decided to have an "open bearing" .
View attachment 926609View attachment 926610 This allows the oil to easily enter the needle bearings, (you can easily see this in the above picture) but it is not needed. All civilian HydraMatics had a solid lever and the needle bearings got lubed just fine.
View attachment 926611
This "open" bearing causes a weak area on the lever and it can crack here. Normally I would just replace the lever with a civilian one, but the "Automatic" band adjustment is on the lever.
View attachment 926612
This "lever spring" turns the adjusting nut on the rear band. Works just like an automatic adjusting shoe on a rear brake .
When the rear servo is applied, this lever spring comes into contact with the rear bands adjusting nut and slowly turns the nut.
View attachment 926613View attachment 926614
I've never seen one that totally works correctly. You will never see this adjuster on a civilian unit since you always need to adjust the rear band manually, but it does keep the band somewhat close to proper adjustment. So I'll keep it.
I have debated about installing this "lever spring" on a civilian lever, but it would be such a hassle I haven't done it.

.
Wow! That self adjuster is like a mini version of drum brakes on a car.
Really neat way of keeping the band in adjustment...

Oh, and happy doctoring.
Hope they get you fixed up!

 

[1944mb]

On another little modification I'm trying, is replacing the front servo with a 1953 model HydraMatic.
This servo has a really neat little valve built in called the "overrun control valve" .
This valve prevents the front band from slipping when descending grades when the transmission is in 3rd gear thus providing " engine braking" !!!
You ask how is this possible ? This valve allows "mainline" pressure to the front servo "compensator" when normally the compensator pressure is low due to high "Governor" pressure (road speed above 20 MPH) .
Here's a picture of the "normal" front servo.
View attachment 926398
Here's a picture of the front servo with the "special" valve.
View attachment 926397So far I can find no reason it should not work in our 303M transmission.

Does anyone offer a complete assembly on this, where we could get a part number?