1956 Hydra-matic/Jetaway transmission mystery ????

[Jose Gomez]

Well finally warmer weather allowing me to get back to my projects..!

I just finished the rebuilt on my spare Hydra-matic/Jetaway with a fresh rebuild kit, the “works”. It took me a bit longer than I expected as I had to reverse-engineered a few of the tools to get things going, such as the J-6121, J-6129, J-6135, and J-6282. Last item was dismantling the control valve assembly for cleaning and inspection before closing this puppy.  The spare transmission has serial number C56-116441 versus the one on the car which has C56-105050.

Once all valves were removed and individually dismantle and valves, springs, etc were place in sequential order, I’ve notice a few discrepancies (physically versus the shop manuals pictures) from the following valves;

The coupling valve body had a large spring behind the overrun clutch valve; the shop manual shows no spring just the valve. 
The shift valve body had no neutral clutch valve or spring this large cavity was empty; the shop manual shows a large spring and a valve. 

Looking at other documentation for the Hydra-matic/Jetaway 1958-1964 these valves had a few some minor changes through the years, and per my research even these manuals have the same differences that I’ve notice within a respective year.

So far what I’ve found the closer model for the coupling valve body with the large spring seems to be for the 1958. So it seems the 1956 and 1957 have no spring, ok. My coupling valve body has stencil 861 7667, and can’t find this in the Cadillac MPB. Mystery one? 

As for the shift valve body I’ve found a 1956 Motor’s Auto Repair manual showing the shift valve without the large spring and neutral clutch valve. So it seems they may have multiple variances in the 1956, ok. My shift valve body has stencil 861 7597 (back) and 861 6367 (front), and can’t find these in the Cadillac MPB. Mystery two? 

I know these could possible belong to other GM brands that used Hydra-matic/Jetaway transmission Pontiac or Olds since they share the same tranny. Also, I would assume these valves could be interchangeable between several years, maybe forward and not backwards compatible.  Mystery three? 

Sorry for the long winded thread, this one got me thinking..! Any input or comments??

[Jose Gomez]

The last picture attached for the 1956 shift valve w/out the neutral clutch valve.

[Jose Gomez]

Well finally warmer weather allowing me to get back to my projects..!

I just finished the rebuilt on my spare Hydra-matic/Jetaway with a fresh rebuild kit, the “works”. It took me a bit longer than I expected as I had to reverse-engineered a few of the tools to get things going, such as the J-6121, J-6129, J-6135, and J-6282. Last item was dismantling the control valve assembly for cleaning and inspection before closing this puppy.  The spare transmission has serial number C56-116441 versus the one on the car which has C56-105050.

Once all valves were removed and individually dismantle and valves, springs, etc were place in sequential order, I’ve notice a few discrepancies (physically versus the shop manuals pictures) from the following valves;

The coupling valve body had a large spring behind the overrun clutch valve; the shop manual shows no spring just the valve. 
The shift valve body had no neutral clutch valve or spring this large cavity was empty; the shop manual shows a large spring and a valve. 

Looking at other documentation for the Hydra-matic/Jetaway 1958-1964 these valves had a few some minor changes through the years, and per my research even these manuals have the same differences that I’ve notice within a respective year.

So far what I’ve found the closer model for the coupling valve body with the large spring seems to be for the 1958. So it seems the 1956 and 1957 have no spring, ok. My coupling valve body has stencil 861 7667, and can’t find this in the Cadillac MPB. Mystery one? 

As for the shift valve body I’ve found a 1956 Motor’s Auto Repair manual showing the shift valve without the large spring and neutral clutch valve. So it seems they may have multiple variances in the 1956, ok. My shift valve body has stencil 861 7597 (back) and 861 6367 (front), and can’t find these in the Cadillac MPB. Mystery two? 

I know these could possible belong to other GM brands that used Hydra-matic/Jetaway transmission Pontiac or Olds since they share the same tranny. Also, I would assume these valves could be interchangeable between several years, maybe forward and not backwards compatible.  Mystery three? 

Sorry for the long winded thread, this one got me thinking..! Any input or comments??

Folks,

WOW ..111 hits and no reply this one was a tough one.!

Latest updates..!

First able thanks to Lou Commisso for providing a snap shoot of Cadillac Serviceman December 1955 which explains the missing clutch valve mystery. This particular valve was removed once GM (Cadillac) changed the driving clutch plate from hard composition to the cork type; it also noted Fig 12-94 on the manual changes should be made to reflect the removal of the clutch valve.

Second it seems the number stenciled on these valves may not correlate to the complete valve assembly listed in the manuals, it could well be just the part # for the plate without the springs, valves, etc. Not confirmed just my speculation. My second tranny C56-105050 has a different coupling valve # 861 6365 with no overrun spring which there is also there is no listing on the manual.

[Johnbezik#15976]

Why don't you contact "Fatsco" in New Jersey they specialize in the old stuff and probably can answer most of your questions.They can also help you with the bolts you are looking for they do sell hard parts too.

[Jose Gomez]

Why don't you contact "Fatsco" in New Jersey they specialize in the old stuff and probably can answer most of your questions.They can also help you with the bolts you are looking for they do sell hard parts too.

John,

I call Fatsco today and they have them at $3.00 each, I did inquired if they were gold plated..! 

I was thinking of replacing all (12 for each tranny) but at these prices I have to be conservative.

Thanks for the feedback..!

[The Tassie Devil(le)]

At $3.00 each, they would be a steal.

Making them at a Machine Shop you would be looking at $10.00 each.   At least half a dozen processes to go through to make each one.

Bruce.