Why no 46-48 Chrysler OD?

[wagoneer]

I've read the history of OD, and other posts on here, HAMB, elsewhere. There is a conspicuous gap between pre-war and 1952 where the fluid drive Chryslers have no overdrive gears. Chrysler clearly had the technology, but did not add an OD gear? Maybe because of the "automatic" upshifting?  They did it later on, but there doesn't seem to be a satisfactory explanation as to why the high end Desoto/Chryslers were left out of the OD in post-war years?

 

I only lament because these engines are so big, and capable, and would be very suitable for high cruising at 75/80 mph along with the rest of traffic, but really suffer from running out of gears to support the highway cruising speeds. 

 

Any solutions for 46-48 Fluid drives ?

[chrysler1941]

Very interesting subject. Don't know the answer.

My spare part list and workshop manual has many pages regarding the M4 Vacamatic over drive unit fitting the C-28, C-30 and C-33. What model is yours?

To my knowledge the M4,5,6 has same bolt pattern for the tail shaft so theoretically they should fit. 

I have downloaded this photo (probably from this site) showing M5 with overdrive stated as R7.

But where do you find those OD ? Is it a R4? R5-10 ? Maybe others know more.

I'm prepared to help you with documentation as I'm also interested in an OD.

[Dodgeb4ya]

The above trans was sold on ebay several years ago.

That trans is an odd ball for sure.

It is an M6...1949 and later.

As for no OD's used on the 1946-48 Chrysler's?

My guess is the M5 trans with a OD added on probably have been too costly, also too long to fit in the convertible "X" member cars, and maybe they thought they wanted to do away with the mid to late 30's era of Chrysler overdrives....simplify higher speed operation of the "New" 1946-48 Chrysler.

This being accomplished with high speed rear end gear ratio's.

Windsor's 3.54

Saratoga, New Yorker 3.36

Crown Imperial 3.58

All just a guess.

.....I know especially the eight cylinder cars easily drive 70 smoothly and quietly all day long.

The six cylinder Chrysler cars have no issue at 60...though there is some fan noise...not nearly as much as say a Plymouth or Dodge with lower ratio rear ends.

Edited April 5, 2021 by Dodgeb4ya
Wrong word

[chrysler1941]

So basically you mean any MoPar OD will fit any MoPar transmission?

[Dodgeb4ya]

No not at all.

The OD transmission front cases are unique having extra machine work done to them.

There are extra oiling holes and shift rail holes needed to adapt an OD to a transmission.

The old 30's overdrives are big,heavy and complicated transmissions.

Lucky me today I finish putting one R9 in a 41 Packard 180.

[chrysler1941]

Ok I'm trying to learn about OD. So this photo shows the 41 model. Is this the old one you mean?

I see guys here talk about R numbers. Is this a MoPar thing or ?

What R umber will this be and how many R numbers are there? Which model is most sought after?

[wagoneer]

8 hours ago, Dodgeb4ya said:

The above trans was sold on ebay several years ago.

That trans is an odd ball for sure.

It is an M6...1949 and later.

As for no OD's used on the 1946-48 Chrysler's?

My guess is the M5 trans with a OD added on probably have been too costly, also too long to fit in the convertible "X" member cars, and maybe they thought they wanted to do away with the mid to late 30's era of Chrysler overdrives....simplify higher speed operation of the "New" 1946-48 Chrysler.

This being accomplished with high speed rear end gear ratio's.

Windsor's 3.54

Saratoga, New Yorker 3.36

Crown Imperial 3.58

All just a guess.

.....I know especially the eight cylinder cars easily drive 70 smoothly and quietly all day long.

The six cylinder Chrysler cars have no issue at 60...though there is some fan noise...not nearly as much as say a Plymouth or Dodge with lower ratio rear ends.

 

I drive my Windsor on the highway about 60-65mph max at the moment. I have never floored it to see how fast it would go. It *should* make it to 70 easily but what I will leave behind on the highway.... I don't know. 

 

 

It's a bit loud at that road speed though comfortable. Anybody driving their 6 at 70-75?  My car doesn't yell at me when I slow down or make funny noises, but I'm still hesitant to bury it.

 

 

@Dodgeb4ya Would a hypothetical rear-end gear swap to 3.36 in my 6 resolve my problem in a simpler manner? 80 mph at 3300 RPM... According to this corvette thread on just such a topic. I should get lower RPMs but higher top speed . These guys are in a similar boat as we are with their older C3/C4. 

 

Could we... take it all the way down to 2.87 like these? there was some talk about this a few years back too.

 

Edited April 5, 2021 by wagoneer

[wagoneer]

you ask, and the internet delivers. I'm pretty somebody will sell the differential gears out of their m5/m6 transmission. Redline is 3800, so staying on the low end of 3000s at 75 is not too bad though being closer to 2500 would be quiet and comfortable. 

 

https://www.allpar.com/threads/the-chrysler-plymouth-dodge-desoto-fluid-drive.229898/

Quote

 

There are four forward gear ratios:
 

1. Underdrive Low: 3.57 to 1.00
2. Low: 2.14 to 1.00
3. Underdrive High: 1.75 to 1.00
4. High (Direct Drive) 1.00 to 1.00

 

 

http://chevellestuff.net/tools/rpm_calculator.htm

 

 

 

 

Swap out the rear-end, add an OD, and you could be cruising at 85mph at 2500 rpms

 

[Dodgeb4ya]

85 in a stock suspension old Chrysler....naw.

M5/M6 gears are not gonna get ya going faster.

Only way is a different rear end.

The straight 8 3.36 rear end will not fit the six cylinder cars...much bigger in everyway .

[MarcDeSoto]

Also, if you go to too low of a rear end ratio, wouldn't it be a real slug trying to start from a stop with the non torque converter Fluid Drive?  I know my 48 DeSoto cruised the freeways just fine that way it is with a 3.73 differential.  I didn't cruise at more that about 60, but if I wanted to cruise at 75 to 80 and get tickets, there's an easy solution.  Drive your modern car!  

[wagoneer]

I'm just hoping for 70/75 to keep up with traffic. I like to think of my Chrysler as a daily-driver, and something comfortable to go around in.  Hard to avoid highways, and engine noise above 60 starts intruding into the cabin unnecessarily (on my list to add sound deadening material). 

 

The Windsor suspension is oddly not too different from my old Grand Wagoneer - but the ride is better.

 

It's a 4.1 liter engine with a ton of low-end torque; I think it could handle some higher gears. 

 

People want to throw in Hemis and small-blocks into these cars for "performance" but I think that misses the point. 

 

I'm under no illusion of beating the corvettes or even the CR-Vs. I want a nice town car that can go on trips too. You know... what people did with it when it was new. 

 

I'm pretty sure somewhere some company is making replacement differential gears for our beloved Mopar differentials. 

 

Next year, I plan to  run the car in the great race with my son. 

[greg g]

Well Chrysler's had taller tires, a slightly better rear gears. 3.8s to1 instead of 4.11 like in my Plymouth.  As such their rpm at 60 was less than the lesser cars. Running the numbers with a 1 to1 top gear 29.3 inch diameter tires (8.25 15) 3.8 rear gear yields 2600 rpm at 60.  My car without Od is at 3250, with OD is apx 2450.

 

So the folks in engineering probably the OD would have dropped the rpm too low,. Would be around 1800 at 60.

[wagoneer]

Found this great quote from @James_Douglas  -- 

 

https://p15-d24.com/topic/40078-of-mopar-flathead-reliability/page/4/?tab=comments#comment-424881

 > I removed the M5 trans and keeping the fluid coupling and added the 3-speed with Borg-Warner OD.  

What's exciting is how James Douglas uses his for long distance trips, and has great reliability.

 

Also from @55 Fargo with the Chrysler 8 1/4 diff that has the  3.23 rear end. His trans has even higher gearing than the M5, but his videos show nice smooth power.

 

https://p15-d24.com/blogs/entry/125-a833-overdrive-trans-conversion/?tab=comments#comment-722

 

Seems Both an OD and low rear diff gearing is possible just need to either swap the trans that has the OD already, swap the rear differential, or find substitute gears somewhere for rear diff

@James_Douglas Do you have any more info on your 3-speed OD swap coupled to the fluid drive? Which specific trans did you swap in? Do you know what it came from, and did you have to mod your suburban shift linkage from column to floor shift?

 

[James_Douglas]

My first OD trans for the '47 Desoto I purchased from George Asche. I would not use him again.

 

After I took apart the transmission and replaced all the parts that were worn beyond specifications, and made sure the inside of the case in all it little nooks and crannies were actually cleaned of gunk, it has worked great for 15 or more years.

 

I also have a spare.

 

What I found is that a LOT of the internal parts on these are worn to the point where they will work, but how well over time if driven a lot is an open question.  These are not hard to rebuild as long as you get all the books (I have them electronically) and take your time. If a part looks worn or measures out worn then replace it. Sure you will spend a couple of months and about $2K to $4k in parts by the time you are done, but you end up with a basically as new transmission that will live a lifetime if you keep the oil changed.

 

Do not pay more than $500 to $700 for a core no matter what the seller tells you. Unless he has photos and receipts for internal replacement parts. Like I said in the opening, I learned the hard way.

 

Once you source one from a 1946 to late 1950's MOPAR the things that make it work on a Fluid Drive Chrysler or Desoto are as follows:

 

1. You need the input shaft from a fluid drive 3-speed transmission not a M5/M6 Semi-auto transmission.
2. You will need to double check the output housing to get one that can take the BAND and not the drum style parking brake.
3. You will of course need the electronic parts. The booklets go over that well.

4. You will have to cut the drive shaft for the difference in length.

 

A couple of specific points. The second gear comes in two versions. For a lighter car the so-called fast second gear is not a bad choice. For a heavy car however, use the regular second gear. I would also use the regular second gear when using a fluid coupling. You can go find my threads on that.

 

The Borg-Warner OD main shaft is very hard to find NOS. The problem is that the second gear rides on the shaft and the back end of it "pushes" against a step on the shaft.  That is at the flutes. What happens is the shaft wears. I had a situation were even with an NOS second gear and the largest snap ring there was still too much end play to be within the specifications.  What I did was take this NOS second gear to an Industrial hard chrome shop. They build up the back thrust side of the second gear to my specifications. When done the second gear end play was at the very bottom of the specification range.  The second gear has been VERY quiet for 15 years.

 

Just this last year I found a NOS 3-speed (BW) main-shaft. It cost me a couple of hundred but that is the same I had to pay to plate the second gear. I am going to be rebuilding my spare to as new condition and crating it. If I ever have a problem on cross country retirement trips...it will be ready to go.

 

James.

 

 

 

 

 

[chrysler1941]

Thank you for your detailed explanation. I must admit I'm more confused now ?

I have been staring at your photo for a while and it looks like a manual transmission ?

I can see the overdrive on the left, it looks like the model 282/283 pictured in my book, but if's almost as big as transmission case, and will require a shorter propeller shaft ? 

My transmission has no tail shaft, just the a narrow holder for the brake.

Has this OD anything to do with ODs with R numbers?

 

 

[wagoneer]

@James_Douglas I keep staring at the picture trying to mentally put the parts together along with your description.

 

 

Let me repeat to you what I think you did for my own clarity: 

 

    You took a standard 3 speed gearbox from 46-50 probably from dodge or Plymouth, modified it with an assortment of parts including an input shaft from a mystery manual fluid drive trans (post 48?) that is long enough to fit the BW overdrive (from what year?) and then modified your drive shaft to accommodate the extra length thereby creating a one-off (now two) post war overdrive enabled  fluid drive desoto . The difference between your 3 speed and our 4 speed semi automatic is the automatic upshift/Downshift provided by nominal fluid drive vehicles !

 

in the words  of Doc McFly,  Great Scotts!

 

 

 

[chrysler1941]

1 hour ago, wagoneer said:

@James_Douglas I keep staring at the picture trying to mentally put the parts together along with your description.

 

 

Let me repeat to you what I think you did for my own clarity: 

 

    You took a standard 3 speed gearbox from 46-50 probably from dodge or Plymouth, modified it with an assortment of parts including an input shaft from a mystery manual fluid drive trans (post 48?) that is long enough to fit the BW overdrive (from what year?) and then modified your drive shaft to accommodate the extra length thereby creating a one-off (now two) post war overdrive enabled  fluid drive desoto . The difference between your 3 speed and our 4 speed semi automatic is the automatic upshift/Downshift provided by nominal fluid drive vehicles !

 

in the words  of Doc McFly,  Great Scotts!

 

 

 

Oh ......is that what he meant....?

[James_Douglas]

Oh...a photo is worth a thousand words. That is a M5/M6 Semi-Automatic. There is no Borg Warner overdrive for that unit.  You could go to a modern Gear Venders overdive, but be prepared to spend about $4K to $6K to do that by the time it is all done.

 

Go find a three speed stick with the overdrive on it and rebuild it with the fluid coupling input shaft. I use my in San Francisco traffic all day long and leave it in 2nd gear and just use the OD in second.  On the highway up to my place out of town, I run at 56-70 all day long in third overdrive.

 

James

[Dodgeb4ya]

Get a straight eight 46-48 Chrysler...no need for OD.

cruises fine at 70.

[chrysler1941]

Get a three speed with overdrive, get a straight 8.....not happening where I live. ?

 

 

 

[Dodge City]

Has any body ever tried or had experience with the modern Gear Vendors overdrives?

Their website states they make a bolt on for every classic car imaginable. They have a great reputation in the racing community.

Just mounts behind your existing transmission, either automatic or manual with a simple switch on dash to engage or disengage or use a dimmer type switch on floor if you like. You would have to shorten the driveline however.

The website show price at $2850. Spendy but a simple solution...

[greg g]

Gear vendors bought the rights to manufacture their overdrives from Laycock de Normanville.  These are self contained planetary gear boxes that were used by various brands of vehicles made in Europe.  Jaguar, Austin Healey, Volvo ,MG were some who featured these. A bunch were sold over here and now may reside in junkyards. I had a late 80s Volvo 960 station wagon with this over drive behind their four speed.  It waswired to engage with a button on the shifter.  I don't know if it worked as it came from the factory, but mine would only engage in fourth gear.  You let off the gas, pushed the button and it engaged.  If you moved the shifter out of 4th it would disengage.  It didn't seem to have a kickdown function for passing or going up grades.  If you needed to drop out of OD, you let up on the gas and flipped the switch.  So the system could have been messed with some where during its 170000 before I got it.  It would not engage on any gear but fourth, but it seems to me that it could be wired to be switched in any gear to allow split shifting of the intermediate gears as well.  Perhaps there was a position switch that only allowed the solenoid to be powered in top gear.  But some shopping around some wrecking yards might yield up the similar unit.  A friend got on for his Jaguar sedan a few years back for a couple hundred bucks.  He needed to fab up some mounts and modify the drive shaft but when installed it operated fine. Not familiar with the wiring but I know there was a relay on mine in the wiring under the counsol,and a Russian the slot that was number Ed as overdrive.

[chrysler1941]

No your Volvo was working correct. My dad's Volvo was the same. Although I never let of the gas when pressing the OD button.

I actually have one of these OD lying around. but I'm not going to use it it. Not messing with my propeller shaft. ☺️

Edited April 20, 2021 by chrysler1941

[Dodge City]

Greg G, I appreciate the clarification on how one works. The factory OEM overdrive's on Ebay listed for $1800 and possibly have to spend a few more thousand to get them rebuilt when getting them, this just seemed like a fair alternative to the increased speed issue so many are trying to figure out. Sure seems like the cheap way to go is a ring and pinion swap of the rear end gears for around $200 will work better for those on a budget...

[chrysler1941]

7 minutes ago, Dodge City said:

Greg G, I appreciate the clarification on how one works. The factory OEM overdrive's on Ebay listed for $1800 and possibly have to spend a few more thousand to get them rebuilt when getting them, this just seemed like a fair alternative to the increased speed issue so many are trying to figure out. Sure seems like the cheap way to go is a ring and pinion swap of the rear end gears for around $200 will work better for those on a budget...

These pumpkins are different. As far as I know, no one makes parts for them.