1949 Hydra-Matic transmission

[49 Caddy]

  Anyone re-built one of these?  I bought the car with the engine seized up, so I don't know the condition of the tranny.  As everyone knows, this is easier to install connected to the motor in (1) piece.  I have rebuilt the motor and do not want to have to pull it back out from transmission issues.  I can't decide to attempt to rebuild it myself or to just take things apart, clean, & just replace gaskets & seals.  Can't find a shop to take it to for rebuild.  Rebuild kits do not look to have too many parts.  Suggestions/Advice appreciated. 

[Macabry]

I'm in a similar position for a '52 ... I know she'll shift but I need to give her a service and seals/gasket charge ... I've just put up a thread looking for service books etc.

... fingers crossed

[49 Caddy]

  I just ordered a 1961 edition of a Service Manual for 1949-1961 Hydra-Matic Transmissions.  Supposed to be easy enough for someone with no previous experience rebuilding this tranny.  We'll see!

[Jay Friedman]

  I just ordered a 1961 edition of a Service Manual for 1949-1961 Hydra-Matic Transmissions.  Supposed to be easy enough for someone with no previous experience rebuilding this tranny.  We'll see!

Hydramatics are complicated.  If you do take it apart and then put it back together, it pays to be very organized.  Take photos of every component before you dismantle it.  Keep parts from each component together and take careful note of the position of the many spacers and bushings.  Some resemble others and can easily be re-installed in the wrong place. 

[PHIL WHYTE CLC 14192]

I rebuilt mine in my 54 CDV. I read the shop manual over and over for around six months prior to doing it. I printed and laminated the illustrations from the manual and the parts book. The main transmission parts store here in the UK put me in touch with a guy who had worked on these transmissions for years, Len Stoller (RIP). He kindly invited me to rebuild it in his workshop and if I hadn't I would have messed it up. For instance he took a file to some of the aftermarket parts and most importantly he set up the clutch drums with plain spacer plates he had had made in different thicknesses. This has given it extremely smooth shifts.

[Macabry]

It's that knowledge that's becoming harder to find as the earlier technology "ages out" ... there are some useful videos on youtube, but no full build 👍

[49 Caddy]

  Thanks.  Looking more like I just might want to take covers off and have a good look before deciding what to do.  As mentioned, I don't know if there were issues or not, I just know it sat in a barn for over 40 yrs. and the engine was seized.

[PHIL WHYTE CLC 14192]

The manual shows you how to apply compressed air to test the transmission. Probably worth at least doing an external seal replacement.

[wheikkila]

I have worked on transmissions for years. If that transmission has sat for forty years forget about it working. The seals are as hard as rocks. The parts are stuck together and will be hard to get apart. I just finished rebuilding a 54 Packard transmission that sat for forty some year. I had to pound some of the planetary gears apart. And most of the bushings were bad from no fluid passing through them for years. Take all the photos you can, read everything and watch every video you can. Good luck and let us know what you do.
Thanks Wayne     

[Rossoroo]

Here's a link to Part 1 of 5 parts on YouTube.
This guy appears to be a Guru of transmissions.
He does the Hydramatic on these videos

https://www.youtube.com/watch?v=ygkRuwCpKxU&list=PLpiikgzFQkaaLRsU0O59MoNClP7AQk_yl&index=15&t=53s

[Caddy Wizard]

I am an excellent, experienced mechanic and can do most anything on a car.  I have, however, been vexed by the Hydra-Matic transmissions.  I find them extremely reliable, but difficult to rebuild.  I have had to resort to having a specialist rebuild them for me. But  I am very interested in overcoming this mental roadblock and learning how to do them myself.

I say that as background for the following advice:  If you have reason to believe that the unit is/was reasonably functional, you might try replacing the gaskets and seals while it is out.  That can be done by anyone with good mechanical skills if they are careful.  Good parts are available from FATSCO to do this work.  The rear (tail shaft) seal is a pain to remove -- I end up chiseling them carefully to release them from the tail shaft housing.  The front seal can be removed from the unit with a screw and a slide hammer.  The gaskets for the pan are a straightforward matter, just be sure to flatten the bolt hole bosses if not flat (as from over-tightening).  Be sure to tighten the pan bolts to the proper (low) torque -- you might need to borrow a buddy's inch-pound torque wrench.  The side pan also has one or two seals on the shaft sticking through the pan -- again, this is available from FATSCO.  Use a drain plug seal that has a metal outer part with a rubber inner part -- like this one: https://www.amazon.com/Dorman-65274-Metal-Rubber-Gasket/dp/B00062YSF0/ref=asc_df_B00062YSF0/?tag=hyprod-20&linkCode=df0&hvadid=241973068692&hvpos=&hvnetw=g&hvrand=15558503035451703553&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=9010953&hvtargid=pla-570818043250&psc=1 (not sure that this is the correct part number, but this is the style that I find seals the best against leaks at the plug).

With a bit of care and some time, you can make the transmission drip-free.  Don't be afraid to try this.

[Omarine]

Hi Phil, your comment about the clutch spacer plates for smooth shifts is very interesting to me. I had a 54 trans rebuilt for to replace the 1950 trans that was in my '52 CDV.  the 2-3 shift improved, but i still think it could be better based on another car i rode in once. 

cheers
oscar

[Caddy Wizard]

Hi Phil, your comment about the clutch spacer plates for smooth shifts is very interesting to me. I had a 54 trans rebuilt for to replace the 1950 trans that was in my '52 CDV.  the 2-3 shift improved, but i still think it could be better based on another car i rode in once. 


cheers
oscar

The 54 transmissions were the smoothest up to that point.  Rather refined.

[Joe Jensen]

I rebuilt my Hydra-matic myself.  I made plenty of mistakes (most corrected prior to installation.).  There are some specialty tools required to do the job.  Another member loaned me the tools to do the job.  It is much easier to rebuild with the correct snap ring pliers, you need a special tool to install the drums on the shaft and the internal band adjustment tools are much better then the external ones.

Just take your time, take a lot of pictures.  There is a good Hydra-matic manual the Pontiac released for these years (that was my go to resouce because the shop manual isn't detailed).

Note:  the Hydra-matic was the first transmission I ever rebuilt myself.  It is complicated, the proceedures must be followed and it has many more parts then an engine.


Good luck!
Joe

[PHIL WHYTE CLC 14192]

Oscar, I so wish that I had written down what clearance he worked to with the spacer plate, he packed each clutch drum and checked them with a feeler gauge and swapped the spacer plate until it was correct. The plates were just the standard plain clutch plates in different thicknesses. I believe this method is used by rebuilders on the later hydramatics, maybe someone with experience on these can enlighten us? Also for smooth shifts micro adjustments of the TV rod can smooth it all out. Phil

[PHIL WHYTE CLC 14192]

On the subject of the special tools (Kent Moore) I know have them. But when I rebuilt my transmission with Len Stollar he adjusted the bands by applying compressed air to activate them and set them up while applied. After this I managed to get two sets of the internal band adjusting tools, a set for me and a set for him.

[Caddy Wizard]

Oscar, I so wish that I had written down what clearance he worked to with the spacer plate, he packed each clutch drum and checked them with a feeler gauge and swapped the spacer plate until it was correct. The plates were just the standard plain clutch plates in different thicknesses. I believe this method is used by rebuilders on the later hydramatics, maybe someone with experience on these can enlighten us? Also for smooth shifts micro adjustments of the TV rod can smooth it all out. Phil

The band adjustments and TV rod adjustment will smooth out most of the shifts.  You can usually get the 1-2 and 3-4 shifts to be quite smooth.  But the 2-3 shift is another animal altogether.  It is tricky, because as the professor said in the video listed below, in order to avoid the "flare" or "bang" in this shift, all four control changes need to happen in close coordination.  That is, one band needs to release, one clutch pack needs to release, one band needs to engage (lock) and one clutch pack needs to engage -- all at the same time.  If one happens early or late, the result is a shift that is harsh or sloppy.  I have had 20 old Cadillacs and some had decent 2-3 shifts, while others were harsh, while still others were sloppy, independent of how well the 1-2 and 3-4 shifts were.

It almost seems like luck if your car has a really good 2-3 shift.  But maybe i am wrong...

[Bob Schuman]

I have been around long enough to have ridden in and driven a variety of Cadillacs, Oldsmobiles, and Pontiacs having the old (1940-1955 design) Hydra-Matics, and have some observations that may be pertinent.
The first HM car I drove was a 51 Cadillac 62 sedan in 1953, and I immediately noticed the shifts were much smoother than in Olds and Pontiac cars. I assumed that quality control for Cadillac units was superior to the "lesser" brands. My Dad bought a new 1955 Olds Super 88 sedan that always had a very rough 2-3 shift, almost like two very rapid jolts. I took the new car back to the dealer where the mechanic (not called technicians in those days) adjusted the throttle pressure linkage with no improvement. I do not recall the bands ever being adjusted, and it always had a rough 2-3 shift during eight years of ownership.
The next HM equipped car I have had is my present 1951 Cadillac 6137 coupe, with 90,000 miles. It's 2-3 shift is as bad as the 55 Olds, despite my repeated adjustments and intentional misadjustments of the bands and linkage. I can misadjust until the engine flares during shifts, without smoothing the 2-3 shift. This transmission may have been rebuilt sometime earlier in its life, that I do not know.
During ownership of the 51, I bought a 49 Cadillac having a 1953 HM transmission that was rebuilt by former CLC member Jack Hoffman, who knew HM transmissions well. It was definitely the nicest shifting HM I have ever experienced. During my ownership I often felt that GM would have had no need to develop the 1956-65 Controlled Coupling Hydramatic if all of the old design shifted like the one in my 49.
The bottom line of all of the above drivel is that I think that quality control issues with the 1940-1955 design cause some transmissions to have a much better 2-3 shift than others, despite any adjustments you can make on the bands and linkage.
As a separate issue, I have read comments by various writers that Buick could not use the HM transmission because its rough shifting was unacceptable in the Buick with its torque tube drive. Nash, with its torque tube drive, used GM Hydramatics for years, with no complaints that I am aware of. Hmmm!

[wheikkila]

When you rebuild a transmission all the clutch drums have a clearance spec. How you achieve this is by changing the clutch plates or the pressure plates. Sometimes you have to change both. I just finished working on a Ford c4 for a club member and the drums were packed to o clearance. They should be 30 to 50 thousands roughly. I had to purchase special plates to get my clearances correct. It's not hard, it just takes time on the front end. Good luck with your transmission.
Thanks Wayne