Videos & Photos of rebuilding transmission

[stephenfeldmeier]

No problem we can do this any way you want, I never thought of doing this with other person is following along, good idea, I like that. When I rebuild one the first thing I do is to call Memphis Equipment go to the parts department and get a hold of John, tell him that you are doing a rebuild and you need all the gaskets and seals he has for the transmission and reduction gear box. Depending of how much wear there is, all the gaskets and seal comes as a kit, for instance you have a leak in your oil cooler area, they have a rebuild kit just for the lower pan assembly. Now they do have most of the seals such as some copper thrust seals but those aren't usually bad, and you'll have to order those separately, So just start out getting the gasket and seal kit for both transmission and reduction gear box section, you as well as I will see if we need anything else along the way. In your order if you don't have one get a parts catalog for the GMC "M" Series, that really comes in handy.

What I'm doing now is putting my transmission together without any gaskets or such, plus I’m only finger tightening the parts together. This way I can go over the disassembly and what to look for, plus with the extra components I can disassemble those and show the insides of them.

I will take a picture of the gasket kit when it arrives, as it varies from time to time do the availability of parts.

 

[stephenfeldmeier]

transmission

Well a little TLC, it does look too bad for sitting in boxes 9 years, waiting for the parts from Memphis Equipment. this is what the transmission looks like when you remove the drain pan, access cover to the valve body, and reduction gear housing.

I'm still getting all my notes in order and setting up the garage for photos and videos.

 

[stephenfeldmeier]

The transmission is upside down.

 

[stephenfeldmeier]

The reduction gear section

 

[stephenfeldmeier]

Cutaway views of transmission

What I’m going to talk about next is just the basic shift pattern, I’m not going into detail about throttle settings, control valve setting or reduction gear operation HI / LOW. This is only going to cover the transmission from 1st to 4th.

The Players

Flywheel / Torus Cover & Shaft
Drive Torus & Shaft
Driven Torus & Shaft
Front Planetary Unit
Rear Planetary Unit.

The Planetary Units are made of a drum and multi disc clutch assembly in side. A band encircles each Unit. Each band has its own servo. Each multi-disc is activated by its own piston. When the band tightens around the drum by the servo, the Unit is in REDUCTION, when the bands are released and the clutch piston is activated, the Unit is DIRECT DRIVE.
When neither the drum band or clutch is activated, the Unit is in Neutral.

Note: if the band is tighten around the drum at the same time the clutch is activated, this will lock the Planetary Unit, not an operational feature of this transmission. Just for your FYI.

The basic design of just the transmission is set up in the following sequence: (equivalent of the children’s song “knee bone connected to the hip bone, hip bone connected to the back bone”)

The Flywheel & Torus Cover is connected to the Front Planetary Unit, the out put of the Front Planetary Unit either being reduction or direct drive is connected to the Main Shaft.

The Main Shaft is connected to the Drive Torus and is also the input for the Rear Planetary Unit. As the Drive Torus is driving the Driven Torus through fluid coupling at the same RPM, The Rear Planetary Unit output is connected to end of the Driven Torus shaft, which is connect to the output shaft. This sequence never changes, what changes is the output of the each Planetary Unit.

 

[stephenfeldmeier]

Note, automatic transmissions do not change gears as manual transmissions; all the planetary gears are always connected to the same components and are never disconnected. The operation that is happening in the transmission are: bands tightens or releasing, OR the clutch pistons are activated or released.
In words, here is the sequence of reductions; but for ease of understanding, I will refer to it as gear selection.

1st gear-- Front Unit BAND ON (reduction) -- Rear Unit BAND ON (reduction)
2nd gear -- Front Unit CLUTCH ON (direct drive) -- Rear Unit BAND ON (reduction)
3rd gear -- Front Unit BAND ON (reduction) -- Rear Unit CLUTCH ON (direct drive)
4th gear -- Front Unit CLUTCH ON (direct drive) -- Rear Unit CLUTCH ON (Direct drive)
In the cutaway you will notice different colors, these colors will not change the meaning.

GREEN --------------- Engine RPM
ORANGE –---------- 1st set of reduction
Any Striped Color – DRIVEN TORUS output, the same color as the DRIVE TORUS
BLUE ------------------2nd Stage of reduction.

The cutaway drawings will make this clearer.

1st Gear Drawing.

As you can see the flywheel and torus cover is connected to the Front Planetary Unit. We have already said the Front Unit Band is TIGHTEN, so, the first stage of reduction is through the planetary gears (where GREEN meets Orange). (Approx 1.55 to 1 ratio here)
The output is the Main Shaft (solid ORANGE), as we can see it’s connected to the Drive Torus and also connected to the Rear Planetary Unit (input side).
The next operation is the Hydraulic Coupling; this is where the Drive Torus is driving the Driven Torus at the same rpm. The Driven Torus shaft is connected to the output side of the Rear Planetary Unit were it’s connected to the Output Shaft since we already know the Band is TIGHT on the Rear Unit. The second set of reduction is from the Driven Torus Shaft to the Output Shaft. (Approx. 2.63 to 1 ratio here) so total reduction ratio is 4.08 to 1

 

[stephenfeldmeier]

2nd Gear Drawing.

As we can see the First Planetary Clutch is in Direct Drive, The whole unit is turning as one. Which means if you follow the color GREEN, the Main Shaft, both Torus Halves and the Driven Torus Shaft are all spinning at engine RPM.
We already know by now the Rear Unit Band is TIGHT (reduction) so our only reduction in this case is 2.63 to 1.

 

[stephenfeldmeier]

3rd Gear Drawing.

We know in this gear the Front Planetary Unit Band is TIGHT (reduction) and the rear Planetary Unit Clutch is ON (Direct Drive). The only reduction in this case is from the Front Planetary Unit.

Now when we go from 2nd to 3rd, we asissit the torus halves and the transmission goes into direct drive by assisiting the torus halves.

When we select 3rd we relase the band on the rear drum and activate the rear clutch pistions, this squeezes the main shaft clutch plates which turn the drum and it's ring gear. Since the ring gear is turning 1.55 to 1 the planetary gears (connected to the output shaft) driven by driven torus shaft sun gear turns the output shaft to the same ratio. Due to the pressure on the driven torus shaft sun gear from the drive torus, it acts like a rotating locked sun gear.

When this happens, the planetary gears can't turn because the drum is locked to the main shaft. At the same time and the drive torus is supplying constant pressure to the driven torus and the driven torus shaft sun gear locking it from turning in the opposite direction, which in this case would be required for the planetary gears to rotate. This shows the main shaft and the drum and ring gear are supplying the majority of the force to turn the output shaft.

The jolt you feel is the rear planetary unit clutch piston activating and driving the planetary gears of the output shaft assisted by the driven torus sun gear going from a ratio of 2.63 to 1 ratio to a 1.55 to 1 ratio assisted by the engine.

 

[stephenfeldmeier]

4th Gear Drawing.


The easiest to understand, since the Front and Rear Planetary Units are in (direct Drive)
Everything is spinning at engine RPMs (no reduction) 1 to 1 ratio

 

[M-37Bruce]

Size Does Matter

Hey Steve,
What a great thing to do for all the M-211/M-135 crowd, makes me wish I had one also!
As big as it looks on your bench, I'm guessing it took more than yourself to get it there?
Seasons Greetings,

 

[stephenfeldmeier]

correction

In the photo if the transmission drive-line, I mentioned that there were 6 clutch plates in the rear Planetary Gear unit, Well again my typing skills come through again.

In the front planetary unit there are 5 floating clutch plates with 4 stators

In the rear Planetary Unit there are 9 floating clutch plates with 8 stators

Sorry if I confused anyone.
Steve

 

[hippiedude]

steve you are doing a awsome job..... you make it real easy to follow .....Thanks......

 

[stephenfeldmeier]

You know I forgot to show you guys reverse. I’ll add a picture later because I have to play choo-choo but, when you select reverse here is what happens;
As you see in Reverse, everything the same for 1st gear except the Rear Planetary unit is in Neutral - Band off and Clutch Off. The Rear Planetary unit has to be in neutral because as previously discussed when the Reverse Forcing Cone forces the Reverse Gear against and the Stationary Cone making the Reverse Gear a stationary ring Gear, (Yellow in this picture) this forces the Output Shaft rotate in a different direction, (remember we talked about that earlier) since the Rear Planetary Unit is geared the Output Shaft by planetary gears, the Output Shaft is forced to turn in the opposite direction and the Rear Planetary Unit has to spin in the opposite direction also, the only way this can happen is the Rear Planetary Unit is in neutral. The reason the Driven Torus Shaft can rotate Output Shaft in Reverse direction is because the end of the Driven Torus Shaft is the Sun Gear, which is Surrounded by the planetary Gears, which is surrounded by a Ring Gear (Bolted to the Rear Planetary Drum), This also adds one more stage of reduction then from first gear at this point bring the total reduction to 4.54 to 1.

 

[badgmc56]

Thanks Steve for all you are doing. I was going to rebuild my old tranny but didn't want to pull it out again if there was a problem. Wish this thread was going on before I bought a rebuilt unit. Not knowing what to look for was my biggest concern but now you are taking care of that. Thanks again.

 

[stephenfeldmeier]

Thanks Steve for all you are doing. I was going to rebuild my old tranny but didn't want to pull it out again if there was a problem. Wish this thread was going on before I bought a rebuilt unit. Not knowing what to look for was my biggest concern but now you are taking care of that. Thanks again.

You’re Welcome,

When I got my M211s, 1 good truck, 3 only good for parts, I knew absolutely nothing about a M211, I didn’t even know how to start it, much less drive it. I got my learning experience through the Fire Department. (All Trial and Error). Working on the fire department truck along with mine, I made every mistake that was humanely possible. I was fortunate enough to have three trucks standing by, so if I did break something, I had a spare. I was even stupid enough to drive my truck on a 20 mile round trip with no engine gauges hooked up. of course with Murphy's Law the oil pump regulator came out of the oil pump and seized up the engine. If I had the gauges hooked up, I would of seen the oil pressure gauge reading ZERO.

So when it came time to fix my transmission (had no reverse), I bought every m211 related maintenance manual I could find, believe me, there were times when I doubted myself and wondered why did I ever take on such a project. (I just wished someone did this when I was doing my truck)

So, I just went step by step, learning as I went. Now, rebuilding these transmissions is no more difficult for me then changing sparkplugs. One of the easiest and simplest components on the truck to work on.

My goal is to take the fear out of every M211 – M135 type truck owner, of dropping the transmission, going into it to fix a problem. If you have to go inside the transmission to fix it, 99% of the problem is going to be a simple removal and replacement of a part.

So what I’m doing now is showing the “basic operations”. Once you have the basics down, then we’ll go into each and every component of the transmission and learn its function. I’ll do this through power point. So when its time to rebuild it, I’ll be able to say well the first part that goes into the transmission case is the Oil Delivery Sleeve. Then every body will know that the Oil Delivery Sleeve routes oil pressure from the control valve ports to the front and rear planetary unit’s pistons, plus also its the main shaft bearing.
In the end, you should feel able enough to put it together blind folded.

 

[stephenfeldmeier]

reduction

Reduction Operation
Again we are working with a Planetary Gear Unit. The reduction gear section Planetary Gear Unit is more massive in construction than in the transmission side also instead of using a band to hold the drum for reduction, the reduction section uses a Forcing Piston (Yellow) and a stationary Cone (Green) and the Reduction Driven Cone (Pink the same function as the band).

Again for reduction in a Planetary Gear Unit we need to hold the drum so in this case we activate the Forcing Cone Piston (Yellow), which forces the Reduction Driven Cone (Pink, same function as the band) against the Stationary Cone (Green).
This holds the drum allowing the Output Shaft (Orange) to turn its sun gear in the Planetary Gear of the Reduction Unit Shaft (Blue), this give a reduction of a 3 to 1 rotation ratio.

 

[stephenfeldmeier]

reduction section

In HIGH RANGE the pistons activate and lock the Planetary Gear Unit as one with the planetary Gears of the Reduction Shaft. Everything is turning at the same rate as the transmission Output Shaft

 

[stephenfeldmeier]

Planetary Gears

Now since we have covered the basics on the basic operation, I feel I did not cover the planetary Gear Units very well, so we will look a typical Planetary Gear Unit. Even though the basic shape will very slightly, the operation will stay same.


Remember Band Tight – Reduction
Clutch On - Direct Drive.


Here is how it’s works;

Let’s look at the Input Shaft (Blue) with the band (Red) ON. Band ON prevents the yellow drum from moving. So the only two components then are free to turn are the Input Shaft and the Output shaft. AS you can see the Output Shaft Will turn at a reduced speed, in the M303M Transmission the Output shaft is also the Input for the Rear Planetary Gear Unit.


Let go to Clutch ON the (Yellow Pistons) the pistons squeeze the Clutch Plates (Green) that are attached to the Output Shaft Gear and the Stators (Yellow) that are attached to the drum (Yellow) Since the yellow and green are locked up the only thing can turn is the whole assembly is the assembly it’s self (1to1 ratio)

I hope this clears things up

 

[stephenfeldmeier]

transmission seals

Well here is all the basic seals you will need to rebuild a transmission. Memphis Equipment will build this kit for you if you tell them its for a complete rebuild. All of these seals and gaskets for $135.00, not a bad price.

 

[M215]

GMC Hydromatic

Hello Steve,
I have just had a chance to read your thread about the tranny rebuild project, all I can say is THANK YOU!!!!

I have a spare Hydromatic for our GMC that I would like to rebuild, your info will be very helpful.

Was Memphis able to supply all the needed parts for the rebuild? I thought some of the rebuild parts were no long available. I had to reorder the large gasket for the belly pan 4-5 times because they were so brittle from age they would disintegrate during shipping.

I installed a carriage bolt in the shift towers slot to prevent accidental shifting into hi-range reverse.

Karl