Rob1960

"Automatic Clutch" ??? in a 1934 dodge

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Anybody ever heard of an "Automatic Clutch" in a 1934 Dodge. A Dodge advertisement for that year describes shifting without using the clutch. The ad describes "the vacuum from your engine is used to open or close the clutch-valve. It's all entirely automatic." How many years did dodge offer this feature? How reliable was it? [color:"red"] <img src="http://www.aaca.org/ubbthreads/images/graemlins/wink.gif" alt="" />

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Rob,

I believe it was available from '32 to '34. Apparantly it was not such a great thing. Perhaps when it was new bit later when the engine had some wear and the vaccuum was not as great it did not work correctly. It had a pendulum valve assembly that sensed when the car was not moving and a oiverriding linkage that hooked to the accelerator. There was a large vaccuum cylinder not unlike a power brake unit fastened to the clutch linkage. When the car was 'at rest; the clutch was held in. In order to move forward one pressed the accelerator and that overriding linkage coupled with a momentary loss of vaccuum caused the clutch to release and engage. Obviously all things associated with the engine had to be in top operating condition in order for it to work properly. I have a technical adjustment data sheet and the first thing it says is to make sure the engine is operating at optimum performance before attempting any adjustment. I hope this helps.

Rodger "Dodger" Hartley

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Dodger -

Thanks very much for your reply and great information. Was there some sort of switch to turn the AUTOMATIC CLUTCH on or off? In OFF mode, I assume the clutch and gearshift were operated just like any other standard shift car? In the ON mode, [ if everything was working properly] am I correct that the driver did not use the clutch at all, and simply moved the gear shift to Low and then stepped on the gas? When it was time to upshift or down shift, did the driver simply let up on the gas pedal, and then do the shift? If it worked in this manner, am I correct that when going down a hill, and the driver let up on the accelerator, was the car actually drifting along in neutral? Was this feature an option or did all 32-34 Dodges have it? How similar was this mechanism and operation to FREE WHEELING? Did any other cars of this era have this feature? Please forgive all the questions. I'd never known about this before, and find it facinating.

thanks so much,

Rob

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Rob, if I follow RAH's explaination correctly, the clutch wouldn't disengage going down a hill. I think the car has to be sitting still for this to work.I was thinking along the same lines as you until I rread RAH's post.

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Ron; The vacuum(automatic)clutch option worked in conjunction with the free wheeling option. The car can be driven as a standard shift or in freewheel without using the clutch pedal. The on/off switch you ask about is the freewheel knob on the dash panel. Pull it out and the freewheel is off, push it in and the freewheel is on. The 34 Dodge trans was in the same family of design as the 32 PB Plymouth, 33-34 Plymouth and 33-34 Dodge. Some early 33 Plym PC's and all 34 Plym PG's came without the freewheel capability. All 33 and 34 Dodges had the freewheel capability. Most 33 Plym PD's and most 33-34 Dodges came with the auto clutch but it was always listed as an option. Many marquis came with freewheel between 31 and 35. It was a poor attempt at overdrive. Your question about the car "drifting along" opens up the key problem with the freewheel design. You cannot shift out of freewheel unless the car is brought to a complete stop. Many people died on mountain roads while in the freewheel mode. With no back pressure from the engine, to slow forward progress, cars became out of controll. In my personal opinion the freewheel lever should be disabled at the transmission case. In fact there were 3 states that outlawed the use of freewheel, because of this issue. The other down side is the vacuum power it needs. Vacuum used for other that engine function is a loss to performance and lethal to the health of exhaust valves and seats. You are essentally sucking cold air into a very hot chamber that is full of precision metal parts. Warping and cracking will follow in time.

Jim Cook, 33 Dodge DP technical advisor DBC

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In 1962 my dad bought a 1935 Dodge with an automatic clutch. I drove it a few times & remember the prominent chrome knob on the dashboard to engage/disengage the freewheel. When the automatic clutch began giving trouble, dad removed the mechanism & took it to the local Chrysler dealers to see if he could get replacement parts for it. They couldn't help him with the parts, but the guys at the dealership were fascinated to see the mechanism. I have attached a photo of dad standing alongside the car outside his sheet-metal factory in Fitzroy (Melbourne, Australia) in 1962.. 

Alan & 1935 Dodge at 96 George Street Fitzroy 02.jpg

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I have a 1934 Dodge which has the Free Wheeling setup. Basically on mine there is a control knob on the dashboard ( see the pic ) ....the big one in the middle with a button in the centre. This is attached to a cable as you can see in the second photo. This is the attached to the gear box and enables you, once engaged, to change gears without putting the clutch in. The only problem was that people forgot to disengage it and the car kept on going. The black and white photo is a 34 in the showroom. Zoom in and have a look under the spare wheel on the ground. Notice anything ???.....I believe they disconnected the free wheeling cable to prevent potential customers killing themselves on a test drive !

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Note that this topic originated in 2005 so not sure how much interest there is now.

 

Nevertheless just to clear any misconceptions on the topic, there are two seperate units being discussed here, freewheel device and automatic clutch. Back in the day the freewheel device was  very common around the early to mid 30s in the Chry/Plym/Dodge range, not so the auto clutch, this was generally seen as an extra option and probably less desirable.

 

The auto clutch, as previously stated, worked with a vacuum unit attached to the clutch pedal linkage, it had a control cable operated from a dash mounted handle/button to enable the driver to connect/disconnect the function as required. When selected it would move the clutch pedal under the influence of manifold vacuum and an acceleration/deceleration pendulum valve.

 

Form start you needed to depress the clutch, engage a gear lift the clutch pedal  and get underway, once in motion each time you lifted your foot off the gas pedal the sudden increase in vacuum and deceleration would pull the clutch pedal down and you could shift gears, putting your foot back on the gas and subsequent drop in vacuum plus acceleration would bring  the clutch pedal back up; so the overall operantion meant that you could do most of your driving without having to use the clutch pedal, almost but not quite, an automatic.

 

 The down side to all of  this was, as previously mentioned, if you were decelerating with the intention of slowing down, or going downhill, then the vacuum action would pull the clutch in and you would lose the influence of engine compression braking, for this reason most drivers would disconnnect the unit permanently; when in use it was commonly referred to as being in Angel gear.

 

The freewheel device was something else, built into the gearbox it was simply an over run unit that caused the gears to freewheel under negative engine torque loads, going downhill or with a light throttle load on the level; the engine would drop back to idle and the gears rotated as if in neutral, once again however this could be dangerous with the loss of engine braking. There was a control knob to disengage the device, however it seems most people left it engaged unless going down any reasonable sort of hill, leaving it engaged in normal use was common as it did work  quite well as a fuel saver. 

 

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free wheeling option.

 

i have it on my 33 dodge, but it was never used, I have been told it has caused accidents and did not work correctly by others on this forum. 

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I have a 1960 Rover which has a similar freewheeling option, so the idea was kept going for a few years! You just wind out the knob and can change gear without the clutch and free wheel on 'overrun'. Don't mind it, but of course it's a bit harder on the brakes with no engine braking. (Currently I have no brakes at all, so not going very far, esp. in freewheel mode!)

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19 hours ago, Sactownog said:

I have been told it has caused accidents and did not work correctly

Hmmm. Caused crashes? I really struggle with this. The only cause is lack of braking on behalf of the driver and perhaps a bit of fluster for a new driver of such a car, not expecting it.. Not dissimilar to an automatic gearbox of not long ago; not much engine braking through them either.

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Near as I can tell the big issue was they were troublesome. Someplace I've got a copy of a trade magazine of that era with a how to on adjusting them. As I recall, it took to people: One driving the car and the other riding on the running board working on the adjustments as the car was being driving. I am sure our modern safety codes would have something to say about that.

 

The automatic clutch was missing on my car. I eventually found one and planned on getting it working. The issue that I did not figure out a solution for was the die cast vacuum spool valve that controlled the whole thing was worn out and leaked like a sieve. Based on the total lack of a filter on the inlet and the dirt roads of the time I imagine this was a common failure mode.

 

My back up plan was to install it for appearances only and block off the vacuum line from the manifold to the unit to avoid run lean situations on the engine.

 

But that idea died the next time I did a tune up. On the 1933 Plymouth the timing mark used for ignition timing is on the flywheel (I think they moved it to the crank pulley in 1934). And with the vacuum clutch assembly mounted there was no way I could see the timing mark while hand cranking the engine so I couldn't get it to TDC to properly set the ignition timing. At present the cosmetically restored automatic clutch unit is on a shelf in my garage and it is likely to stay there.

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Having rebuilt and installed the Auto clutch on my CB Chrysler, my recommendation to you is leave yours on the shelf.

 

Perhaps you can take it down every so often, dust it, admire it, maybe even show it to your buddies as a conversation starter at you next BBQ, then put it back on the shelf where it belongs. 😉 

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Would anyone like to buy one of these vacuum clutch units? I have one I got in a box lot a few years ago. Unrestored, as found, complete with "patina". I recognized it from having one on a '34 Chrysler Airflow I once owned. Very unusual accessory and ideal for the uses hcris and ply33 suggest. :) Anybody??

.

 

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19 hours ago, 36 D2 Coupe said:

Would anyone like to buy one of these vacuum clutch units? I have one I got in a box lot a few years ago. Unrestored, as found, complete with "patina". I recognized it from having one on a '34 Chrysler Airflow I once owned. Very unusual accessory and ideal for the uses hcris and ply33 suggest. :) Anybody??

.

 

How much I still have the mounting pin on my 34 Dodge for it you have all PCs? Linkage, that mounts to gas pedal swivel ect ?

 

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3 hours ago, knobless said:

you have all PCs? Linkage, that mounts to gas pedal swivel ect ?

 

Just have the main body of the unit which looks complete. Coated with the usual residue you would find in the engine bay. But no linkage. You would have to make that up in cooperation with someone who has the whole thing and can supply pictures and measurements. I think the cylinder is stuck and I have not tried to free it. Sending you a PM.

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