Packard Forum Index » Pre-War (1899-1942)

As you know, my car is a ‘37 138CD. With it being a 138, it has the 4.54 rear end. I haven’t done it yet, but I will be installing 23rd series transmission with R11 OD. Well….I won’t be installing it, I’ll be having it installed.

I happened across it as Allen (who worked on my car in Wichita) happened to have it. He also had the governor, solenoid and speedometer cable. I was able to get the rest of the needed parts from Vintage Auto Garage. I was able to get a top plate from the Dallas office so that I can keep my existing transmission complete.

Once my car is out of the shop, I’ll probably drive it through the summer and then take it back to Allen late fall to have him install the OD for me. My understanding is that you have to modify the top plate, shorten the drive shaft and slightly notch the frame…then add the wiring etc..

I know my dad says he routinely drove the car at 70mph back when he bought it the early 60s. I’ve driven it short distances at 55 to 60 with no issues. But, like you, I want to drive my car a bit. I want to take longer trips such as KC to Chicago.

I used to drive my 1940 110 at freeway speed for distances too and never any issue but I finally installed an R9 unit. Unfortunately due to changing circumstances, I never drove it again after that but I expect it would have been a major improvement.

Ken, take HH56's learned advice. Scout up a junior 1948-on R-11 overdrive. They are more plentiful than 1940-early '48 R-9s, so less expensive, and slightly simplified (1939's single year R-6 was full mechanical, not as good. Hardly suggesting it was not good, so calm down any '39 OD owners.)

Even at a sedate and dangerously slow on today's freeways 50 mph, with overdrive, you're reducing rpm, saving gas, prolonging engine life, as you surely are at 60. You'll spend a lot of time at a relaxed 65-70 with overdrive, so long as traffic not dense and you remember that good drum brakes no match for today's ABS. Drum brakes like yours will stop you as fast, just not repeatedly as quickly descending long mountain grades as discs.

I had a '40 120 non-overdrive car with your 4.09 from 1974-83. Adding overdrive made it a super car, the best road car extant. Your '37 is on a smarter 120-inch wheelbase, and tho' we're talking about mechanics and drivability, Packard won the annual Gallup Poll's Most Beautiful Car three consecutive years 1935-37, their pontoon fendered '38 losing to Buick in '38. Packard never made a better car than the One Twenty, certainly not if drivability included. Seven inches less wheelbase than 1938-on makes for a different, more sporting road car, and floor shift is wonderful, simple. Packard wisely returned to 120 inches for their 1942-47 junior Clippers. Postwar Bentley Mark VI/R-Type, R-R Silver Dawn, and 1950-56 Jaguar Mark VII saloons did well with 120-inch wb.

Don't sell yourself short. Add overdrive. You can always shift down or kick out of overdrive, but it's a real drag to run out of gears.

Thanks for all the inputs. Certainly gives me a lot to consider! Whatever I do, I'll post about it in my project blog.

There's plenty of reasons to add one, but your statement alone: "I'll be moving to an area with lots of 45-55 mph country highways and no interstate".

Usually people ask about adding an OD when they are moving near an interstate, not away. Yes the car will drive a little better even at 50 MPH, but I suspect there's better uses of your money and effort to spend on something else. And since they are so popular, an all-original no-overdrive "driver-or-better condition" car is getting pretty rare to see in the 4+ rear axle era.

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These points might not actually always be the case, unless someone's calculated the engine load with the applicable air-dynamics and gear ratios for a given vehicle.
I've watched a 1940-s Mopar (I think) video where they've calculated the gas usage, etc. The most economical speed was 35 MPH. And the numbers were like 3x times as high at 70 MPH... But this is not only about the engine RPMs, though; there are plenty of other factors to consider, including the engine specs

Overdrive will not diminish aerodynamic drag, but it offers many other advantages. Fuel and oil economy are improved under most all operating conditions, and engine wear is reduced substantially. Engine noise level is reduced. Absolute top speed on level ground may not improve, much, if any, but that's not the aim of adding overdrive. Moving the car 100 miles down the highway while the engine only sees 70 miles has several obvious advantages. Packard engines have good low and mid-range torque, which makes them well-suited for use with overdrive. In those rare instances where conditions are not suited for use of overdrive, such as running up Pike's Peak into a headwind, or running down Pike's Peak pulling a trailer, it can be conveniently locked out as needed. Overdrive retains all the advantages of a low geared axle ratio, such as excellent acceleration in city traffic with minimal gear-shifting and easy clutch engagement, while adding the advantages of high speed gearing whenever conditions warrant.

I think some period ads indicated that OD reduced engine speed by 30% when engaged and improved on-the-road MPG by "up to 20%", which is plausible. Engine wear would be substantially reduced, assuming the vehicle was properly maintained and spent a good proportion of total miles driven on the open road in overdrive mode.

Here is the official sales claims for benefits and advantages as published in the 39 fact book. Lists all the reasons why a reluctant customer might want to part with a fair amount of money to buy the option. I believe other mfgs had OD a few years before Packard's first use in 39.








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