'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

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

https://www.jalopyjournal.com/forum/...stions.600183/
http://blog.oldmoparts.com/fluid-drive-information/
I hope this helps

I'm not too sharp with them... I would Chat with the guys over at Chrysler 300 site.

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.

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.

Dave

Hi Keith: Actually while taking some steps, I have not yet taken deep dive into issue. I was literally going drive the car today to try and further narrow when issue is happening - I'm wanting to sneak out of work to do so (first nice weather day in quite a while here). Then I’ll take to my local expert for further investigation. Per suggestions provided on this sight I did get a "real" shop manual as opposed the the compressed CD version I previously had. And, I actually read it! ;-) The manual similarly suggests possible cause is the solenoid. In digging through spare parts I actually have the solenoid - so lucky there if so needed. I do promise to update once figured out. Similarly, any updates/learning you come by are appreciated. All the Best, Dave.

Good luck with your progress, I'm looking forward to hearing back from you.

Update... Kinda
 

As I mentioned in a previous update, I had the solenoid switch. Today we got "lazy" and decided to just switch out the old solenoid for the new. Same issue.

Here's a better description of the issue after a test drive today:

• Low: 1-2 gears: Off the line fine, smooth/normal shift into 2nd upon letting up on gas, runs in second fine until acceleration is backed off. Then transmission seems to get a bit "confused" ;-) and while still at 2nd gear speeds will jump to neutral then to first and then clunk into solidly being in first or second. Usually first. But is has re-engaged into 2nd on one trial. At least in a few tries, if you stay on the gas at relative high speed for second gear (25-30mph) the transmission stayed in gear, it only seemed to disengage once backing off. I mention this as this behavior was a potentially different in high range (see below).
• High: 3-4 gears: Off the line fine, smooth/normal shift into 4th upon letting up on gas, runs in 4th ok for a distance of a 1/2 mile or so and then even with steady pressure on gas pedal the car slipped into neutral. It did this a couple of time on test drives. It takes slowing down for the transmission to engage again and when it does it's in 3rd. Otherwise, for example if letting off the gas while in 4th, the car can experience behavior similar what was described in the Low gears.

So, overall similar behavior both gear ranges.

My mechanic is setting aside more time to look at this again come next Wed. This will include a more disciplined approach to addressing the issue per the "Service Reference Book: Diagnosing the Hydraulically Operated Transmission" that has been downloaded, the service manual proper, and the input received here, and his 35 yrs of experience but very little with this transmission.

All this said, if the above behavior description could help any of you better help me, I wanted to post the info here.

Keith - Thanks for the video. A quick question after watching your video. I know anything is possible... but - do you have thoughts about the issue possibly being the signal from the governor switch to the solenoid?

Thanks again to all.

The journey continues,
Dave

This is all very interesting to me. I look forward to learning the outcome. So I too can learn more about these transmissions. They are new to me as well. All I have learned, I have taught myself so my troubleshooting experience is limited.

Reading your symptoms has me scratching my head a little too. Reviewing what I learned when I took apart the tranny in the video above, I’m thinking about neutral position. The sliding shift collar that you control with the shift lever moves and engages hi or low range, or the centre neutral position. This has me wondering if you have pin-syncromesh problems?

Also thinking about the main drive shaft direct speed clutch. This is the one controlled by the hydraulic piston. Maybe it is partially engaging somehow? Low oil pressure? Due to oil pump? Or piston seal? Partially plugged oil pump screen? Excessive cylinder bore clearance?

Sorry mostly guesses at this time based on my limited experience.

Regarding your question about the problem possibly being the signal from the governor switch to the solenoid. It could be. The solenoid opens or closes oil flow & pressure to the hydraulic piston. This piston moves forward and back, either engaging or disengaging the direct speed drive clutch. Shifting gears between either 1&2nd or 3&4th. The solenoid is controlled by the governor, which is actually controlled by ground speed.

There is a lot of related systems working together here to make all this function properly. I really look forward to learning what your problem is here.

I know of a tranny rebuild expert who is giving out great advice on-line. He’s over on the P15-D24 website. “Dodgeb4ya” is his ID over there. Extremely helpful.
See my thread here: http://p15-d24.com/topic/48916-help-...-transmission/