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'53 Fluid Drive Acting Up - Looking for help as to cause

'53 Fluid Drive Acting Up - Looking for help as to cause

Old 10-01-2018, 05:26 PM
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'53 Fluid Drive Acting Up - Looking for help as to cause

I have a '53 DeSoto with the 276 V8 and Fluid Drive (aka... Tip Toe Shift). I've had the car for a few years and all has been working great. Over the course of the last two drives in the car, the car will move from 4th to 3rd gear unexpectedly around 50 mph and cause either the engine to go into high revs or have no gear at all engaged until the car slows to around 35-40 and then with a hard clunk the car will go into 3rd. At other times the car will seem to not want to shift from 3rd to 4th when letting of the pedal per normal at around 35 mph. Not sure but seems to happen a bit more after the car is good and warm and has been cruising for a while. I have not done a check to see if the same behavior happens in Low (gears 1 & 2). These are new issues with the car and it was previously the poster child for how the Fluid Drive should work. Oil level is good. Any suggestions as to the issue? Thanks much... Dave
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Old 10-02-2018, 08:20 AM
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I did a quick search and it seems the first thing you need is a service manual, but there are many articles and threads on forums on this subject.
I will list a few a few that a have found.
Good luck

I hope this helps
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Old 10-02-2018, 08:30 PM
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I'm not too sharp with them... I would Chat with the guys over at Chrysler 300 site.
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Old 10-14-2018, 07:33 AM
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Is your Desoto and S16 or S18 model? The fluid torque drives the M6 "Simplimatic" or "Tip-Toe". This transmission uses a spinning oil pump. Not that different from an engine oil pump. It is driven off the mainshaft in the transmission. It varies its oil flow based on the transmission speed. The faster you travel, the faster the pump turns. Shifting takes place by with the help of shuttle valve and solenoid, at the right time, with oil pressure present, various electrical controls, and you lifting your foot off the accelerator.

I am reviewing my service manual here and will attempt to summarize:

There are numerous systems that should be reviewed to troubleshoot your symptoms. There is a governor with a set of switching points that are opened and closed by use of centrifugal counterweights. There is a solenoid that opens and closes, controlling the flow of oil that forces movement of your shifting shuttle valve. This solenoid will activate the oil flow that forces the shift to take place. This solenoid appears to activated by control from the switches within the governor. This governor is geared directly to your transmission countershaft and also driven by car travel speeds. If this solenoid mentioned is developing an internal short you will likely have shifting problems as oil flow is diverted by this solenoid. It only supposed to divert oil under certain speed conditions. For example under 12 MPH the solenoid is energized and held open as the governor points are held closed. The closed governor points allows electricity to flow to the solenoid and energize it. After the shift occurs, the governor points are held open by faster car travel speeds. The now open governor points disconnects power to the solenoid and the solenoid is de-energized, and closes the oil port. In this situation, pressurized oil is held against the shifting fork. Holding the transmission in the high gear. 2nd or 4th for example. The transmission never shifts on it's own between hi and low range. You manually do that task by manipulating the transmission column mounted shift lever. The transmission only auto shifts between 2 gears. Either 1st and 2nd, when in low range, or 3rd and 4th in high range. These two sets of gears are the same in either hi or low range. You are just manually introducing a single lower gear ratio when you put the column shift lever in low range.

If your solenoid is acting up, it could likely cause oil diversion at will. Not when controlled by the governor. Meaning the transmission may or may not shift when its supposed to. An internal short in the solenoid? Or maybe the wiring for the solenoid? This could be your problem. If your governor is acting up, the contact points could be opening or closing at will. Not when they are supposed to when ground travel speeds dictate so.

There is also a circuit breaker and resistor assembly that acts like a fuse in the event of a an electrical short in the transmission shifting system. Yet to complicate things further, there is also an interrupter switch. This switch kills power to the engine ignition system coil temporarily when you slam down the accelerator to the floor to force a down shift. This why the engine dies temporarily, letting up any power, allowing the transmission to down shift. Based on your description I don't suspect there is a problem with the interrupter switch. It sounds to me like an electrical problem. Affecting the solenoid.

The manual offers good steps on troubleshooting each part and system in the shifting process. If you are inexperienced and not too technical you may need to find a good vintage car mechanic that can troubleshoot well. He/she may need a proper service manual to get it right. I keep three different manuals around here for my 1953 Tip-Toe shift equipped Chrysler. My manuals are invaluable. These transmissions have proven to be reliable and largely trouble free. The Mopar engineers came up with a pretty unique system was easier and lower cost to build than a full automatic transmission. Nobody else that I know of offered this semi-auto transmission other than Mopar.

Last edited by Keithb7; 10-14-2018 at 08:10 AM.
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Old 10-14-2018, 07:32 PM
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RH, Iowan, and Keith - Thanks much for the replies.

For Keith: It's an S16. I am not super technical. But the good news is that I have a very competent trusted mechanic that I use on the old cars. I have the privilege of being able to do the initial trouble-shooting of problems when they come up (if "simple" I try to do the fix myself and if that fails call in the big guns). Or, in instances like this, I try to hit up smarter guys like you all to help narrow the issue before I take the car to his shop. This one is over my head. The information you provided (and the links/suggestions from RH and Iowan) are going to be followed up on. I'm going to look this up further on digital manual I have given info provided. I just got home from playing in the mountains for a week or so and now it's time to pick this topic up again. Much thanks for the support.

Much appreciation to you all! I will post again as the head scratching continues or if successful to relay what the issue turned out to be. In the interim, know I'm open to more advice on this issue.


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