Fluid drive dropping out of 2nd & 4th

[Rubbercooke]

My 49 Windsor drops out of gear shortly after warming up at highway speeds. I disconnected the solenoid and drove with same results. I removed the interrupter switch and see

The piston push forward but it doesn't stay when up on blocks running. The fluid is full and correct. The piston looks like the pressure keeps dumping because it releases rather quickly. The car was performing great up until this occurred.

Any suggestions rather than remove?

Thank you

[casper50]

I've never seen a 4 speed fluid drive but I'm fairly new to old MOPARS.

[Don Coatney]

Fluid drive is simply a fluid coupling not a transmission. This topic has been discussed in depth recently. Do a forum search. Where in North East Ohio are you located?

[rb1949]

Hi, glad to see another 49 Windsor. A little looking on the M6 trans will find some great reading and simple troubleshooting techniques to test the 5 electric components that make it work. (Imperial Club and Chrysler Master Technician manuals, all on line)

[DonaldSmith]

Does "dropping out of" 2nd or 4th mean that it upshifts, but then downshifts again?

 

Just a note:  Do you start off in 1st and have it upshift to 2nd? If so, why?  1st gear is "stump puller" gear.  With the fluid coupling, the usual mode is to start off in 3rd and have it upshift to 4th.

 

(This doesn't answer your problem, but that didn't stop me from chiming in on a tangential issue.  That's the fun of this site.)  

[Rubbercooke]

I'm in Ashtabula County near Rock Creek. I've gone through my manual and read the master tech Chrysler manuals. The problem solving really only takes you to the electrical or hydraulic direction but doesn't cover much on the hydraulic side. I will do more searches here to see what I find. My problem doesn't go away with all electric removed from the tranny though.

Thank you

[Rubbercooke]

Donald, no I typically only use the high range but I thought I would try it in low and low drops out as well. When I take off after setting a day or so the car will shift up one - two times then drop out of 4th and not go into 3rd until the car speed falls below at least 30 mph. After it drops into 3rd it will rarely shift back into 4th.

I hope this explains it better. I removed the solenoid wiring with the same result. I removed the switch from the top of the tranny, jacked up the car to observe the piston through the switch port. You can see the piston move forward but usually comes right back and it's like there is a valve opening and closing.

[dpollo]

Loss of fluid pressure will result in a downshift     2 to 1  and 4 to 3.    However you are getting enough pressure to make the initial upshift  1 to 2  and 3 to 4  so something in the transmission is causing the pressure to drop. The removal of all electric control suggests the problem is internal, like a bad pump.  Before you tear into it try a heavier oil  like 30 and see if it causes the problem to go away.  It is not a cure, but would be an indicator of a worn pump or leaky seals.

[Rubbercooke]

I did try heavier oil with no luck, same results. The way the piston pushes back it looks like a valve is dumping but I've checked the only 2 I could acess.

[mopar_earl]

Pull, clean and polish the pressure relief valve. Make sure the solenoid isn't sticking keeping the ball from fully seating. May have to pull the trans apart and clean the pump suction screen. Pump could be weak.

Earl

[DonaldSmith]

I looked at the diagrams for the M6 transmission.  The hydraulic circuit seems very simple.  

At low speed, a ball valve dumps the oil back into the case.  Pump fast enough, and the pressure builds, the ball valve is pushed closed, and the transmission upshifts.  Slow down, and the oil is dumped, and it downshifts.  This is ignoring the solenoid.

There is also a "shuttle valve" at the pump.  I guess this is to relieve pressure at high speeds. 

So, one of these valves may be the culprit.  That's my guess.   

[Rubbercooke]

Is the pressure relief I the bottom rear plug under the tranny? There was a plug I removed and looked over but didn't notice anything that would allow it to bypass. Is the screen only accessed from the inside?

[Rubbercooke]

I did notice fluid squirting from the plug adjacent from the solenoid on top of the tranny. I looked over the ball valve under the solenoid and parts looked good and in proper order. The lower valve also looked good although the spool that is the last to remove would not come out. I never thought about the coil plunger pushing the ball from not retracting enough. I will check it after work tomorrow. Thanks again!

[rb1949]

Always like to read what people are doing, finding, or solving problems with this M6 trans. Keep us updated.

[Rubbercooke]

I will, been too busy last few days. Hope to get into it by the week-end.

Thank you

[Rubbercooke]

I removed the drive shaft from the transmission and separated the case around 2", rotated it and found the filter which was plugged almost solid. I cleaned the screen, flushed the bottom of the case as best I could and struggled to put the case back together but finnaly managed. Filled with fluid, took a drive and it performed perfect. Thanks for all your help!

[mopar_earl]

I removed the drive shaft from the transmission and separated the case around 2", rotated it and found the filter which was plugged almost solid. I cleaned the screen, flushed the bottom of the case as best I could and struggled to put the case back together but finnaly managed. Filled with fluid, took a drive and it performed perfect. Thanks for all your help!

When I had mine apart to clean and reseal, my screen was mostly plugged. Many years of nondetergent fluid had took its toll.

Glad it was a simple fix.

Earl

[rb1949]

An interesting fix, not exactly simple. Not sure I understand where this filter is. Pictures by chance?

[mopar_earl]

An interesting fix, not exactly simple. Not sure I understand where this filter is. Pictures by chance?

Much more simple than needing a complete rebuild or trying find a good used trans or converting it to a manual trans.

Earl

[rb1949]

In comparison, true.

[Rubbercooke]

After the drive shaft remove the bolts (maybe 6-8) holding the back half to the front. Separate just enough to rotate the back half ccw and on the front half lower left looking toward the front it looks like a recessed cup (mine was full of junk) and when I used a screwdriver to work out there was a strainer attached. Cleaned up like new. From the drain plug I flushed through the screen port all scum from bottom of case too. Sorry no pics though.

[DonaldSmith]

The M-5 has a removable cover over the filter.  They must have saved 5 cents per unit on the M-6's.

 

 

(The cover is that lozenge-shaped plate with two bolts, partially obscured by the parking brake cable fitting.)

 

The M-6 has to have the cases separated.  Bummer. 

 

Maybe I'll check my filter. 

Edited July 30, 2016 by DonaldSmith

[Dodgeb4ya]

Shown are some location pics of the tubular oil strainer located behind the extension case in the 1949 and up M-6 hydraulically operated transmission.... 

1942 to 1948 M-5 transmissions have a small easily removed cover plate to service this same filter as shown above.

If there is a lot of brass/steel debris in the filter it's a sign of a lot of wear on the direct speed blocker ring /sleeve  and free wheeling roller retainer, and input shaft.... high wear parts if the trans was not serviced well meaning good fluid and always topped off full.

Bob

[Rubbercooke]

If anyone is looking for parts let me know. Free, you pay postage/shipping. I took a 50 tail housing off and swapped on my 49. Pretty straight forward and shifts very quiet and smooth. Let me know if you are needing 49 or 50 and what your looking for.

Thank you