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1950 DeSoto semi automatic fluid drive questions

Discussion in 'The Hokey Ass Message Board' started by Wilf13, Jun 19, 2011.

  1. Wilf13
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    Wilf13 Member

    I have a 1950 DeSoto DeLuxe Club Coupe (S-14-1) with fluid drive and the semi automatic gear box (low and high gearing with a clutchless overdrive engagement).

    I have some questions about the (correct) workings and maintenance.

    First of:

    When I lift off the accelerator it grinds into the overdrive. It sounds like someone wrongly shifting a manual box. This sound take about a second, sometimes longer, then it's in overdrive and can step on the gas. Sometimes though, it will not shift all the way trough and just grinds when I step on the gas. I then have to clutch or else I am powerless. My guess is that isn't normal and should be adjusted. Can I adjust this somehow?

    Next question:

    When driving in low (3rd of 4th) and stepping on it, it has a lot of slippage in the beginning. Could this be the fluid drive coupling or is the clutch almost dead? How much slippage must it have?

    Last questions about the Fluid drive:

    How can I maintain the system? Should I be filling the Fluid Drive somehow? Or how can I check the right amount? Cannot find this in the manual I have (see next question).


    Overall question about maintenance:

    I have a '49 Chrysler workshop manual (with C45 through C50). Can I use this for my '50 DeSoto or are there some significant changes between '49 and '50 and between Chrysler and DeSoto?
  2. LostHope
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    LostHope Member

    might want to try asking your ?'s on this mopar fourm.http://www430.pair.com/p15d24/mopar_forum/...they will have your answers for sure! i think there is a way to check the fluid on the side of trans by taking out a square headed plug and filling it till the fluid starts to pour out then replace plug.... if remember correctly my pop's doing it on his in his 51 dodge coronet...i think you only use the clutch to start out in first then when you let of the gas pedal you should hear a clunk sound when it shifts to second not grinding sound !!thats why they got a nick name of"clunk-o-matic" trans
    Last edited: Jun 19, 2011
  3. LostHope
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    LostHope Member

    i also saw in one of your other posts you were looking for the emblem for your grill....my pops also owns a 1950 desoto he just replaced alot of the emblems he may have the old one and the hood chrome head piece your looking for..they might not be new looking but will fill your hole and get rid of your skull..if your interested i could see if he has them and if he wants to part with them..send me a p.m if interested
  4. Hnstray
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    Hnstray
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    The trans is a 4 speed, 1st and 2nd straight up from neutral, 3rd & 4th straight down. But there is no overdrive. 4th is 1 to 1 ratio.

    The manual you have for the Chrysler should be useful for servicing/maintaining the DeSoto trans.

    As for the upshift, from either 1/2 or 3/4, it should occur without gear grinding when the accelerator is is lifted.........Is the engine rpm dropping adequately upon lifting off the pedal? As I recall, these shift with electric solenoids, may want to check for free movement of the solenoid....if it's sticking when shifting, or not getting full travel, it could perhaps cause what you are experiencing.

    Ray
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  5. d2_willys
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    d2_willys Member

    Does it grind on the 1-2 (low range) or the 3-4 shift (high range) or both? As I recall, the RPMS are important on the shift, but so are the synchro rings. I believe there are at least two synchro rings for 2nd and 4th gears. They could be gone. This is why it is important to know which of the shifts are grinding. Check low range and see if it does it there too.
  6. moparmonkey
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    moparmonkey
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    Good advice so far!

    I'll add that if you're taking off in high range (3-4), then the slippage you're getting at the beginning is just the fluid drive coupling. The clutch is only used when you depress the clutch pedal to shift between low and high range.

    The grinding gears isn't normal. Usually, a pronounced "clunk" is what happens when you lift the accelerator, hence the term "clunk 'o matic".

    Here are a couple websites that explain the M6 semi-auto...

    http://www.allpar.com/mopar/m6.html

    http://www.fridrichdesign.com/dodge/stdtransmission.html

    http://www.imperialclub.com/Repair/Transmission/fluiddrive.htm

    http://www.jalopyjournal.com/forum/showthread.php?t=522273

    And if it turns out you need parts, send me a PM. I have 2 M6 semi-auto's that I can't seem to get rid of. Both have solenoids and everything. I'd send a complete one to you, but since you're overseas it might work out better if I pulled some parts, which I'd be willing to do if you need them. Someone should get some use out of them. Here are mine...

    http://www.jalopyjournal.com/forum/showthread.php?t=405284
  7. jaygryph
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    jaygryph Member

    Man, great info. I have one of these in a 52 dodge coupe I have in my storage lot. I'll bet it would run with some tinkering, oil looks good. I've been debating on if I should scrap it, sell it, or try and make it run to play with. I've tried selling it but the first option is starting to look most likely, which I hate to do but I can't afford to keep the storage lot.
  8. moparmonkey
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    moparmonkey
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    There isn't a ton of demand for the M6's. From a hot rod point of view, they really aren't a great choice. They shift pretty slow, hence the whole "clunk 'o matic" thing. Basically, the only folks that run them are restorers. If you're wanting to hot rod something, this particular transmission is one of the first items to go.

    However, they are pretty solid transmissions as far as strength/durability are concerned. They ran behind the extended bell 331 hemi's (and were the reason for the extended bell).

    But from a performance standpoint, not so much. Slow, clunky shifting, plus its just a strange set up (clutch and a torque converter), and of course, seriously heavy with all the needed parts. The '52 Dodge coupe is a keeper, the stock transmission not so much. But, it will probably work, so it would be a good thing to leave in it if you can get the engine running, especially if you want to sell it. If the oil is clean and the engine spins, it should be pretty fairly straightforward to get it running. And the semi-auto transmission will be fun to drive because its so different, it just won't be fast.
  9. sewman
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    sewman Member

    I have a 48 New Yorker with the same trans,you can start out in 3rd if you want,the torque converter will slip alot,but for a faster takeoff 1st is better.
    Mine shaifts w/a clunk.
    Have Fun
    Bob
  10. Customline Vicky
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    Customline Vicky Member

    My Dad had 51 & 53 Chryslers. I don't remember them having 4 gears. In normal operation you put it in D and took off up to speed & let off the gas & it shifted into high gear. I hot rodded his '53 New Yorker & found you could take off in Lo, wind it up & just stab the clutch & it would shift like an automatic to 2nd & when wound out shift it to D (3d) & you was on your way. It was actually pretty damned quick !!
  11. Hnstray
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    Hnstray
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    There is a fairly easy option to replace this trans IF you can find the parts. I have done this twice over the years, but as time passes the needed parts become the issue.

    In some '52/'53 Desotos and some '53/'54 Dodges fully manual transmissions where available. I have found '53/54 Dodges, both 6 and V8 with straight 3 speed and with 3 spd w/overdrive. Using a stock manual flywheel and the throwout bear carrier specific to these models (it is VERY long as is the trans input shaft) you can bolt in the manual flywheel, clutch assembly, transmission and use the stock driveshaft and shift linkage and you are in business.

    edit: an even easier solution (other than fixing what you have) is to use a Fluid Drive tranny, instead of the Gyromatic (M6).
    The Fluid Drive models had a manual 3 speed box behind the fluid coupling/clutch instead of the partially self shifting Gyromatic. It has a input shaft compatible with the fluid coupling/clutch. In the case of the FD, any shifting has to be done by the driver moving the lever....all the electric stuff goes away, and Fluid Drive trannies MAY be easier to find than the fully manual versions mentioned above and would be somewhat less labor intensive.

    Ray
    Last edited: Jun 19, 2011
  12. Wilf13
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    Wilf13 Member

    Thanks for all the great replies, guys, much appreciated!

    The grinding occurs in both low and high gearing. It also occurs when engaging kickdown, but I stopped trying that; the first cickdown engaged with grinding but the second time it only grinded and didn't engage, ending up with lots of revs... Ouch.

    The shop manual has no list of known problems and solutions for the M6, only all kinds of electrical tests and one hydraulic test. I should drive the car to a local garage to test those things because I don't have a car lift at home. I hope it's as easy as a electrical problem and hope the grinding didn't already cause too much damage.

    @ MoparMonkey: thanks for the offer, I will look into your option after looking for some trannies at this side of the pond. I could send them from TX to The Netherlands but have to see if it is costworthy.
  13. d2_willys
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    d2_willys Member

    Electrically, this sounds like it could be 1) not enough voltage to solenoids from ignition switch or relay if it uses one. 2) upshift/kickdown switches or wiring is causing a reduction in voltage applied to the solenoids. One way or another, sounds like the solenoids are not getting enough voltage to them. They need to snap hard when actuated.

    This is electro-hydraulically operated, so there may be a hydraulic problem with it. A pressure check would tell you more. Not enough pressure would cause engaging of the gears to be somewhat slow causing grinding. (I am thinking this is the problem)

    You got me interested, I will look into this matter tonight, as I have some good books on this thing. (BTW: My father had one in a 53 Windsor, and a friend of mine had one in a 50 Chrysler Royal, so they are all to familiar)
  14. plym_46
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    plym_46 Member

    There are several items that need to be in complience for a smooth shift.

    There is a governor, that senses the speed of the vehicle to dtermine when to shift, and the is the solenoid that signals the trans to shift. Both have contact points in thier mechanism. if the points are not opening and closing properly it will effect the quality of the shift, as will the condition of the connections in the harness. First thing to do is clean and tighten all contacs and terminals. Also there is apart of the wiring harness that serves two purposes. One is it connects to a dashpot on the carb that keeps the rpm frm dropping too fast as you slow down in anticipation of the kickdown or coming to a stop. Then it also connects to the coil and momentarily interupts the ign to provide some drive line slack to allow the shift to happen without pulling against a load.

    The link to the Imperial club repair area is a great tool for trouble shooting and adjusting. The mechanics technical bulletins are a great resource.

    Also you might want to send a PM to Hillbilly4008, as he just went through his system in his 53 Desoto to good effect.

    As a bit of info the fluid drive is not a torque converter until 1954. Prior units are merely a fluid coupling that was used to drive several different transmissions. It is about 98% effective with transferring engine power to the trans, but no torque multiplication till the later years.

    Never ever heard of any one ever blowing one of the semi auto up from working it to hard, so for a cruising car they are pretty bulletproof once adjusted and operating properly.
  15. Wilf13
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    Wilf13 Member

    The Imperial website is more than valuable, this is great info, lots of maintenance and problem solving.

    On there there is a diagnostic of the fluid drive tranny. It says in the text that slow upshifts are most likely a throttle linkage or a piston problem. The throttle linkage is behaving perfect.

    One thing I forgot:

    There is a sound when driving, I believe in the second and fourth only but not sure, it sounds like a solid metal rod bouncing over the ground (a bit like the rattle of a BIC pen when ticking on a solid table.
  16. d2_willys
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    d2_willys Member

    You sure about the years, I believe they were using torque converters for several years before using it with Powerflite.

  17. Hnstray
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    To the best of my knowledge, all the Mopar semi-automatics used fluid couplings, not torque converters..........much the same as early Hydramatics...no torque multiplication there either. Only when the Powerflite and Torqueflights came along did Mopar use torque converters.

    Ray
  18. oldcarfart
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    oldcarfart Member

    Taking your car to a local garage, unless they know old MOPAR stuff will leave you very unhappy and it will cost a lot. Hook up with local MOPAR clubs, etc.
  19. Wilf13
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    Wilf13 Member

    I never go to a normal garage, don't worry. My 'garage' buildt drag race cars and he drives US cars from the fifties. He knows his way around. I also have a car shop manual and he is not so stubborn not to use it when he would have to. He's a brilliant technical guy and a good friend.
  20. d2_willys
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    d2_willys Member

    According to allpar.com, the 51-53 Chryslers used fluid torque drive, which had a converter. Also Plymouth Hy-drive for 53, 54 used a torque converter. (Powerflite, I believe, started out using the converter from fluid torque drive, but later changed from two stator type to single stator type.) Dunno what Desoto and Dodge used, although Gyromatic comes to my mind.
  21. plym_46
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    plym_46 Member

    fluid torque drive was not a converter it was an impellor and stator tha this not multiply engine output. So call me a lier for a year.

    tiptoe, (desoto) simplimatic (chyrsler) gyromatic (dodge) and truck o matic (swear to god, dodge truck) were all actually M6 electro hydraulic semi automatics. Earlier versions were M4 varients, Plymouth for about a year and a half in 53 had the Hydrive which was a 3 speed transmission, behind a torque converter. The powerflite introduced in 54 and featured a torque converter. Early models were shifted by a dash mounted lever (like the later Corvair) then in 56 push buttons were introduced. Rule of thumb, semi with a clutch pedal no torque multiplcation, automatic with two pedals TQ in place Also had what would be considered a shift quadrant style gear selector.

    Fluid torque drive was an option which introduced the concept of torque multiplication throughthe use of pressurized oil. So It may have been considered a Torque converter Lot of splitting hairs in the mopar engineering annuls.
  22. Wilf13
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    Wilf13 Member

    I read in the manuals via the Imperial website that the shifting occurs when the throttle linkage is at idle (foot off gas) but this is where I guess the trouble starts: the throttle linkage itself is behaving as it should, springing back nicely, but the engine itself is very slowly diminishing its revs. Could that be the off sync-problem? How can I get the engine to respond faster? I guess it's down to a worn engine.
  23. d2_willys
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    d2_willys Member

    I know you said it springs back nicely, but is there a dashpot that might be misadjusted? Might look into that.
  24. plym_46
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    plym_46 Member

    There is a dashpot that keeps the idle up, but it is usually involved with keeping the engine from stalling from dropping to idle to quickly in relation to the fluid drive unit. there should be a circuit that grounds the coil when you lift the pedal to put some slack in the drive line to help the shift occur.
  25. Wilf13
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    Wilf13 Member

    Alright, I'll follow the wiring as it is now and see if anything's wrong or missing.

    By the way: How can I remove the dashboard on the left side (headlight switches etc.)? There are two screws on the lower side of the face but I think I have to remove the buttons first. They seem to have a sort of allen screw inside but no allen will fit in it and the hole seems rounded. Did someone screw them up or is it another sort of system?
  26. CaptainGTX
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    CaptainGTX Member

    Seems like there's at least a little misinformation is this thread. Dodge first started using a torque converter in front of the M6 transmission with the 1953 models. It was the top end transmission option in my very early (built Oct 1, 1952) 53 Coronet convertible. Dodge called it Gyro-Torque. You could still get the Gyro-Matic in 53 but it only had the fluid coupler, hence no torque multiplication. I've driven both, and the torque converter does make a difference, allowing starting out in 3rd instead of 1st.

    On to the original question. My Gyro-Torque had the same grinding when shifting, both up & down. I could minimize it by disengaging the clutch. I found someone locally with lots of experience with the M6's and he diagnosed it as a worn synchro. After a several month parts search, he now has the tranny apart and, if I understood correctly, the brass synchronizer ring had missing teeth. Had to pay $125 for just the part, but what's a guy to do? It will probably pale compared to the labor to replace it. I should have my car back next week.

    Good luck, but if everything else checks out, suspect the synchro.
    Last edited: Jun 27, 2011
  27. Wilf13
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    Wilf13 Member

    Thanks, it is definitely a syncing problem so the synchro was also suspect in my eyes. I got another tip from someone owning a '41 Soto this weekend. He told me it could also be the oil inside the gear box. There's a label literally screaming out loud WARNING! USE 10W MOTOR OIL ONLY! but if someone threw in 80w90 or other gear oil the system cannot move freely enough to shift. I do not have my own garage lift so I'll be checking that out a.s.a.p. at my friend's garage. I hope that could be it (it helped with the '41 owner that had the same problem) but it is a long shot.
  28. Wilf13
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    Wilf13 Member

    I'll use this topic for my driving project if I may:

    How can I remove the dashboard on the left side (headlight switches etc.)? There are two screws on the lower side of the face but I think I have to remove the buttons first. They seem to have a sort of allen screw inside but no allen will fit in it and the hole seems rounded. Did someone screw them up or is it another sort of system?
  29. Wilf13
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    Wilf13 Member

    Some more questions:

    1. My 1950 DeSoto has a 'safety clutch'. The pedal is about halfway lower than the brake pedal and has no play.

    In my 1949 Chrysler I have a fluid drive and I think an M6 (semi automatic) also because beneath the tunnel (from the plate inside the car) I see two solenoids. This car though has normal round pedals and the brake and clutch pedal are on the same height. Are both conditions normal or should the DeSoto clutch pedal (the 'safety clutch') be as high as the brake pedal?

    2. My 1949 Chrysler Fluid Drive (the device itself) is completely empty. I found the plug where to fill it, but how could it be empty? Where can it leak? Also, when I run the engine it rattles very loud. Is this because it's empty?

    3. The 1949 Chrysler seems to burn or throw out the engine oil somewhere at the exhaust manifold. The engine itself purrs like a kitten. But after only a few minutes of idling the oil level changed from right in between fill and full just a little more than full... What could it be? I filled the engine with 20w60 API SC/CB to in between fill and full.
  30. plym_46
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    plym_46 Member

    Does your oil smell of petrol??? If so you may have a ruptured diaphram in the fuel pump and it is filling the sump with petrol. Not Good.

    The safety clutch on the later models usually indicated a torque converter equiped car as opposed to the regular fluid drive. The only place the Fluid drive can leak is the fill plug drain plug or the center seals. If empty you can use unitversal tractor hydraulic fluid to refill it.

    Take a look at the transmission information on the Imperial club website in teh repair section, just to be sure the fluid torque drive assembly is compatable with the universal hyd fluid that can be used it the stadard fluid drive. I believe the design of the safety clutch was to minimize its presence so the transmission was treated mor like an automatic.

    AllPar.com also has some good information also use the esarch for the type of trans you are interested in.

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