'53 DeSoto Tip Toe Shift Transmission Issue

[AlamedaDave]

I have a '53 DeSoto (S16) with the 276 V8 and Fluid Drive (aka... Tip Toe Shift). I've had the car for a few years, all has been working great and up until recently was the poster child for how the Fluid Drive should work. 

 

Over the course of the last two drives in the car, the car would move from 4th to 3rd gear unexpectedly around 50-55 MPH and cause either the engine to go into high revs (slip to 3rd) 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.

 

I checked… oil level is good. 

 

After some research, today I swapped out the solenoid.  This was admittingly kinda a lazy move without other troubleshooting but was also convenient as I had an extra solenoid already.  But alas… this hope for a quick fix didn’t take hold. 

 

So, here is a more complete description of the behavior after the 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 and steady speed 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. 

 

I am not very mechanical and this one is way over my head.  My mechanic is setting aside time to look at this 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, the input I hope to receive here, and his 35 yrs of experience (but very little with this transmission). 

 

Any suggestions as to the issue? Thanks much... Dave

 

[Dodgeb4ya]

Did you look at the governor contact points for oil contamination? Don't file them... carefully clean with contact cleaner...

Here is a video on trouble shooting your M-6 transmission            . http://www.mymopar.com/index.php?pid=382

 

I usually quick test the transmission if it won't up-shift by removing the solenoid wires  and do a quick road test to see if the trans will quickly up-shift and stay in direct high.

That proves the oil pump and hydraulic shifting parts are OK.

The car will not downshift quickly with the power shut off from the solenoid so this is just a quick test to see if it will up-shift quick and stay in direct high. Push the clutch in at a stop to cause a complete downshift at a stop with the wiring dis-connected or when backing up.

If this test does make it up-shift OK with the wiring disconnected it means the issue is electrical, wiring, kick down sw. in the carb, governor etc... nothing wrong inside the transmission.

[Doug&Deb]

The Imperial website has a troubleshooting manual available for download. I’m a bad mechanic but I was able to follow it easily. One other thing to check, on the right side of the trans between the drain and fill plugs is another plug. Remove it and check that the bolt for the shift fork is tight. I believe you’ll need a 7/16 deep well socket. The m-6 is usually pretty bulletproof so it’s probably something minor. My problem was some bad wiring. Once I replaced it I’ve had no problems. Good luck.

[MarcDeSoto]

Have you checked the oil level in the transmission.  I had similar problems and saw that my oil level was almost empty!!!  The drain cock was loose and dripping! 

[James_Douglas]

Based on my experience, I would say the problem is the Direct Speed Clutch, the ring that goes with it and probably the input shaft. What happens is they wear out and then you get the problems you are talking about.

 

Attached is a photo of the clutch and its ring. One this that is important to tell your mechanic.  He MUST mark the clutch before taking it apart or it will go back together, but not work. It is NOT in most of the manuals and people miss it all the time. The index marks are either worn away or they are not there.  I have had NOS parts without the mark. I have, before I knew, put a trans back together and it did not work for reasons unknown at the time. Once I lined the part up it worked just fine.

 

By the way, finding a new clutch is VERY hard. The last one I got was from Frank Mitchel and it cost me something like $250 and that was the last one he had.  For a friend, took one and dressed all of those edges very carefully. You can see how banged up there are in the photo.  I then sourced a new ring and a new input shaft and it solved his problem but it is problematical trying to dress and old part. 

 

Good luck and let me know what ends up being the problem.  Also, note that the V8 cars with fluid torque drive cars, have a transmission that is different that the fluid-drive cars. They made gear and other internal changes.

 

[Dodgeb4ya]

On these M5/M6 hydraulically operated transmissions... once they start banging/popping out of auto up-shift high gear can be damaged very quickly.

This meaning rounded off teeth on the input shaft, direct speed clutch sleeve and blocker ring. 

To do the repairs to fix this for the nest 20 years all three pieces mentioned above must be replaced to prevent popping out of gear on steep inclines.

And the transmission transmission oil pump oil pressure needs to be around 40lbs or higher.

All three pieces are now extremely hard to find and if found probably very costly as James mentioned...

[MarcDeSoto]

excellent information about clutch sleeves gentlemen!  Thanks, Marc.  By the way, several years ago I sent the Imperial club my rare Master Tech filmstrip of the M-5 transmission, How it works and Troubleshooting called Special Kit A and A1.  It is similar to the one on the M-6 transmission for 1949 and later Chrysler, DeSoto, and Dodge semi automatics.  Here is a link:

https://www.youtube.com/watch?v=CuQzVraslzw&t=305s

[MarcDeSoto]

Quote

 

 

[James_Douglas]

The one thing to note on the indexing...it will go together and look fine even though it is in the wrong place.  That is why it is very important to market it BEFORE you take it apart or it can bite you in the butt. 

[AlamedaDave]

Thanks All:  Will keep everyone posted.  Additional efforts will begin tomorrow.  Hoping for an electrical/dirty contact/similar problem being at issue given the comments here about gear availability and potential costs.  Just in case I will seed the question:  Any potential lead sources for these parts?  

 

Dave

 

[kencombs]

I often see complete trans on eBay.  That would probably be cheaper than parts.

[James_Douglas]

Dave, The hard parts that wear are a bitch to find and when you do get ready for the price.  I have, and I am sure others do as well, ebay searches that will let me know immediately if one of those parts comes up. I have one so-so clutch and a couple of the brass sync rings. In my cars I have all new parts as to the clutch, ring, and input shaft.

 

Speaking of input shafts everyone, be warned....

 

For my '47 that has the fluid-coupling three speed and BW overdrive....

 

When we went to put the trans in it was the going in a little tough. As I was trying to suck it in the last inch and my 75 year old friend was warning me to not put to much tension on it...

 

at that moment I heard a pop and the case, by the ear I was working on, cracked. I know better, but I was tired and thought it was just a slight alignment issue with the pilot busing.

 

Well, after the dust settled down it turns out that the end of the NOS input shaft was 0.001 larger than it should have been. It would not go into the fluid coupling. As I remember it was supposed to dead on at one inch, but it was over just enough to not go.

 

Lucky in that I had a spare transmission, so I pulled the guts from the one and swapped it over to the other.  I also had a very good used extra input shaft (on the three speed it does not have the issues like M5/M6) and it has gone 40K without any issues. 

 

I wanted to warn everyone to double check their input shafts if they get an NOS one!

 

Some day I will weld up the old case and rebuild that three speed with BW overdrive to have a spare around.

 

James.

 

 

[keithb7]

Is there a way to line up the direct speed clutch gear with the main shaft, if it was taken apart and not index marked? What about times when you are swapping parts from one tranny to another for example? The parts going in are not what came out. What happens then? How do you line everything up right?

[Dodgeb4ya]

You don't have to mark them... but re-matching used blocker sleeve and input shafts is best advised as they wear in together.

On new parts or you cannot find match marks...

 

Be sure the splines of the third speed gear are indexed in the center of the group of three in direct speed clutch sleeve. When assembling the main-shaft into the transmission it will be necessary to rotate the drive pinion to obtain correct registering of the lugs on blocker ring with the slots in third and direct speed gear.

.005" is the backlash clearance when fitting third speed gear splines to the clutch sleeve.

Keep rotating the clutch sleeve around 3rd gear splines closest to .005" backlash.

Done.

Edited April 18, 2019 by Dodgeb4ya

[AlamedaDave]

Hi All, 

 

Part of this post is ego-suck and part of it is being OK with myself as never been raised around mechanical stuff and thus a contribution to my learning curve.  OK... that said:  I took to heart the advice of the input on this site and for that I'm big-time grateful.  I first watched the video that Dodgeb4ya (real name not known) included in his thread and then considered the post made by Marc.  It was then that I realized that while I was good about changing out the 12+ quarts of oil on the car - that these quarts only fed the engine and the fluid drive - and not the transmission itself.  So the first thing to check was the oil level in the tranny.  And, sure enough, the oil level was down about a quart.  I had always assumed (bad on me) that the minor oil leak under the car was from the engine proper.  Now I know this is not the case.  Upon filling the tranny back up with 10w oil to just under the plug, the car's test drive was just grand!  While we also checked all the connections while the car was on the lift, there is no doubt (in our minds at least) the oil level was the issue.  

 

Bottom line:  I'm thankful for the advice provided here and that I was able to use it to help direct the troubleshooting path I took with a generous mechanic who doesn't charge extra for me hanging out with him as he works.

 

Problem solved.  All good again, I'm now looking forward to have the car at the Silverado Car Show in Napa in a couple of weeks.  

 

Always humbled and thankful for what other's are generous to offer,

Dave

 

 

 

[keithb7]

On 4/14/2019 at 6:56 AM, James_Douglas said:

  Also, note that the V8 cars with fluid torque drive cars, have a transmission that is different that the fluid-drive cars. They made gear and other internal changes.

 

 

 

 

I have my OEM Moapr 1953-1954 Parts manual open here.  There are 3 different transmission options listed for 1953-1954.

1. Three Speed Manual

2. Presto-Matic with Pin Type Syncronizer

3. Power Flite

 

The "Presto-Matic", It appears, is the M6 tranny in this book.  According to the parts book, the optional Presto-Matic transmission assembly, part number 1408475, with Torque Converter is  shared with some the following 6 cylinder and 8 cylinder cars, within certain Serial Number ranges. 

 

S18 Desoto Powermaster 6 cylinder Canadian Built

S20 Desoto Powermaster 6 cylinder, USA Built

C60 Chyrsler Windsor Deluxe 6 cylinder, Canadian Built

C62 Chrysler Windsor Deluxe, 6 CYLINDER USA Built

D44 Coronet 8 Cylinder, Canadian Built

D50 Dodge Royal, 8 Cylinder, USA Built

D48 Dodge Coronet 8 Cylinder

D53 Dodge Royal 8 Cylinder

S16 Desoto Firedome, 8 Cylinder Canadian Built

S19 Desoto Firedome 8 Cylinder USA Built

 

The following 8 cylinder cars with the presto-matic M6 transmission option, has a different transmission part number 1324616.

Maybe these are different inside than the 1408475 above?  Reviewing the parts listings though, I don't see different part numbers

for individual parts used in these tranny's below, or above, listed here.

 

C56-2 New Yorker Deluxe Canadian Built

C63 New Yorker Deluxe USA built

C58 Imperial 

C64 *Unsure what model this is

C59 Crown Imperial

C66 *Unsure what model this is

Also noted: *Presto-Matic transmisisons were used up tp the following engine SN's: 

US Built  C58 4 door sedan. Town Sed. after C58-8-63900 also intermittently from C53-8-47701 to C53-8-63900 up to C53-8-50163.

 

...I think. The book has interesting layout. It is not the easiest data to get straight. Someday I may be forced to sort this all out. I have a spare C56 New Yorker tranny that I pulled

apart to learn its workings. I own a 1953 C60-2 Windsor Deluxe with the Presto-matic & torque converter. If I ever have tranny troubles and need spare parts, I'll be comparing

parts side by side.

[Dodgeb4ya]

The Chrysler Fluid Torque Drive M-6 trans has a different input shaft ( shorter and more splines) because of the new "Real" torque converter versus the std Fluid- Matic coupling

 

Also the FTD M-6 trans gear ratio's are different so as to match the increased torque into the M-6 compared to the old out dated Fluid Drive coupling...