plyroadking

I didn't realize he did either. A little further down should be the date stamp. Here's a picture of what one of them on the bench is stamped, 4-1-55

Overdrive transmission cases and standard 3 speed transmission cases are different, you most likely have a transmission case that came with an overdrive. If you look in the area I've circled you should find the date stamp of your transmission. I presume the whole "don't back up with the cable pushed in" paranoia stems from the model A community that put r10 overdrive units in their torque tubes and have no other provisions to prevent damaging the unit while backing up. When used with the proper transmission case, there is a rod that disengages the overdrive when you shift the transmission into reverse gear.

I had a noisy overdrive once, turned out to be a combination of the parking brake drum nut was loose and excessively worn rear bearing, probably caused from the loose nut. It would allow the annulus to rub/grind on the case. Studebaker switches will work part number 529479, also cole hersee made/makes them, part number 9106-02. You can order/buy a new kickdown switch for a '49 Mercury at most parts houses. They are about twice the size of the "correct" switch but if you're going to custom mount it somewhere non-factory they will work. We've been running 90's ford explorer fuel pump cube relays for years to operate our overdrives. 6v seems to energize the coil without any issues, but I still have a spare in the glove box.

After ~70k miles, probably about 7-8 years, of running a modern 75W-90 gear lube in mine I decided to pull it apart, clean it, and try the gl-1. (I had it apart several times when I first got it and I had cleaned it well) its also has the pre 1955 brass syncros. I couldn't find any signs of deterioration on the brass or on the thrust washers that are supposed to be susceptible to the modern lube. I slapped it all together and filled it with the gl-1, first trip out the door and it shifted terribly, I had to pause between the gears and shift very slowly or it'd grind while I shifted. I figured the lube was just cold but it didn't improve once it was hot. I gave it a couple weeks then drained and refilled it with the 75W-90. It shifted just like I was used to before I tried the gl-1. Its pushing 90k miles now and still shifts great. One person I sold an od trans to specified using the gl-1 for my after assembly test drive, it also shifted like a 100 year old truck transmission. If someone wants to try it, I've got a mostly full 5 gallon bucket of gl-1 that I keep tripping over in the shed.

Here's a planetary gear set I found in one of my overdrives, not sure what the previous owner did to make it occur. Took half a day of gentle prying to get the overdrive disassembled. I robbed everything out of a $40 ford overdrive transmission to repair it, that was probably 55,000-60,000 miles ago and it's giving me no issues. I'm more than happy to pull a ford unit apart and send parts for your mechanic to put in your case. I've also got good used transmission gears all over the garage, I do not want to get rid of the shafts though.

Did you get pictures of the parts that need replaced? If its just the overdrive or trans guts then you're in luck. The only "critical" parts are the cases, main shaft, and output shaft. Everything else is "cheap" to replace, the trans gears all interchange with standard 1940-1955 Plymouth transmission parts, and most all the overdrive parts interchange with "cheaper" ford/gm r10 overdrive units. I've got a stack of them that are my source for od parts anytime I open up a mopar unit that needs something replaced.

Just a matter of slapping the fluid drive input shaft from your transmission into the overdrive transmission. And then rigging up a kickdown switch on your throttle. Also need to make sure the overdrive is a pre 1955 as I believe it was '55 when they changed to the pin type syncros or you'll also have to swap your gears in the trans as well. Now the England part might make overdrives a little harder to find.

Where are you located?

I don't think they'd fit nicely on a standard tranny jack. I just jack the car up fairly high and then slide them out or in while laying on my back.

They're pretty easy to rebuild/repair depending on which one you have. Could either be an R7 or a R10. If its an R10 then it's easy and cheaper. The R10 was used by chevy, ford, studebaker, hudson, etc. However the cases and shafts are different but most internals will interchange. Rolling them in reverse with the overdrive cable shoved in can upset the spragg clutch. They have a lockout rod that temporarily "disengages" overdrive when shifted into reverse.

You've also got to check the other 1934-'55 mopars in the yards as well. They've been a popular transplant in non originally equipped cars for awhile. I removed one from a '48 Dodge and a '41 Plymouth that I found in salvage yards.

Hard to tell but looks like it has 16 count spline for the axle shafts. I'm not sure when they changed from 10 spline but that 3rd won't just slap into at least a 1940 though 53 Plymouth.

Most of the internal R10 overdrive parts will interchange with R10s that were used on other makes. However the cases, input, and output shafts are make specific. The governor drive gear does not interchange and the solenoids are different once you get away from borg's overdrives made for the big three. The Packard you have most likely won't bolt into your car, the input shaft is different for one and also no provisions for the parking brake either. I presume with enough ingenuity and machine work it could be made to fit though. I'd recommend finding a 1952-1955 Plymouth transmission with overdrive as it'll bolt right in and no serious modifications are required.

In order to achieve the final drive ratio an overdrive provides you'd have make a big drop in a rear end ratio. One ratio calculator i like is http://www.public.asu.edu/~grover/willys/speed.html#:~:text=Engine RPM divided by total,gives vehicle's speed of travel. It allows you to put in an overdrive ratio and play around, R10s are a 0.7 I swapped out my 3.9 ratio 3rd member to one from a 50s dodge that's 3.73. That only gave me a 3mph speed increase. In my opinion adding an overdrive is the less intrusive and easily reversible route to go. I've logged around 80k miles with my '40 that has an overdrive in it. I used to live in the Sierra Nevadas and used 2 gear with overdrive many times climbing the hills, when I lived in the bay area it was really nice to be able to keep up with everyone else doing 80mph in the 55 zones. Now that I'm in Iowa, I'm considering swapping in my 3.54 ratio 3rd member for crossing the plains. Overdrives can be expensive if you just want to pay for one to show up on your doorstep. I've collected and sold many of them, I usually had to buy the entire car just for the transmission. They're very well built and just about every used I've torn down was in a condition that I could have just changed the fluid and slapped in the car.

I've been pretty happy with the b&b except for the excessive wear on the butterfly shaft and housings after 80 years. They're simple to rebuild and seem to be a set and forget carb. I stumbled upon a '55 dodge factory 2 barrel intake and carb several years ago. More carb means more hp right!? So I slapped it on my '55 ply 230 in my '40 Plymouth. I didn't notice enough difference to write home about except that it'd finally idle at a really low rpm because I wasn't sucking air in around my worn out butterfly shaft. I found a nos '40s b&b a couple years ago and will swap it and manifold back on next time I'm feeling ambitious.