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How do I tell which overdrive I have? I need to order a wiring harness. My car is a 48 Custom 8 Club Sedan (2 door). The VIN on the cowl reads 2255-9-2723. Does that mean R9? An old Packard guy I talked to thinks I have an R11. How do I tell for sure?

Scrape off the grease on the o/d unit itself, the model designation is cast into the side of it.

Your car could have either, so another way without climbing under is to locate the OD relay on drivers side of firewall. The R9 has a black can near and similar in shape/size to voltage regulator with 6 wire terminals. The Rll has a smaller silver or natural can, with fuse on outside and 4 wire terminals.

If I am not mistaken, the "9" in your "2255-9-2723" indicates that your car is a 1949 model, not a 1948. And that being the case, you will most likely find that you have an R-11.

I have a similar situation with my 2262-9, which has an R-11.

Jay

Yes, Jay is right as always, the -9- indicates either a 1949 (but 22nd series) car, or less likely a 1948 left-over which was retagged by the factory to make it a 1949. The later is probably not the case due to the very low sequence #.

As already pointed out, there are differences between R-9 and R-11 in quite a few respects (both being equally functional) but the easiest way to tell is by the relay. Large black with 6 leads for R-9, smaller cadmium-covered relay with intergral fuse holder for the R-11.

Visually, there are several clues to determine which overdrive is in a given car. The R-9 has the solenoid located on the right side of the transmission and used 4 wires for control. The R-11 solenoid is on the left side and uses only 2 wires. The overdrive cases also have either the R-9 or R-11 designation cast on the top surface. From under the hood, if the control cable goes down the driver's side of the engine the car is equipped with the R-11. Conversely, if it goes down the passenger side, the car is equipped with an R-9. Also the relay, mounted on the fire wall, is twice as large for the R-9 as the one for the R-11 unit.

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Wow! This group is awesome. You have collectively answered my question very well. Under many years of grease I found an upside down R-11 on the case casting. The picture of relay adds further confirmation.

I am probably going to be a newbie at this business the rest of my life, but I did gain a little experience with the R-11 overdrive over the summer.

I did up a little webpage that explains (in newbie-speak) how the R-11 works, and how I repaired mine. I got lots of help and advice along the way. Click Here to see what I'm talking about. I hope it will be helpful to you.