Question on Overdrive

[steveplym]

I've been thinking about adding an overdrive to my car. Would make it much nicer to drive on the highway. How much would I be expecting to spend? Where is a good place to find a trans? What kind of modifications if any would I have to do to do the swap on the '47?

Will everything work since I went to 12 volt?

Thanks for any help you give. I'm just looking for input for my next endeavor.

[BobT-47P15]

Steve, I believe the solenoid on the overdrive would need to be 12 volts also.

Maybe you could happen onto a trans from a 56 or 57 model Plym.....whichever

year they went to 12V.

George Asche is the guru of overdrives.

His phone number is found in numerous previous posts, and probably in the

reference section as well. They say if you call him, be prepared to chat a

while.

[Normspeed]

The overdrive trans is the same length as your P15 3 speed, so it should not need any driveshaft mods. You will need a longer speedometer cable because the OD has the drive gear in a different location. You'll need the complete trans with OD because there are internal differences in the trans case with the OD unit. The emergency brake drum is also specific to the OD trans, your P15 3 speed drum won't work. You'll want to try and get the complete setup including the kickdown switch, OD wiring harness, dash handle and relay. Not sure on the 12 volt question but someone here will know.

I love my OD, it makes a world of difference on the highway. I've seen them sell (used) for $1,000 to $1500, and then again I've seen entire cars with an OD sell for $300. Depends on how lucky (and patient) you are.

[greg g]

Why not just update the rear end, to something modern with a 3.55 or 3.23 gear set.

Mopar B bodies, jeep cherokee, and ford all have the same bolt pattern and gears along those lines.

[blueskies]

I have about $750 into my overdrive.

I bought it from a junk yard for $300, and rebuilt it myself. I had never opened up a transmission before, and it wasn't all that hard.

The money I have into the overdrive includes a new 12v solenoid, new 12v relay, NOS cable, NOS input pinion shaft, Ebrake lining, and a rebuild kit that contained all the seals and bearings.

Worth every penny, IMHO. Without the overdrive, my car would be just a parade car. Instead, with the overdrive, it is a globe trotter that I would drive anywhere.

Pete

[James_Douglas]

Mine now works fine. However, I purchased a "rebuilt" unit outright from George Asche for more than $1500 and ended up having to tear the thing apart myself and replace the many parts that were NOT within specifications of the factory service manual. I also had to pull case gallery plugs that were not removed and clean galleries for the shifter rail interlock plug among other things.

I would recommend that you find a core and rebuild the transmission and overdrive yourself or act as "general contractor" and look over the shoulder of a willing local shop.

Once in the car it makes it very drivable as evidenced by the long trips people on this forum have taken with this set up.

Best, James

[steveplym]

Thanks for the input guys. I'm not sure what I'm going to do yet. I've got a friend who will help me with it, but it will have to be later in the year. Just thinking out loud I guess.

I'll probably call George Asche at the least. Like you said though Bob from what I hear I better be ready to talk a while.

[msawdey44]

One note on the solenoid issue: if you have converted to 12 volts, yes, you do need to locate a 12 volt solenoid. The solenoid actually contains two coils, a "pull in" coil and a "hold in" coil. They have different resistance values and thus cannot be operated through a single voltage dropper. The '56 transmission is the same as the earlier ones (the "selector" type) and that year was 12 volt. From '57 onward, the transmission design changes, though I don't know whether this also affects the overdrive unit. I agree that an overdrive unit makes the old Mopars much more driveable--back in the '60s I put one in my '51 Plymouth and drove all over the country.

[hkestes41]

I drove my 12V converted car for about 8 months after I installed the OD with a 6V solenoid. I had some wiring issues and changed to a 12V solenoid during resolution of the wiring issues.

Bench tested the 6V solenoid after I had the wiring issue resolved and it still worked fine. I then sold it on Ebay and the purchaser informed me it worked well when he installed it in his car.

There are threads on the HAMB discussing this issue and several guys say they have been running 6V solenoids on 12V systems for quite some time.

So, I would say if you can find a 12V soleniod for the right price buy it. If not then run the 6V until you come across the right deal on a 12V unit.

[55 Fargo]

Why not just update the rear end, to something modern with a 3.55 or 3.23 gear set.

Mopar B bodies, jeep cherokee, and ford all have the same bolt pattern and gears along those lines.

I like this idea Greg, I have a 3.73 in my 47 Coupe, would be will to try a 3.55 diff when I can find one, as Chryslers with fluid drives and M6 trans came with 3.55 diffs, not sure how a 3.23 diff would work with these cars.

I have plenty enough jam to take off with a 3.73 rear end in my heavier then P15 Chrysler, but would this work well witha 3.23, not sure.

I live in flat country it would probably be okay, but maybe not in hill country.

Does anyone on here have a Dodge or Plymouth witha 3.23 rearend running with a flat head 6 and 3 spd trans, would like to know how it is....Fred

[Jerry Roberts]

[quote name=Rockwood;... < snip > I live in flat country it would probably be okay' date=' but maybe not in hill country.

Does anyone on here have a Dodge or Plymouth witha 3.23 rearend running with a flat head 6 and 3 spd trans, would like to know how it is....Fred[/quote]

Fred , I live in flat country too . My 1941 Plymouth truck has a 3 speed and the 218 motor . My rear end gears are 2.94 from a Dakota and they work great here . Earlier this week I took a trip up into the mountains and on the long up hill pulls I had to shift down to 2nd gear . Like the big rigs , I was going real slow near the tops of the peaks .

[55 Fargo]

Fred , I live in flat country too . My 1941 Plymouth truck has a 3 speed and the 218 motor . My rear end gears are 2.94 from a Dakota and they work great here . Earlier this week I took a trip up into the mountains and on the long up hill pulls I had to shift down to 2nd gear . Like the big rigs , I was going real slow near the tops of the peaks .

Hey Jerry, that is good to know, wonder if I could bolt in the same type of diff on my 47 Chrysler coupe, my car weighs about 3600 lbs, how about your truck, how much would it weigh?

[greg g]

I think that the fluid drive would make up for any differences at take off. Maybe a little less quick but the good thing about the fluid coupling is it other tha speed won't care what gears are in the rear end except as noted on long hills. Guess one of the few advatages to the 4.11's I have is it will accelerate while climbing highway grades.

[55 Fargo]

I think that the fluid drive would make up for any differences at take off. Maybe a little less quick but the good thing about the fluid coupling is it other tha speed won't care what gears are in the rear end except as noted on long hills. Guess one of the few advatages to the 4.11's I have is it will accelerate while climbing highway grades.

Yes fluid drive would be advantageous off the line with higher rgear ratios, but for me I have a dry clutch in my Royal Coupe......