49 Fluid Drive advice needed

[rb1949]

Time to check some things on the 49 Chrysler Prestomatic M6. Don't think it's working properly. Have never ridden in or driven one that works normally to get the 'feel'. Help where you can please. Starting with a simple fluid change, recommended 10W. Found the access plate on the hump. Bottom plug to drain, top plug to fill. Confusing capacity already. Manual says semi-automatic, 3 pints. That's it?? Fluid Torque Drive is 10 1/2 qts. Is that the converter? Most say don't bother with that.

The manual, and copies of several posts here with tips, will attempt to diagnose the electrical components. The wiring diagram has 6 things, but not where they are located. An 'anti-stall' switch & 'kickdown switch' ..... carburetor? A circuit breaker/resistor 'box, which is on the fender well going to the ignition. Now there's a 'solenoid switch', a 'governor', and an 'interrupter switch'. Are these on the tranny? The attached picture shows 3 things wired in there. Which is which? I guess you can disconnect certain things to evaluate if they are working. And/or check the component itself, some have points that may need cleaning? If you know of a post with testing advice, please provide that. Any pictures of this stuff too. I'm really in the dark here, but ready to give it a try. Thanks if you can keep it simple.

[dpollo]

It is simple if you take things in order.  

 

The fluid coupling is a separate unit and can be drained and refilled if needed but it is rarely needed.

 

The Simplimatic or M6 transmission uses #10 engine oil  ATF would work.  It has two speeds in two ranges (4 in all) It effects shifts within the selected range by hydraulic pressure .  It will work without any electrics, but will not downshift unless you come to a stop.

 

The electrics allow a downshift by dumping hydraulic pressure and briefly interrupting the ignition to break torque. A solenoid on the carburetor enriches the idle circuit to prevent stalling when idling in gear.

 

To drive, you select the range , and release the foot clutch.  When sufficient speed is attained, release the throttle and the transmission will shift into the upper gear of the range you have selected.

 

If a change of range is desired it may be done  while moving by pushing the clutch pedal down and moving the lever. Avoid using the foot clutch except to move the lever.

 

If kick down is required, depress the throttle and the electrics will do the rest via a switch on the carburetor.

[greg g]

Go to the Imperial club website repair section for all the information you need to keep your

M 6 in proper working order.

[rb1949]

The Imperial Club manual is my reference. Seems like it would hold more than 3 pints. HA. Find 10W! Will check a tractor place nearby, heard of "TDH" fluid? Heard not ATF. Now to identify the pieces on the tranny and what they do.

[bobostski]

In My 49 Chrysler, the M6 will not shift unless I'm going between 25 and 30mph. Is this a normal range?

[dpollo]

A shift point as high as 25 mph is not normal,  fluid pressure may be low.

 

as for the letters ATF   automatic transmission fluid.   Nothing exotic, just light oil.  

[50 Dodge Lug Nut]

rb1949 -

 

These transmissions, once you figure them out and get them set properly are bullet-proof and literally flawless. And fun to use, if rapid acceleration is not your game.

 

First, recheck your fluid levels and what /which of the transmissions "drain/fill plugs" you are using. It's likely the transmission is over-full. The top most plug is for the shifter-forks & lock screw.

PLEASE don't make the mistake of thinking that's the filler plug because that would be too full. Ask me how I know.....

The middle plug  is your filler plug & fluid --similar to checking your rear differential level. Fluid should be at the bottom of the hole--

obviously, it can't go any higher.

The bottom plug is your case drain plug, as you stated.

 

Now check your governor. There should not be a lot of oil in the governor switch. Learn how to clean the insides. 

 

Next, double-, triple,check your idle speed. Best speed idle is between 450-500 rpm, max. A tach, might be lying to you. Set the tach aside, and turn the idle down as far as it'll go and still run -- just fast enough that it'll idle in gear without stalling. I'm mean really low. See if that makes a difference.

 

Hope these tips help you.

 

Frank

 

[mopar_earl]

Also make up a new harness for the transmission. Mine was beyond shot and couldn't believe it started, ran and shifted. Couple of my connectors was only on by a couple wire strains. Also clean your connections as well.

Not sure why so many ppl dislike these semi-auto transmissions. I love mine, just wish it had an OD.

Earl

Edited June 12, 2016 by mopar_earl

[Dodgeb4ya]

The M-6 Transmission capacity Is 3 Pints of 10 weight oil.

 

The "Fluid Drive Coupling" capacity is not easily found because the fluid was not to be changed and should not be IMO. Just make sure it is full by rotating the coupling till it is accessible through the floor access hole..top off with 10 weight oil or universal tractor fluid. The fill hole is tiny...3/8". No second drain hole is provided so don't.

The Fluid Drive coupling has nothing to do with the transmission operation/ shifting etc. It normally never needs anything done to it.. just check fluid level.    And no you can not easily find "MoPar Fluid Drive Fluid"

 

Fluid Torque Drive is an actual torque converter found only in 1951 and later chryslers as an option except on Crown Imperials....was not available on 1949 or 1950 Chryslers.

 

A couple pics of access and fill plugs etc..

[rb1949]

Thanks for the pix identifying the 3 parts on the tranny. Found the 10W. Out there now, unit is drained. DO you FILL IT from the TOP PLUG, and stop when it starts coming out the center plug??? Looking at the wires too, and a re-wire may be on the list. The solenoid & governor can come off? (unscrew?) Only the governor can be opened for cleaning.

 

edit: Got the meter out, and studying the procedures for electrical testing. Just can't tell wire colors.

 

edit 2: Black fluid. Tranny will appreciate fresh. Fill complete. Not sure, so used a hose into the center plug. 3 pints. Maybe I should run it a few weeks and change again? So just what is that top plug for? No fluid to be seen. Can't say it ran any different for a ride around the block. Spent too much time chasing the wires, so no testing. 5 wires at the trans, only 3 wires coming out under the hood?  2 wires to 2 different things on the carb. No colors match. Another day to figure out what's what. I'll be back for sure.

Edited June 12, 2016 by rb1949

[Dodgeb4ya]

Fill ithe trans through the side fill plug till it runs out.

Just pull the governor cover off...4 slotted screws. Clean the cover and  silver contacts with contact spray cleaner. Be careful not to use a file on these contacts..they are soft silver.

The solenoid and governor do unscrew but no need to remove either unless the governor is full of oil... never seen that.

Governor Pics...   1946-48 M-5 cover shown but the same as the later M-6

[rb1949]

More good pix, thanks. Many of my questions are trying to confirm what I see/read before proceeding. The old brain needs that extra help. (Instructions to test - clean - adjust things don't tell me where to find the component.) (And I would have filled to the top plug!). Something simple in there. How can that be?? So what is inside that canister, oil? Moves points by pressure? I'll soon find out. Will get out jumpers and attempt testing before taking apart. No color match, so may have to chase each wire first to see where it goes via diagram. Frightening question, if any of the components are bad, where does one find working replacements? Learning slowly about the old jalopy.

[Dodgeb4ya]

The 1949-50 chrysler blue shop manual is how I learned all about this transmission back in the early 70's.

It's good reading. It tells it all  and correctly.

Edited June 13, 2016 by Dodgeb4ya

[rb1949]

Cool. "Blue" is on my watch list.  Assuming that would be different from the Imperial Club manual, which has been printed. (A lot of pages!)  Figured out the 5 wire at the trans but 3 wire at the other end mystery.  3 of them are hooked into one. All black. Can finally trace each to destination, and measure for new harness. Want to disconnect all and do a short drive. Says that only affects the downshift?

[Dodgeb4ya]

With out the wiring connected to the transmission it will up-shift immediately when you get going and let up on the gas pedal. Then It will stay in the upper gear of what range  (low or High) you selected until you come to a complete stop and push the clutch in and wait a few seconds for oil pressure in the trans to drop... then you will feel or hear it pull back into the lower gear.

Do not shift into reverse unless the trans is for sure in the downshifted gear.

 

If the transmission does not up-shift with out the wiring to it connected the idle speed is too high or it's low on trans fluid or there is an intenal mechanical issue.

 

Bob

Edited June 14, 2016 by Dodgeb4ya

[Phil Martin]

I had trouble with mine dying and not starting. I unhooked the wire from coil to circuit breaker and it starts great. I can take off and then push clutch and it will upshift. Possible have a problem with interuptor switch? Haven't looked into that yet. If yours wont shift til 25 mph the idle is to high.

[James_Douglas]

"The "Fluid Drive Coupling" capacity is not easily found because the fluid was not to be changed and should not be IMO. Just make sure it is full by rotating the coupling till it is accessible through the floor access hole..top off with 10 weight oil or universal tractor fluid. The fill hole is tiny...3/8". No second drain hole is provided so don't."

 

This is just wrong information.  Seems like I have to post this every 24 months as people don't search before the ask new questions...

 

The M6 capacity is 2.5 unless you have taken the rear off then it is 3 by the way.

 

*************************************** Fluid Drive Fluid Tech Note *************************

 

Technical Note on MOPAR Fluid Couplings

 (Fluid Torque Couplings are NOT covered by this Technical Note. Copy/Publish at will so long as you copy the entire note.)

By James Douglas – San Francisco

 

 

Having run several types of oil in MOPAR “Fluid Couplings” over the years and heard many recommendations, I decided to see if I could approach the issue of what lubricant to use in one of MOPAR’s Fluid Couplings by a more scientific method.

 

As is well known, Chrysler instructed all owners to use “MOPAR Fluid Drive Fluid” only in their Fluid Couplings.  Problem is, MOPAR stopped making it decades ago.

 

My first stop was Chrysler Historical.  After a month of looking, I was told that they do not have any of the original engineering information as to the specifications of the fluid.

 

Then I headed off into internet land to hunt down anything I could find on the subject from ORIGINAL sources.  I managed to find an original Chrysler Question and Answer sheet from 1939 about fluid drive from Chrysler Engineering.  In it they stated:

 

“…The proper fluid is a low viscosity mineral oil, which also servers to lubricate the bearing enclosed in the coupling. The pour point is such that the oil will pour at the lowest anticipated temperature, and has no corrosive effect on the steel parts of the unit.”

 

All well and nice, but not enough to figure out exactly what they used as fluid.  Later in the same document they talk about the types of metal used and the carbon-graphite seal.  Hum, carbon-graphite seal. 

 

I did some more digging for a few months and turned up a can of unopened original MOPAR Fluid Drive Oil.

 

An analysis of that oil, and some more literature I ran across, stated that the original fluid was a pure-base mineral oil with a Saybolt Viscosity of between 100 and 150. The fluid had a Viscosity Index of greater than 80.

The fluid had anti-foaming and anti-oxidation additives. It specifically did NOT have any seal swelling agents as these can attack the carbon-graphite seal and the copper in the bellows. This last specification eliminates most modern transmission fluids.

After finding several formulas to convert Saybolt Viscosities to Kinematic Viscosities, it appears that the best match to the original specification is ISO 22 or ISO 32 oil.

However, the ISO 22 is just below 100 Saybolt and the ISO 32 is much higher than 100 Saybolt.

Based on a period (c.1947) Lubrication Industry article on fluid couplings that had the following admonishment:

“Contrary to popular supposition any attempt to use a higher viscosity fluid would actually reduce the torque transmitting ability of the coupling since torque-transmission is dependent upon a high circulation of fluid between the impeller and runner and is not caused by any viscous drag between the two.”

 

During my continued research on the history of the Fluid Coupling, I ran across the fact that the original company that licensed the fluid coupling technology to Chrysler is still in business and still making fluid couplings for industrial applications. 

 

After a couple of weeks of digging, I found a senior engineer from that company that would have a long technical talk with me on fluid couplings.   In essence, he agreed with the period information I quoted above.  He added that the lowest viscosity oil that would still provide for bearing lubrication is the one to use in theory.  However, he did say that unless the fluid coupling bearing has been replaced and is know to be very high quality then err on the heavy side viscosity wise.  Just don’t over do it, he stated.

 

I was also told that normal hydraulic fluid does not have large amounts of anti-foaming agents in them as they usually do not have large amounts of air in the systems to foam in the first place. 

 

A fluid coupling is only filled to 80% and as such has lots of air in it.

 

Therefore, when looking for fluid coupling oil, one must look for an oil that is a “Circulating Oil” which has a lot of anti-foaming additives in it.

 

I was also informed that the additives tend to have a shelf life in the can, or in use, of 5 to 7 years and it should be changed at that time.

 

I was also told that the couplings are actually somewhat permeable and water vapor will work its way into and then back out, when hot, of a steel fluid coupling. Very little amounts, but apparently is does go on.

 

I was also told to never use engine oil or ATF as both would cause problems in the long run.

 

Based on the research and discussions I have come to the conclusion that ISO 32 hydraulic oil with the proper additives and VI (Viscosity Index) above 80 is a suitable replacement for the original MOPAR fluid drive fluid. ISO 22 would be a better exact match, but only if the quality and condition of the bearing is know in a particular coupling.

The oil I have identified that meets the specification, with a higher general viscosity to deal with the age of the bearings, is: Mobile DTE light circulating oil ISO 32. This oil is available at Granger. 

 

I have run this oil for about six months in San Francisco city traffic as well as up steep mountains on very hot days.  The coupling works well.  I have noticed, and other car people have as well, that the car seems to move out from a dead stop to 10 MPH better with the fluid.  Only a before and after session on a dynamometer would tell for sure, but I feel that it moves out much faster.

 

Classic car owners are advised to use this information at their own risk.  I am not a fluid coupling engineer, a bearing engineer, or a lubrication engineer. I have done my best to find out what was in the original MOPAR Fluid Drive Fluid. This effort is in essence industrial archeology and should be carefully considered prior to use.

 

As a post scrip in 2014.  I ran across and old Gyrol book that talks about the filling of the fluid couplings.  In short, how much you fill it affects the torque-stall curve.  Chrysler set that by the position of the hole in the bell housing.  However, if one is to fill it a little less or a little more one can change the curve.  Do so at you own risk and never fill it past 90% so it has air in it to compress less you blow the thing up!.

 

James Douglas

San Francisco

[Dodgeb4ya]

Sorry for the wrong information James.

I still say leave the fluid couplings alone. Check the fluid level only-don't change whats in it if it does not leak and works fine.

I  have re-sealed many of these couplings and understand them very well. I have six cars with then too.

I do have a 60 page S&W Tool rebuilders book on these MoPar couplings where my knowledge started back in the 70's..

Nothing really special about these couplings.

If the work leave them alone. 

[James_Douglas]

The engineers that licensed the technology to Chrysler happen to disagree with you. I was with you on the same page until I spent a year digging into it.  More of an intellectual exercise when I cam across an unopened can of the original molar fluid. Once I had it analyzed, read over the period engineering literature, and talked to the engineering VP at Gyrol fluid drives I came to the conclusion that MOPAR did in fact use a particular oil for a particular reason.  The high VI and anti foaming is very important to their operation.

 

The couplings have air in them and any foaming will reduce their ability to transfer torque. Their recommendation is that the fluid must be changed every 7 years or so as the anti-foaming additives degrade in that time frame.  Given the fact that the coupling are now decades old.  The anti foaming agents are now worthless.

 

All I can say is that I noticed a better zero to 10 MPH acceleration with the new fluid.  Of course it would have taken a dyno test with the old fluid and the new to be sure.

 

Of course one can just "leave them alone" and they will work.  Just not at optimum performance.

 

James.

[Dodgeb4ya]

I agree that your'e very intense studies of the simple FD couplings oil requirements can be slightly enhanced by using #32 hydraulic fluids. I do appreciate you studies too.

 

These FD couplings are fine as designed..... sluggish but who's in a rush who owns one...not me!

 

Over the years I have used 10W and UTF will no issues. ATF is an absolute No No. Graphite seal can leak and Bellows pinhole.

 

Most all my FD coupling Chryslers have never had any FD fluid added or changed and never will. They always work fine. I've learned from others messing with them.

 

.Nothing special in these couplings.  Understanding what wears in them is another thing....what can be fixed and what cannot.

Two welds on the housing ( repaired cut open units) and it will probably vibrate! Have seen a couple of these lately.

 

Some FD coupling pics..

[rb1949]

Saw James research findings on another old post. Not sure what to do with coupling, leave it alone. If changing would use 10W, manual says 10.5 qt. (Just pull the plug, then rotate hole to the bottom so it drains out? Slow, with no air vent.)

Hopefully have traced nasty wires from trans to engine compartment, trying to confirm how they are connected now. Remember, no matching colors. One reading may be indicating a short? Not sure if that could mean in the wire, or one of the components stuck in the wrong position. Made a schematic as I went, seems to be matching the wiring diagram. Lots of labels as those 3 wires branch out again up front. Anyhow can build new harness, even using correct colors this time.. Have not done the test drive yet with electrics disconnected. Got detoured replacing front brake HOSES. Local store cheaper than on line order. Need a pedal pusher today to help with bleeding procedure. Bleeding, and no band-aids! Progress report to follow.

[Dodgeb4ya]

Leave the coupling alone.Just check the fluid level in it.

Fix only whats needed to get it running and driving well and put some miles on it before before getting yourself into more trouble.

[rb1949]

Got a short ride with electrics disconnected. Now it only starts out in "4th", Quite slow at that. Before, I at least had 3rd for better takeoff. Shifter up (1 &2), not sure what gear it's in, but doesn't shift. Next will be to remove the governor cover and check inards. After that I'm feeling lost, having not really accomplished anything. Would be nice to identify something that would lead to a solution.

[Dodgeb4ya]

I think you should drive any Dodge, DeSoto or Chrysler car with the M-6 transmission in it so you can understand and know how these hydraulically operated prestomatic transmissions feel and operate.

 

The car cannot start in 4th high gear from a standing dead start until the transmission oil pump builds up at least 35-40lbs oil pressure. To do that the output shaft ( drive line) has to rotate at least 15-20 revolutions to cause the transmission oil pump to build up pressure causing an upshift.

 

So it proves the transmission has the ability to auto shift up into high gear. That's good!

 

Clean the governor contacts carefully and make up a new quality transmission wiring harness  or buy a new one from Rhode Island or YNZ etc.

Use the 1949-50 Chrysler shop manual for the correct wiring diagram.

 

Drive the car.... enjoy.

[rb1949]

Agreed, it would be nice to drive it for a change. This is not shifting in any position now. Takeoff is dangerously slow to get moving. Can start "up" (1) then manually shift down (4).Your suggestions have been on the list, not done yet. Will be anxious to see the results. Or back to where I started. No again, have never been in one that works.