Hello All,
One of the things I'd like to change about my 50 Commodore is the overdrive engagement speed, which is at about 18-20 mph. I've been searching the forums to see if anyone has reliably changed the engagement speed of the overdrive on the stepdowns, and only found the same question posed a couple years ago without any luck of a solid answer.
http://forum.hetclub.org/discussion/164130/overdrive-governor-adjustment/p1
I performed the same change on the Bendix governor used on another Warner overdrive. However, my 50 Commodore uses the Autolite governor (I think due to Supermatic circuitry). So, I put my engineering background to use to determine what I could modify to achieve about a 30 mph engagement.
I opened the governor to understand the mechanism and found a delicate switch mechanism as part of the cap and a very husky set of 8 weights and a coil spring. The math says that the force on the spring grows with the square of the vehicle velocity. So, to increase the engagement speed, I could either reduce the weights or increase the spring. In order to make the change reversible, I tried the spring method first.
After lots of measurement to determine the spring dimensions, its force rate and its force at the moment of switching. After lots of calculations and searching several spring suppliers' catalogs, I came up with a candidate spring, shooting for an engagement of 30-35 mph. After receiving the spring, the fun began.
Yesterday, I reassembled and reinstalled it, then took the car for a test drive. I am happy to report the engagement speed is nearly right on target at about 32 mph. This makes the 2nd to 3rd shift better for my driving style, then letting the system shift to 3rd OD. Instead of having to decide whether to shift into third prematurely (to prevent going from 2nd non-OD to 3rd OD) or letting OD kick in during second (which is a bit abrupt), then shifting into 3rd OD.
The process is a bit delicate, requiring the removal and replacement of the rivet the holds a collar in place, the unbending (without breaking) several small tabs on the spinning internal cup that holds the weights and finally, reassembling the weights into their clever little retainer.
I can explain deeper if anyone is interested.
Pat,
Bellbrook, Ohio
Pat, very interesting note here. Thanks for sharing.
Pat,
Please consider writing up a "Tech Bulletin" and submit it to the White Triangle for publishing.
Nice work.
Thanks, Guys.
Ed, I'll try to put the whole journey together and submit it to WT. I have some photos of the process and may use a spare governor I have to get some more and better photos.
As a side note, for cars with SuperMatic function, this also changes the automatic 2nd to 3rd shift speed.
Fun stuff. For me, it has truly improved the driving experience.
Pat
I just received a few more spring types for additional OD engagement speeds. I'll be measuring and trying them soon.
Hello all,
I have a spare OD governor that I plan to modify to get the higher OD engagement speed, and will be taking some additional photos for better documentation. With the modified/tuned spring, the OD engagement speed is right at 30mph. Anyone interested in buying it once it's done?
I still plan on sharing the process as a Tech write up, just busy with the family priorities and that pesky thing called work.
Pat
I am interested, Pat. Is it the same governor used in a 1954 Hornet? Mine runs at 12 volts, but since it is basically a grounding switch, I don't think the voltage matters.
You are correct that the governor is simply an switch to ground and therefore, voltage does not matter. Whether the governor is the same as on my 50, I don't know.
having no replies in over a year on this, I hadn't been focused on it.
For reference, I know that in the 48-51 years, there were two different connector styles on essentially the same governor, we'd need to compare part numbers in the library to confirm. I am confident the centrifugal switch mechanism in yours, however, is either the Autolite or Bendix type and can be modified for higher speed engagement.
Pat
Dr. Bob,
I've not done any further research over the weekend to determine compatibility. Can you locate a photo of it, or one comparable. I'll still plan to find and unpack the ones I have, then post a photo.
Pat
Here are some photos of my governor on the car.
The governor body appears to be the same as what I have, but the switch cap and connection is different. I conclude it is the Autolite type, with the common internals. I don't know whether an earlier unit would fit in and mate to the driven gear adapter. Perhaps one of the parts experts here can comment.
If you like, I am happy to modify yours with the stronger, tuned spring for higher engagement speed. The operation does not prevent reversal back to the original parts.
This, of course, has the down side of having to remove, ship and wait for the part.
Pat
Hi, Pat,
The removal, shipping, and waiting are a downside. I had someone rebuild my Ranco valve, but the car was driveable without it.
I'd be interested in the tech writeup. Also, do you have a part number or specs on the spring you used?
I discovered the reason they set the governors at 18-22 MPH. You can drive around town leaving the car in 2nd gear: get going in 2nd, then lift the gas at 20 MPH to shift in 2nd + overdrive, which is about the same as 3rd gear. When you slow down, the car "shifts" to 2nd no overdrive automatically. But I find that in modern traffic, I am sometimes going 18-22 when I shift from 2nd to 3rd, so I end up going from 2nd no overdrive to 3rd with overdrive, skipping 3rd no overdrive. If I'm on a steep hill, that's too tall to get power at 20 MPH.
To make matters worse, the owner before me didn't understand the OD wiring, and he rewired the internals of the OD relay so that the OD kickdown switch would not work at all. The OD kickdown switch was inoperative as a result. I had to take it apart and reattach the coil wires to the correct external contacts.
While I was doing that, I figured out how to add a second kickdown switch/light on the dashboard so that either the dash kickdown or the under-the-pedal kickdown will work (hint: N.O. contacts are wired in parallel, N.C. contacts are wired in series). I wired the light on the dash switch between ignition and the kickdown wire that connects to the OD solenoid (which is grounded only if the car is actually in OD). That causes the light on the switch to be lit when the car is actually in OD. That way I know if the unintentional 3rd with overdrive shift happened.
But clearly your solution of bumping up the governor to 30 MPH would be a better solution. So I hope you can give me some hints about the spring and any tricks needed to install it.
Check some of the owner manuals and you'll see that the original cut-in speed was more like 26-28 mph. The governors evidently cut in at lower speed as they age.
I'll need to look up the spring/vendor details. Essentially, the change involves opening the outer governor
From the images, I am wondering whether the 54 governor is a bit longer than the earlier versions. If so, that would introduce the possibility a different spring would be needed. The process I used included analytical calculation to begin the guess at which spring to use, but ultimately, a bench test of switch speed and car test for confirmation were used. The bench test involves a variable speed speedometer tester with tachometer that can tell me the point at which the governor switches. I then correlate this to a desired vehicle switch speed.
Attached are photos of a disassembled Autolite governor from my 50 Commodore Six with Supermatic. The photos only show the internal rotating weight chamber and its innards, not the outer governor casting.
Notice the spring in each photo. If this spring is replaced with a stronger spring, the governor engagement speed will increase. Caution, the tangs on the rotating chamber are delicate.
I have some clarifying information for this thread, so even though it is a few years later, here goes. The cut-in speed of the OD governor depends on the rear axle ratio. On the open forum it has been stated that the governor is set to activate the relay at around 20-25 mph with the 4.55 rear end. With the optional 4.11 rear end, the upper end would be about 28 mph. Given that my speedometer may not be quite accurate, my observed cut-in speed matches this information. Thus, there is no reason to believe that the cut-in speed of an OD governor decreases with age.
Since I am not interested in the Mickey Mouse automatic transmission mode that motivated coupling a 4.55 rear axle ratio with a 3 speed OD transmission (i.e., getting started in 2nd gear around town and using the OD to shift between 2nd and 2nd-with-OD=3rd) and I am not planning to pull out any stumps, I think the solution is to change my Dana rear end from a 4.55 to a 4.11 or maybe even a 3.92. That will raise my cut-in speed to close to 30 mph, where I think it ought to be.
I'd be interested to know if my reasoning matches real world experience.
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