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M-5 and M-6 transmissions, any difference?


MarcDeSoto

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I have an M-5 semi-auto trans on my 1948 DeSoto.  In 1949, DeSoto, Chrysler, and Dodge used the new M-6 transmissions.  These transmissions are very similar in function.  The only difference that I can see is that the M-6 transmission has a different type open circuit breaker relay, and the M-5 transmission has an enclosed black box relay.  Another difference is that the M-5 solenoid has one wire going to it, and the M-6 solenoid has two wires.  I guess this was to simplify the electrical harness somehow.  Are there any other differences in these two transmissions such as gears, input shafts, interrupter switches, etc?  

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I too am interested to learn the actual differences. 

 

I did notice that a 1953 M6 tranny that I disassembled had a pin-type synchronizer.  In a 1953-54 parts book I have,  they list two types of synchronizers. "Pin type" and "Strut type"

 

It appears that in the later years of the M6 tranny they utilized the Pin-Type synchronizer. A 1954 service manual states: "A number of other changes were made in the transmission in order to use this type of synchronizer. The parts that were changed are not interchangeable with the previous type synchro. The ID mark on transmissions having the pin-type synchro,  will be a 4-leaf clover stamped on the date and model number pad of the transmission case cover face."

Edited by keithb7
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**M-5 .. 1946 to 1948 Chrysler/DeSoto

**M-6 Group one 1949 to early 1950

Chrysler/DeSoto and Dodge

**M-6 Group two Late 1950-1953 non Fluid Torque Drive..Chrysler-DeSoto and Dodge

**M-6 Group three 1951 to 1953 Fluid Torque Drive ...Chrysler and SOME DeSoto's...

So between M-5/M-6 transmissions..

The  cases and rear extension housings are different. 

Oil pumps are completely different..

Interrupter switches different..

Solenoids different ..

Multiple differences in the side covers..

Levers and BU switch options ..

1951 to 53 torque converter M-6 uses different gear ratio sets..

There are quite a few differences on these transmissions as they got updated from 1946 to the end in 1953.

There are a few more I cannot remember..

 

 

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FTD is a greatly improved performance transmission and fluid drive coupling...

The coupling is now a torque multiplication torque converter instead of a sluggish fluid drive coupling.

The new FTD M-6 transmission also uses new ratio gears for use with the torque converter.

FTD provides much better acceleration from a dead stop compared to the 1946-50 standard Fluid Drive coupling cars for sure!

Too bad the trans still has that two second lag in upshift.

 

Edited by Dodgeb4ya
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My ‘53 6 cyl Windsor has the FTD. Its adequate and drives pretty well in modern traffic. I’ve never driven a a non-torque fluid drive unfortunately. I can’t compare to offer differences. 
 

Yes, my FTD 6 cyl shares engine oil with the torque. A rare hen indeed. 

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I would never use the word "brisk"when describing acceleration from a stop with a fluid drive car. 

Now a Chrysler Hemi with a good FTD converter....acceleration is more than brisk....mash the pedal in 3rd and the bias play tires should make plenty of noise....... for 30 feet!

When a FTD converter fails the car will barely get out of it's own way and then then all the oil leakage issues.

I've never driven a Chrysler six cylinder torque converter car.

Hemi Chryslers...driven several and own one.

I have driven a couple Plymouth's with lethargic converters.

They were awful....would barely go up the slightest hill.

Both were converter failure cars.

 

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I think those Plymouth transmissions were called Hy Drives?  In the 46-51 M-5 and M-6 fluid drive transmissions, I've noticed a lot of drivers shift down to first at stop lights trying to get faster take offs, and then shift up where I guess they would be skipping 3rd and be in 4th.  This goes against Chrysler's recommendation to start in 3rd.  Do you think starting in 1st and then up shifting is a bad idea?  I think FTD torque drive cars require a 13 gallon oil change.  Is that correct?  I think Chrysler got the fully automatic Torque Flight in 1954?  Does Torque Flight still use the electric wiring harness like an M-6 with a governor and solenoid?  Or does it work without electric parts?  

 

 

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In my experience with my Windsor, 1st is bull -low and of little use. I don't see the point in trying to increase acceleration speed, by starting in 1st then lifting the gas pedal to shift to 2nd. Then clutching in to shift to high range 4th. When you do this, 3rd is skipped by design. 3rd is only accessed by mashing the gas pedal when in 4th, forcing a down shift. Or slowing down, idling to a stop, it will auto down-shift to 3rd. 13 quarts of engine oil in my 6 cyl FTD. I don't believe larger V8 FTD did not share engine oil with the torque. They had a torque sump oil pan at the bottom of the torque, and an oil cooler up by the front left of the engine.

 

2nd and 4th gear offer engine dynamic braking. 1st and 3rd do not.  This is due to a sprag-type over running gear that meshes with the tranny input pinion.  I select low range, 2nd gear to slowly go down my local steep hill whenever I go out for a drive. Single reservoir master cylinder means you need a contingency plan!

Edited by keithb7
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I always take off in 3rdin my M-5/M-6 Chryslers.

..no acceleration problem...as long as your not trying to race a Tercel off the line.

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Then you're doing it right for a change!  Now I want to hear from the guys who own a pre-war Vacamatic semi-auto transmission.  Do they drive about the same as the post war M-5's except for using engine vacuum for the upshift?  

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Those M-4  Vacamatics/Simplimatics shift just the same as a M-5/M-6 transmissions and work great.

There is an early and a late M-4 

Early is a vacuum operated diaphram shifter...the rubber diaphram tended to fail somewhat prematurely so.....

Then came the late style which is a piston type...also vacuum operated direct speed operated shifter.

Electrical systems are different between the two.

A lockout cable was also used on the

M-4 transmissions to enable tow starting the car.

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Funny, I've been around pre-war Chryslers and DeSotos, but I've never driven or ridden in one!  The oldest car I've ever driven personally was a 41 Plymouth coupe.  It was just a test drive though.  Now that I'm getting my 48 DeSoto ready to start, I'm wondering about my clutch and my transmission.  The new clutch was put in some 35 years ago and has been engaged all this time.  I'm thinking of removing the clutch and checking the flywheel just to see that it hasn't rusted in place.  The transmission always worked fine, so I haven't done anything to it except that I'm going to install a new wiring harness.  Other than drain the oil and refill it, and reconnect the shift levers, I guess there's nothing else to do to it before starting the car for the first time?  

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As for the FD coupling fluid I'd say just check the fluid level only. Don't attempt a drain and refill.  The Bellows seal and graphite ring might not like it.

Do drain and refill the transmission.

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Definitely check it....at bell housing hole.

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