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Overdrive Operation Help


ricosan

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Hey Guys,

I've owned my Marmon for about six months now but I have yet to engage the Overdrive. This Overdrive is totally mechanical. A few months ago, the restoration shop I take my car to pointed out that the cable that engaged the Overdrive was sliding in its clamp attached the the side of the transmission. I was able to remedy this last month but I still can't get a reduction in rpms after engagement.

When the Overdrive is not engaged, the car "freewheels" but when I engage the Overdrive, the free wheeling is no longer active and the car operates like a normal transmission. I am able to use the engine to slow down, a feeling that I like.

My problem is I my shift doesn't give me a higher gear. Do I have the adjustment too far one way or the other on the cable, or am I not following the proper sequence for engagement?

I have been engaging the system by going above 30 mph, push in the clutch, push in the lever under the dash, slight crunch, then no more "free wheeling" but no higher gear.

ricosan

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I don't know about Marmons but on most old cars pulling the handle out locked out overdrive. Pushing it in allowed overdrive. The fact that it freewheels indicates you are in the overdrive position. Are you sure your car has overdrive and not just freewheeling?

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I'm pretty sure that you have freewheeling, but not overdrive.

Most of the overdrive systems in high-dollar cars had a centrifugal device that engaged overdrive when you reached a certain speed, usually around 30mph. Just a slight lift off the throttle will let the OD engage.

Many 31 and later high dollar cars had free wheeling, it helped make silent up shifts, without synchromesh, But the lack of engine braking made it unpopular, and maybe unsafe for those drivers who don't understand it's function.

By the way, NEVER go from free wheeling to 'lock out freewheeling' with the engine speed not matching the road speed. YOU WILL DESTROY THE FREEWHEELING MECHANISM. Always use enough throttle to apply a bit of slight acceleration then lock it out..

GLong

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Thanks for the response guys. I was told by a the dealer that I purchased the car from that it was equipped with an overdrive transmission.

Greg, are you saying that the likely use of the handle under the dash is used only to disengage freewheeling function? I'm so disappointed. Is this how many freewheeling autos of this era were equipped?

Does this mean that it won't hurt anything if I leave it out of freewheeling all together and run with the transmission in non- freewheeling mode all the time?

ricosan

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I have never driven a car with freewheeling so I have no personal experience but do know that it was not overly popular for the reasons mentioned above. I believe that car came from an estate of a well known Marmon club member before landing with the dealer. I'm willing to bet it was never driven by the dealer so he didn't realize it had freewheeling and not overdrive.

If you think you are revving to high for comfortable driving you can go with a high speed rear end of an after-market overdrive. Like I said, I don't think there was ever a factory Marmon overdrive.

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Hi Ricoman. yes, I believe it is only a freewheeling control. My '33 Pierce Arrow is the same way, but the control is labeled "FreeWheeling'. I never use freewheeling, it is always locked. A 5000 pound car needs engine deceleration. I installed an aftermarket OD in my Pierce to reduce engine rpm. Pierce did not offer a factory overdrive until the 1936 model year.

Contact members in the Marmon club and find out if the Marmon ever had a factory overdrive.

GLong

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I have to agree with GLong, it sounds like freewheeling, not overdrive. A lot of people get them confused since freewheeling was used in conjunction with early Borg-Warner overdrives. But what you're describing is exactly how freewheeling works and I don't believe that Marmon offered an overdrive in-period. If the car is original (and it should be obvious if an overdrive has been added), then I'm guessing it's just freewheeling.

And I'll agree that I HATE freewheeling. It's a necessary evil with the overdrive I have installed in my '29 Cadillac, and it's simply terrifying to use the car with it activated and not in overdrive mode (where freewheeling is deactivated). I can't believe there wasn't blood running in the streets and hundreds of small fires from brakes overheating back in the day. What kind of lunatic thought this was a good idea?!?

Leave the freewheeling feature disengaged and you won't hurt anything. Having some engine braking is far, far safer.

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Lots of cars in 1931-33 had free wheeling including my 1933 Graham. Your transmission looks too small to be overdrive, the section of the transmission that holds the freewheel/overdrive (round section of transmission just in front of the back of the transmission) free wheel is around 4 inches wide, overdrive is more like 6 inches wide (I have both types of transmissions, the mechanical section of the transmission is almost identical between the two). Here is the sales kick for free wheel if I understand it correctly (I also leave mine disengaged, lots of hills my me)...engage the car in first gear, once the car is moving you do not need the clutch to shift the car 2nd and 3rd (with freewheel engaged) the second selling tool was increased fuel mileage. The freewheel should automatically disengage in reverse, a mechanical interlock, you can not run the planetary gear in reverse.

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I would say factory overdrive would be at least a 1-3 thousand dollar bump in the value. The Gear Vendors overdrive is a great unit when properly installed and makes driving these cars at 50-60+ mph a pleasure. With correct brake lining, stopping should not be a problem. I have a friend with a 1938 Graham with factory overdrive he can drive 70mph all day long, he is running a bone stock supercharged six!

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  • 1 year later...

A stock Borg Warner overdrive went into the freewheeling mode if under 28 mph and automatically into overdrive if over 28 mph at which time it was not freewheeling anymore. I drive mine in the freewheeling mode under 28 mph all the time as at that low of a speed the brakes are fine and freewheeling is real smooth and easy on the drivetrain, by applying slight pressure on the accelerator pedal the engine is once again connected to the rear end thru the overdrive unit. Over 28 mph it goes into overdrive with the higher gear ratio very apparent. I can also just leave the lever pulled towards me and the car drives just like a stock 38 Buick without an overdrive no matter what the speed is. 

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Freewheeling mode is similar to an automatic where there is little engine braking. We are happy with that, so what is the problem with freewheeling? ;)

 

In the Studebaker (1938-39) you cannot engage reverse in freewheeling+o/d mode. This is because of the way the freewheeling unit works. It consists of a number of ramps and rollers. In drive, the rollers run up the ramps and lock between the ramps and the inside of a housing connected to the drive shaft. When the gearbox is driven from the rear (foot off accelerator), the rollers run down the ramps and the housing and drive shaft are disconnected from the engine drive. Reverse is the same action. So there has to be a way to disconnect freewheeling to go in reverse. In the Studebaker version of the Borg Warner, you disengage o/d and a rod pushes a sleeve back. It is a simple cam arrangement on the lever you move with the cable. The inside of the sleeve has splines that engage with similar splines on the front of the ramps and the outside of the ramp-roller housing to lock them together. So the drive goes to the ramp, into the sleeve then back into the rear housing and drive shaft.

 

The manual says one should not disengage f/w while in motion. The grinding is the sleeve grinding on the ramp and housing splines.

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