Technical 1950 Hydramatic Help

Hey,

I have a few questions about the hydramatic in my 1950 Cadillac.

When Im going up hills, it seems to lug in whatever higher gear its in, 3rd or 4th, and wont downshift, even if its wide open. Ive read I need to adjust the linkage on the carb but Im not sure which direction to move it and how much.

If I accelerate rather quickly from a stop on flat ground it shifts smoothly through the gears. If Im light on the throttle, it seems to wind out 2nd and eventually clunk into 3rd.

I have not checked the fluid. When I replace it, whats the most stock/proper fluid to use?

Thanks everyone for your input.

 

try adjusting the throttle pressure rod tighter (move it forward) a few turns of the nuts. first, be sure you have full throttle with the pedal to the floor.

 

First off, check your fluid level. Use Dextron II or equivalent (this is a general purpose GM trans fluid).
Then take the car for a blast, and report the findings. Does that have a vacuum modulator? If it does, You will see a 2inch round thing shaped like a flying saucer, with a small tube sticking out the top. This connects to your manifold vaccum, and if it is leaking or blocked with crud, this will give all sorts of weird shift problems.

 

Gm considers Dexron VI backward compatable with any gm trans that used any version of Dexron.
From a gm tech bulletin when I worked at the dealership.

 

Thanks for the quick replies guys.

@john walker, when you say forward do you mean towards the bumper or towards the firewall? Im assuming front of the car. How much? Like a quarter inch or more/less?

I just dont want to mess it up terribly. Just being careful. Thank you!

 

I know it's not your main concern, but I don't think you need to worry if you feel a more noticeable "bump" or "klunk" when it shifts into 3rd gear. If I remember correctly, in 3rd and 4th gear the power flow thru a Hydramatic bypasses the fluid coupling and it essentially acts like a lock-up converter on a later model transmission.

 

I read somewhere that 3-4 is always rough, even when brand new. Mine will rapp out 2nd when cold, but it sounds like you need to check the kickdown. Some are vacuum, some use a solenoid, and some use a throttle lever.


Edit: I know this because old mr. Ford put a hydramatic in my 51 lincoln

 

Not true....both of mine have a smooth barely noticeable 3-4 shift. It's the 2-3 shift that's kinda clunky. The only way I can tell it's shifted is by the sound of the motor dropping in rpms.
To adjust the shift points you just change the length of the TV rod. For a later shift you need to make the rod shorter by loosening the rear nut 1-2 turns then tighten the front nut until it's snug. Take it for a spin and repeat as necessary.

 

Shift is controlled strictly by the 'throttle pressure' rod. As was suggested above, adjust the rod (it goes down to the 'passing gear' arm on the side of the transmission, same shaft as the shift link)
Rod has 1/4-28 threads with two locking nuts. Disconnect the fitting at carb lever with the cotter key, depress the throttle wide open. Adjust the transmission pressure rod to its full throttle position, (you can feel spring tension from the transmission lever, go to its end)
Match its fitting pin to the hole by adjusting the length of the rod, and re connect.
Road test, taking note of shift points. If shifts occur too quickly, rod is not 'long enough'. (it 'pushes' to increase pressure) Adjust in 1/16" increments, as the adjustment is sensitive.
Also, when sure trans is shifting normally, take car to 30 MPH and in 4th range ('high gear') step down to wide open throttle, ensuring that it shifts down to 3rd ("passing gear".

Before starting any of these adjustments, inspect engine mounts CLOSELY. (have an assistant stand to the drivers side of car, hood open; hold left foot on brake, gas with right foot. Drive range, 'power brake' slightly; watch for engine 'lifting' on left side; shift to reverse, same test; engine will lift right side.
Broken engine mounts are likely why your adjustment is out of spec.

 

Yes....I stand corrected....this one is the opposite. Make the rod longer.

 

Buy a '50 Cad shop manual. Reprints are not much $$ & will answer every ? you have.

 

I have several hydros from this era. They are purely hydro/mechanical in operation, there is no vacuum involved. Atwater Mike is essentially correct. If the tranny shifts smoothly under hard acceleration the motor mount is a non issue 're' the light throttle acceleration. The 2-3 shift requires both planetarys to change "state" i.e. the front gear set goes from direct to reduction while rear planetary changes from reduction to direct. This is the most complicated action the can occur in the operation of these transmissions. Problems with this shift are the first indicator of normal wear. For a smooth transition the condition of the clutch discs and careful adjustment of the bands is essential. The light throttle cluck during the 2-3 shift is an indicator that normal wear is effecting the clutch/band relationship.This wear is to be expected in a 60+ year old tranny. The clunk is caused by momentary slack (freewheeling) of the gear sets during the shift. A simple adjustment of the bands may be enough to minimize this condition. If you decide to attempt this adjustment, call Rusty at Northwest Transmission and rent the band adjusting gauges, don't arbitrarily adjust them otherwise. This is likely the reason for the condition you described.
The TV valve/linkage is the means to increase line pressure to actuate the servos that alter the state of the planetary gearsets. Since the front planetary needs line pressure to apply it's band and the rear set needs line pressure to release it's band to shift to 3rd gear, low line pressure @ light throttle indicates a TV linkage adjustment is needed.
If you are inclined to make a TV linkage adjustment, which is very simple, be sure to count the turns you make so you can return to the current setting. The 1/4"-28 threads means 1 full turn is a 1/28th of an inch. 2 full turns is 1/14th of an inch, just over a 1/16th of an inch. With these transmissions a 1/16th inch adjustment of the TV linkage can be a significant change in the behavior of these transmissions. Try shortening the linkage 2-4 full turns, if that doesn't improve the light throttle upshift the next step will be return the linkage to where you found it and do a band adjustment. Then again attempt TV linkage adjustment, If that isn't the fix you may need some new soft parts in the tranny.
Because you state your heavy throttle shifts are OK, It sounds like your problem is fixable be adjustments only.
I hope this helps explain what needs to be done.
Best Regards and good luck with all your endeavors, KB.

 

Thanks so much guys. Just about to try the adjustment and check the trans fluid when warmed up after a quick drive.

 

Well. I adjusted it. While testing I ran out of gas, filled it up and now it wont start. Im parked on a slight incline. Tried putting gas in the carb. Idles rough and shuts off

 

Did you crank it over enough to work through any air that might be in the fuel line? If it ran dry, there's probably a stretch of line with air in it that needs to be pumped through. Just a thought.

Also, when you say you adjusted the transmission, what exactly did you do?

 

Ok. Thankfully I just got it home! I loaded it with carb cleaner and it eventually idled long enough to equalize the fuel flow I guess. Earlier the jets werent shooting a thing, even though the glass bowl was full.

What I did was mark the top of the two lock nuts on that trans line off the carb. I then rotated them both two rotations forward.

When I started the car, let it warm up, the idle was a little higher than average. This made it clunk when put into drive.

I went to the bottom of the neighborhood where theres a long incline on the way home to test the downshift. It did downshift right before I ran out of gas. In an effort to restart it at that moment, I set the bar back to the original position. Once I got it running I just drove it home easy, although I tried flooring it once and i lugged with no downshift.

I guess its going to take less than 2 rotations so the idle isnt effected too much.

 

I just, as for the manual instructions, ran it at high idle for about 1.5 minutes, then let it idle normal and check the trans fluid. It looked nice and pink, but seemed over full.

Then it died again. I checked the carb and the jets were shooting nicely. When I rev it, itll kinda miss for a second, then work fine, then idle and die. I have 2 in line fuel filters before the glass bowl to help catch any junk from the tank. The plugs, wires, cap, rotor, coil, condenser, point set is all new. Stumped.

 

I have O/H a bunch of newer ( 70"s and 80's ) transmissions. I would like to tackle my friends hydro . Bottom line, how difficult are they to O/H ? He has a 50 Caddy also.

 

Fuel cap vent blocked or wrong fuel cap?

 

You're right, it is the 2-3, not the 3-4!!!

 

The first thing you need to do is get it to run with out dying. It must be fully up to temperature (when the thermostat opens and hot water flows into the top radiator hose and the choke butterfly is wide open). If it quits as it warms up the curb idle screw needs to be turned in to speed up idle. don't use the screw that adjusts the fast speed idle ramp that connects to the choke. (that's for idle while engine is cold). Now block the wheels, apply E brake, place trans in Drive then adjust idle so it won't stall. Now you are ready to road test the transmission.
I doubt that a minute and a half is sufficient time to allow engine or trans to be fully warmed up.
It is unlikely that adjustment to shorten the TV linkage from the carburetor bellcrank to the trans throttle valve would cause a faster idle but would actually lower idle speed because the return spring inside the tranny's valve body will work to close the throttle. I assume that the linkage adjustment you are attempting is from under the car at the trunnion affixed to the throttle valve (TV) lever. Adjustments elsewhere in the linkage may well effect the carburetor opening and idle speed. If Cadillac did not put the trunnion at the TV lever but at the bellcrank off the carb, you shouldn't move the nuts towards the front of the car but rearward. remember, to increase TV line pressure the lever must move further forward. To do that the linkage must be shortened no matter where the adjustment is. Now shorten the TV linkage until you get a kick down shift to a lower gear when you floor the throttle. Then you should have smooth shifts up through the gears upon light throttle acceleration.
The clunks don't necessarily have to be from the tranny, there is a spline yoke to the driveshaft that is most likely quite worn as is the lash between in the ring and pinion in the differential. A U joint could be losing its needle bearings, any one of those would cause a clunk and are more likely than a major issue in the tranny.
Best regards and good luck with all your endeavors, KB.

 

What cars would have had these trans? Caddy Olds Buick? I think there were other makes that used them too. Was wondering about one behind a 261 gm six cyl
don

 

They were also used in Lincoln's and tanks. I doubt they would work very well behind a 6 cylinder. They aren't very efficient and take a lot of power to operate.....not to mention very heavy. A power glide would be a better choice.

 

Thanks. I suppose I was actually lengthening the bar? I was in fact moving the nuts where it connects to the carburetor, not where it connects to the trans under the car. Ive learned with this car if the idle is too high, it will clunk when put in reverse or drive. If I have the idle nice and low then that doesnt happen.

 

Actually, these transmissions were factory optional on 1953 and later Chevy and GMC pickups and heavier trucks. The same trans was used with a shiftable 2:1 gear reduction in busses and dump trucks as well as Korean war era military Deuce and a Half's. The Chevy pickups had 235 sixes while the GMCs used a 248 inline six. I suspect that the dump trucks had the 261s in them. My own 54 Jimmy half-ton has a military 302 hooked to it's stock Hydro.
To TXTurbo, your comments regarding efficiency and power consuming are completely wrong. These require only the power to drive the front pump that generates the fluid pressure to apply the clutches and bands just like every other automatic transmission. In fact because the rear planetary's band is clamped by a spring it doesn't even need pressure to engage. To further re-enforce my argument, the original Hydromatics did not have that inefficient torque-converter that create most of the heat and require a auxiliary cooler as do modern automatics. The original GM Hydromatic used a fluid-coupler not a torque-converter. These fluid-couplers become nearly as solid a connection as concrete at about 750 RPM. That is why the idle must be set below that RPM to avoid lurching when shifting into gear or coasting to a stop.
If you can reflect back to the golden days of gasser drag racers, remember the Stones Wood Cook Willys car and others with their front wheels 4 feet in the air. Those where GM hydro trannys, basically stock units with a B&M manual throttle body mod in them. Those gassers spun-up their motors at the line in neutral and threw them into gear when the light went green, The inertia in the fluid coupler with about 2 gallons of trans fluid in it was what lifted those front ends so high in the air. These transmissions are extremely tough and efficient.
See my truck on my profile page.
Best Regards to all and good luck with all your endeavors, KB.

 

As well as Nash, Hudson. Kaiser-Frazer and Rolls Royce.
Best Regards and good luck with all your endeavors, KB.

 

Good write-up and accurate except for one thing that I have to disagree with.

The Gassers using Hydros did not rev them up in neutral then throw them in gear when the light went green. The vanes in the fluid couplings would be cut to allow more 'slip' and a higher stall speed. Additionally the vanes would be brazed to the torus for strength. I was around several strip-only gassers in the early '60s and had a hydro behind my 348 Chevy and NEVER saw anybody (including Stone, Woods and Cook) wind one up in neutral then throw it in gear.

One more thing, the Gasser units were not stock with just a modified throttle body - clutch packs were modified, line pressure and pumps beefed-up and governors were modified among other things

 

Might be hard to read -

 

There's a lot of knowledge and reference material on Hydro's here: http://www.jalopyjournal.com/forum/social-forums/hydro-tech.671/

 

Dave, thanks so much for your comments and corrections. Back in the 70s when I hooked a 4 sp series 210-U Hydro behind a Chev 261 that's how I ran mine when doing light to light street drags. I would rev the motor to maybe 2500 and drop it in gear, then immediately pull it to the 1-2 position to keep it in second way past its normal shift point, then manually move to 1-3 if the next light was that far away. With cheater slicks it would almost pickup the front end on starts. I always thought that's how the Gassers did it. I finally blew the front pump.Now that I'm in my late adolescents, i.e. 69, I would never do such things to my Jimmy's tranny now, or participate in street light drags, well maybe not. I have several spare Hydros as well as different sizes of fluid-couplers and torus wheels from cars, trucks and deuce&1/2s. There are gearsets that have different ratios and 4 planetary gears as well as clutch packs that can hold from 5 to 9 fibers. I have recently acquired a genuine B&M hooked to a 394 Olds but have yet to tear it down to see what mods it contains. I knew about brazing the torus wheels as they do to modern torque converters and have seen comments against milling of the vanes for reasons I don't recall, but that would certainly increase the lockup RPM. In any case there are many possibilities for modification using available stock parts even today.
I especially appreciate you're posting the article on Hydro mods, I'll read it with great interest and try to absorb it's info. I've found a few articles about B&M over the years and apparently they had varying degrees of mods that could be done to the Hydro but the typical unit Joe average would attain was a simple valve body mod. The article you have posted mentions "Cal Hydro", were they a precursor to B&M? Where can the original article be found?
That's enough, We shouldn't hijack this post, after all we are trying to get a 50 Caddy to shift correctly!
Best Regards and good luck with all your endeavors,KB.