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Overdrive Function: Hopefully make a sticky thread from this. EDIT: I added new information. (9/13)

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  • '66Commander
    replied
    st w/OD, 2nd w/OD and 3rdst, 2nd, 3rdSo what is Overdrive?
    Overdrive changes the gear ration from the input shaft in the gear box. It changes the ratio to reduce the engine RPMs by 30%; thus effectively reducing the engine noise and vibration to half. It is located on the underside of the car, between the transmission and the driveshaft.

    What is the goal of Overdrive?
    The goal of overdrive is to reduce RPMs. This will lower engine wear, produce better gas, however this will limit your top speed. How this is possible is that it takes 12 horse power (HP) to drive a car at 40MPH. However, there must be an additional 18HP to make up for overall power-plant loss. With OD engaged, it reduces the additional HP from 18, to 11. Making the overall HP at 40MPH 23 (OD engaged) v. 30 (OD disengaged.)
    When the car is below Cut-in Speed (CiS) the car is in Direct Drive (DD). For example, when my 3 Speed w/ OD 1966 Commander is in 3rd the gear ratio is 1:1, Transmission Input shaft:Transmission Output Shaft. But when you are at or above the CiS you can engage OD. This would change your ratio to .7:1, Transmission Input shaft:Transmission Output Shaft.

    How do I make OD available, and engage it?When is it appropriate to use OD?
    It is best to use OD when driving on flat ground. Especially on long stretched driving. Like the freeway. You can also leave OD so it is available while you are driving around in the city. Some folks prefer to leave it available to them.
    HOWEVER!! If you live in a mountainous area, like myself, it is best to leave it unavailable. Unless you are going onto the freeway of course. If you are using engine brakes you want to ensure OD is disengaged, and unavailable, just to make sure. When OD is enable the transmission is freewheeling. And will not have engine brake capabilities. Be careful.

    Parking w/ OD! PLEASE READ!
    Parking w/ OD is a little different than normal. If you have OD engaged then you want to put your car into Reverse. This will prevent your Studebaker from rolling away. No one wants that to happen.


    I've taken this knowledge from various posts on this forum, along with the manual for the OD.
    If you would like to read it:
    http://www.tocmp.com/manuals/trans/B...rive/index.htm


    Again, please let me know of any corrections I should make, or any suggestions. When it reaches a point that we can all agree on, I will post a "final" copy of it and request that it is made sticky.
    Last edited by '66Commander; 09-27-2013, 01:10 PM. Reason: Just putting the original first post here for reference.

    Leave a comment:


  • '66Commander
    replied
    Added information below:
    The new information below explains city driving, and how OD works. Again, please let me know of errors, suggestions and etc.

    Before I explain what Overdrive is, let me explain a few terms:So what is Overdrive?
    Overdrive changes the gear ratio from the output shaft in the gear box. It changes the ratio to reduce the engine RPMs by 30%; thus effectively reducing the engine noise and vibration to half.

    What is the goal of Overdrive?
    The goal of overdrive is to reduce engine RPMs. This will reduce engine wear, reduce fuel and oil consumption. However this will limit your top speed.
    With overdrive available, and the car is below Cut-in Speed the car is in Direct Drive (DD). For example, when my 3 Speed w/ OD 1966 Commander is in 3rd the gear ratio is 1:1; the Transmission Input shaft and Transmission Output Shaft are turning the same revolutions per minute. But when you are at or above the Cut-in Speed you can engage OD. This would change your ratio to 0.72:1, Transmission Input shaft:Transmission Output Shaft.

    How do I make OD available, and engage it?When is it appropriate to use OD?
    It is best to use OD when driving on flat ground. Especially on long stretched driving. Like the freeway. You can also leave OD so it is available while you are driving around in the city. Some folks prefer to do that.
    HOWEVER!! If you live in a mountainous area, like myself, it is best to leave it unavailable. Unless you are going onto the freeway of course. If you are using engine braking you want to ensure OD is locked out (knob completely pulled out). When OD is enabled and/or available, the transmission will be freewheeling and you lose your engine braking capabilities. Be careful.
    Also, you do not want to engage OD while in 1st gear. The engine will be unable to handle the torque, and you will be at risk of blowing your engine. Let alone that being in first gear and at the cut-in speed is bad in of its self. It is okay to have OD available, just not engaged.

    How can I use it in city driving? [Taken from Borg-Warner manual]
    Considering that most intercity speed limits are 25 to 35mph you can use 2nd w/ OD as a 3rd gear. This is entirely up to you.
    With most stops within the city some drivers like to start their car in 2nd gear DD. Once they accelerate to cut-in speed, they would engage OD. The gear ratio of 3rd DD is similar 2nd w/ OD in most vehicles. Stopping would consist of the normal, pushing the clutch pedal and using the brakes to stop. And if you needed the torque of 2nd DD all you would have to do is disengage the OD.
    However, some folks like to use OD as a fourth gear. E.g. 1st, 2nd, 3rd, 3rd w/ OD. This is the same concept used on modern cars such as a 5 speed transmission. Where the 4th gear is a 1:1 ratio. (For every rotation of the crankshaft, the output shaft of the transmission makes one rotation.) Then the 5th gear would act as 4th w/ OD. Where the ratio would be X:1.

    How does OD work?
    For starters, below are six pictures. These are taken out of the Borg-Warner manual linked below. Pages 8, 9, and 10.
    Click image for larger version

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    This is the Sun gear assembly (Above). When OD is engaged the power goes from the Sun gear (center gear) into the three pinions, then into the ring gear (Outermost gear). Then from the ring gear it goes to the output shaft.
    Click image for larger version

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    Above are two examples in one picture.
    On the left we have OD available/disengaged. When OD is available the pawl rests on the blocking ring. Allowing the Sun gear-control plate to spin.
    On the right we have OD engaged. When OD is engaged the pawl is now in between teeth on the Sun gear-control plate. The control plate is now stationary.
    Click image for larger version

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    Above we have OD unavailable. The tab on the lower right (of the above picture) is pointing towards the solenoid.
    When OD is unavailable the control shaft and the control fork are shifted backwards, making the Sun gear to connect with the lockup teeth. This makes all the gears move as a unit. Making the ratio 1:1.
    Click image for larger version

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ID:	1683658Click image for larger version

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    Above we have two pictures. When the OD is available the tab on the bottom right corner is pointing away from the solenoid. This enables the solenoid to move the pawl from the blocking plate to the Sun gear-control plate, effectively engaging OD (Above Left). This then delivers the power (as explained on the top picture) to the Sun gear to the output shaft.
    When OD is available but disengaged (Above Right) the power is applied directly to the Freewheel unit. (Pictured below)
    Click image for larger version

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    Above is the Freewheeling unit. Freewheel unit is not the technical term, but for convenience I will refer it as such.
    Again, freewheeling is when OD is available, but disengaged.
    The power is delivered directly into the Freewheel cam. When driving torque (driving torque is when the accelerator is pressed) is applied the clutch rollers (contained within the roller cage) are pressed out against the outer race. From the outer race the power is delivered to the output shaft.
    When coasting (accelerator is not being pressed) the clutch rollers are released and are no longer holding the outer race. This allows the clutch rollers, mainshaft, and engine to rotate at a slower speed then the ring gear and output shaft.

    Parking w/ OD! PLEASE READ!
    Parking w/ OD is a little different than normal. If you have OD available then you want to put your car into Reverse. This will prevent your Studebaker from rolling away. No one wants that to happen.

    I've taken this knowledge from various posts on this forum, along with the manual for the OD.
    If you would like to read it the manual click here:
    http://www.tocmp.com/manuals/trans/B...rive/index.htm
    It explains what it is, and how it works. Much a deeper take then this post.
    Last edited by '66Commander; 09-13-2013, 01:58 PM.

    Leave a comment:


  • StudeRich
    replied
    Originally posted by jackb View Post
    /Cut/By habit, I now pull out the handle and disengage OD for parking. OD is for long drives in open country......(speaking from Mass)
    OR, do what most of us do, when driving an Overdrive equipped Car, just always remember to Park in Reverse, it's each just like putting an Automatic in Park, an almost automatic reaction that becomes a habit.

    That way you never have to worry about whether or not it is in O.D. or Out of O.D. it always holds.

    Leave a comment:


  • jackb
    replied
    as has been said above: the OD unit is supposed to be enabled when you expect a longer drive in flat or lightly rolling terrain.....excepting 2nd/2nd around town, in traffic. And I think this has been made clear above: you never need to use the clutch until stopping the car. By habit, I now pull out the handle and disengage OD for parking. OD is for long drives in open country......(speaking from Mass)

    Leave a comment:


  • '66Commander
    replied
    Originally posted by gordr View Post
    The overdrive unit cannot handle the torque of your engine, six or eight, multiplied by the ratio of first gear. Ask me how I know! Fact is, even the lesser torque multiplication of second gear is a bit much for the R10 (three planet) OD unit, unless you drive it gently, but going back and forth between second / second OD is so darn handy for city driving that nearly everybody does it. Just treat it with respect.
    Okay. Now I understand. Thank you for the revision suggestions

    Originally posted by StudeRich View Post
    One of Gord's suggestions that you still do not understand and missed again, is that although Overdrive "is available" with the Knob "IN" in low Gear, it is not wise to rev the Engine to 4500 or whatever it takes to reach 28-32 MPH in LOW GEAR!
    Buy doing that and simply releasing the Gas pedal it WILL shift with quite a snap.

    Even though most of us that had V8's, did try it in our younger years, it certainly can't be good for the Overdrive Unit and I would not do it now. If you had a 6 Cyl. you would be lucky if you did not blow the Engine revving it high enough to reach 30 MPH. That is why Gord wanted you to just not mention 1st. Gear.
    Just like I said to gordr now I understand. I honestly didn't know. Thank you too


    Again, the revision is in red.

    Before I explain what Overdrive is, let me explain a few terms:So what is Overdrive?
    Overdrive changes the gear ratio from the output shaft in the gear box. It changes the ratio to reduce the engine RPMs by 30%; thus effectively reducing the engine noise and vibration to half.

    What is the goal of Overdrive?
    The goal of overdrive is to reduce engine RPMs. This will reduce engine wear, reduce fuel and oil consumption. However this will limit your top speed.
    With overdrive available, and the car is below Cut-in Speed the car is in Direct Drive (DD). For example, when my 3 Speed w/ OD 1966 Commander is in 3rd the gear ratio is 1:1; the Transmission Input shaft and Transmission Output Shaft are turning the same revolutions per minute. But when you are at or above the Cut-in Speed you can engage OD. This would change your ratio to 0.72:1, Transmission Input shaft:Transmission Output Shaft.

    How do I make OD available, and engage it?When is it appropriate to use OD?
    It is best to use OD when driving on flat ground. Especially on long stretched driving. Like the freeway. You can also leave OD so it is available while you are driving around in the city. Some folks prefer to do that.
    HOWEVER!! If you live in a mountainous area, like myself, it is best to leave it unavailable. Unless you are going onto the freeway of course. If you are using engine braking you want to ensure OD is locked out (knob completely pulled out). When OD is enabled and/or available, the transmission will be freewheeling and you lose your engine braking capabilities. Be careful.
    Also, you do not want to engage OD while in 1st gear. The engine will be unable to handle the torque, and you will be at risk of blowing your engine. Let alone that being in first gear and at the cut-in speed is bad in of its self. It is okay to have OD available, just not engaged.

    Parking w/ OD! PLEASE READ!
    Parking w/ OD is a little different than normal. If you have OD available then you want to put your car into Reverse. This will prevent your Studebaker from rolling away. No one wants that to happen.

    I've taken this knowledge from various posts on this forum, along with the manual for the OD.
    If you would like to read it the manual click here:
    http://www.tocmp.com/manuals/trans/B...rive/index.htm
    It explains what it is, and how it works. Much a deeper take then this post.

    Leave a comment:


  • jclary
    replied
    "Back in the day"(there's that phrase again)...I have driven Mack trucks with the old twin shift lever "duplex" transmissions. One lever runs it through the gears and the other lever is the "hi-low" range for each gear. In the days before turbos were common for diesel engine tractors, that old duplex, although a bit ungainly, was necessary, for chugging over the next hill.

    My Studebaker fleet includes a car and a truck with overdrive. Although I have used overdrive in second once, out of curiosity...I consider it as ONLY a fourth gear. Anyone who has held the sun gear assembly in their hands, and admires the genius of the design...should know better than abuse it.

    Leave a comment:


  • gordr
    replied
    The overdrive unit cannot handle the torque of your engine, six or eight, multiplied by the ratio of first gear. Ask me how I know! Fact is, even the lesser torque multiplication of second gear is a bit much for the R10 (three planet) OD unit, unless you drive it gently, but going back and forth between second / second OD is so darn handy for city driving that nearly everybody does it. Just treat it with respect.

    Leave a comment:


  • StudeRich
    replied
    One of Gord's suggestions that you still do not understand and missed again, is that although Overdrive "is available" with the Knob "IN" in low Gear, it is not wise to rev the Engine to 4500 or whatever it takes to reach 28-32 MPH in LOW GEAR!
    Buy doing that and simply releasing the Gas pedal it WILL shift with quite a snap.

    Even though most of us that had V8's, did try it in our younger years, it certainly can't be good for the Overdrive Unit and I would not do it now. If you had a 6 Cyl. you would be lucky if you did not blow the Engine revving it high enough to reach 30 MPH. That is why Gord wanted you to just not mention 1st. Gear.

    Leave a comment:


  • '66Commander
    replied
    No worries.
    Sactorandy asked about it too.
    Today is busier then normal today at work, but I will do some studying. When/if I get it written up I'll add it onto the post.

    Leave a comment:


  • wittsend
    replied
    Originally Posted by StudeRich
    But really, the way I understand the intent of this string was to explain it's use, not HOW it works.


    Statement by 66 Commander: "Exactly. I do not know the mechanics of it my self. I also statred this string so I can learn how to use OD myself. "

    ----

    My apology. It was stated in post #1 "Again, please let me know of any corrections I should make, or any suggestions." The intention of my post was to simply say I didn't under the Cut-in Speed. If I understood HOW it worked then I might understand the application of the function. Some of us learn that way. As a "suggestion" I felt it was self evident.

    The original post also included a "basics" of the overdrive. I took it to mean this was not (just) a discussion amongst "those in the know"..., but an attempt to enlighten those who didn't. Like me. I was simply trying to learn. Not be disruptive.

    Tom

    Leave a comment:


  • '66Commander
    replied
    (Quotes from other folks are further down)
    Originally posted by gordr View Post
    Some suggested edits inserted
    (Questions/comments I have to some revisions are numbered in the quotation box below)

    1: With the 1st w/ OD some people say that they always have OD on. Even in 1st gear.
    What is the problem if it is in 1st w/ OD? Perhaps I can add a warning?
    2: How come?
    3: I'm trying to make this kinda simple. I'm not going to lie, when I first started with my Studebaker, I wouldn't have know what "an extra planetary gearset" would mean. Granted, most people who work on cars know what this means. But I just want to try and cover as many bases as I can.
    4: Why not? On one of the posts on this forum (I can't remember what one) it said that this isn't necessary, but it helps prevent wear.
    5: I do like this sentence. However, how would this take effect? According to the Borg-Warner manual it says that it will disengage by itself.
    I'm on the fence on if I want to use enabled v. available. Because, to me at least, enabled means it is on. Where as available means the option is there. What is everyone else's thoughts?

    Thank you. The revisions I used are highlighted red.

    Before I explain what Overdrive is, let me explain a few terms:


    This is commonly known as "overdrive locked out".

    in overdrive gear. E.g. 1st w/OD *see quote above*, 2nd w/OD and 3rd w/OD.
    and the transmission's free wheeling is in effect, meaning no engine braking. E.g. 1st, 2nd, 3rd.

    may engage, if it is available". This speed is 20 to 32 mph. (Depending on make/model)

    So what is Overdrive?
    Overdrive changes the gear ratio from the output shaft in the gear box. It changes the ratio to reduce the engine RPMs by 30%; thus effectively reducing the engine noise and vibration to half.

    What is the goal of Overdrive?
    The goal of overdrive is to reduce engine RPMs. This will reduce engine wear, reduce fuel and oil consumption. However this will limit your top speed.
    With overdrive available, and the car is below Cut-in Speed the car is in Direct Drive (DD). For example, when my 3 Speed w/ OD 1966 Commander is in 3rd the gear ratio is 1:1; the Transmission Input shaft and Transmission Output Shaft are turning the same revolutions per minute. But when you are at or above the Cut-in Speed you can engage OD. This would change your ratio to 0.72:1, Transmission Input shaft:Transmission Output Shaft.

    How do I make OD available, and engage it?

    all the way out.
    To engage OD ensure that OD is available (knob in), and when at or above cut-in speed; briefly release the gas pedal. You will be able to hear the RPMs drop. And then drive as normal from there.
    To disengage OD simply press the gas pedal all the way to the floor to activate the kickdown circuit. This will drop the car back to DD third (no overdrive), raising the RPMs, disengaging OD. You would do this, for example when passing another vehicle, or ascending a steep hill.cut-in speed the OD will automatically disengage itself.

    When is it appropriate to use OD?
    It is best to use OD when driving on flat ground. Especially on long stretched driving. Like the freeway. You can also leave OD so it is available while you are driving around in the city. Some folks prefer to do that.
    HOWEVER!! If you live in a mountainous area, like myself, it is best to leave it unavailable. Unless you are going onto the freeway of course. If you are using engine braking you want to ensure OD is locked out (knob completely pulled out). When OD is enabled and/or available, the transmission will be freewheeling and you lose your engine braking capabilities. Be careful.

    Parking w/ OD! PLEASE READ!
    Parking w/ OD is a little different than normal. If you have OD available then you want to put your car into Reverse. This will prevent your Studebaker from rolling away. No one wants that to happen.

    I've taken this knowledge from various posts on this forum, along with the manual for the OD.
    If you would like to read it the manual click here:
    http://www.tocmp.com/manuals/trans/B...rive/index.htm
    It explains what it is, and how it works. Much a deeper take then this post.

    Originally posted by sactorandy View Post
    Perhaps a brief discription of the external OD parts and their operation would be helpful. IE: solenoid, speed governer, relay, reverse lock-out switch, and throttle kick-down switch. This has been a learning curve for me over the last 2 years on my 55 Champion. I bi-passed everything and connected the solenoid directly to a toggle switch and now the world is good again. Thanks for trying to clarify this mystery for those of us that know just enough to get into trouble.

    Randy
    I have thought about that, but I decided to make this more about the bare-bones and how it works. Also, I'm not familiar with how it works itself. I actually started it because I was researching a correct way to use it. But if a couple more folks think it would be beneficial to have that explanation, I am more then willing to do it. Or if I have enough free time haha.

    Originally posted by omstude View Post
    Ah, overdrive, what a great transmission! Yes, the owners manuals are quite good and concise about explaining how to operate overdrive. It's really not hard when you get the hang of it. I basically learned to drive on my 52 Land Cruiser so it's second nature to me. The only way real damage can result from operator error is if you don't know how properly to lock it out while driving. I once had the brakes fail on my 52 while descending a steep hill in a suburban area with the overdrive engaged. I was freewheeling so I had to accelerate enough to engage the transmission in third gear, pull out the overdrive lever, downshift to second, pull the parking brake as hard as I could and leave most of my right front tires white wall on the curb in order to stop.
    It definitely will become easier once one gets the hang of it. But til then it can be confusing. Least for me it was.
    Oh wow! I'm glad that you and your Stude are okay. Kinda reminds me of when I found out that my brakes and parking brake didn't work... the hard way.

    Leave a comment:


  • omstude
    replied
    Ah, overdrive, what a great transmission! Yes, the owners manuals are quite good and concise about explaining how to operate overdrive. It's really not hard when you get the hang of it. I basically learned to drive on my 52 Land Cruiser so it's second nature to me. The only way real damage can result from operator error is if you don't know how properly to lock it out while driving. I once had the brakes fail on my 52 while descending a steep hill in a suburban area with the overdrive engaged. I was freewheeling so I had to accelerate enough to engage the transmission in third gear, pull out the overdrive lever, downshift to second, pull the parking brake as hard as I could and leave most of my right front tires white wall on the curb in order to stop.

    Leave a comment:


  • greyben
    replied
    My 1955 owner's manual gives a clear and concise explanation on how to use overdrive covering all modes of operation. Since overdrive operation remained the same from about 1939 through the end of production it is assumed that all relevant owners manuals would give the same description. The shop manual gives a good description of the mechanical operation. If you had access to the planetary gear assembly it would be even clearer.

    I believe the actual gear reduction ratio is 0.72 although this was frequently referred to as approximately 0.7

    Leave a comment:


  • gordr
    replied

    Leave a comment:


  • '66Commander
    replied
    Originally posted by BobPalma View Post
    [wouldn't it be "by 30%," rather than "to half?"]
    That is what I would have thought too. But according to the Borg-Warner manual it is by half. (Page 6 Section 2. Comfort, bullet b.)
    Strange right?

    Originally posted by StudeRich View Post
    But really, the way I understand the intent of this string was to explain it's use, not HOW it works.
    Exactly. I do not know the mechanics of it my self. I also statred this string so I can learn how to use OD myself.

    So, here we go with revisions:So what is Overdrive?
    Overdrive changes the gear ratio from the input shaft in the gear box. It changes the ratio to reduce the engine RPMs by 30%; thus effectively reducing the engine noise and vibration to half. [wouldn't it be "by 30%," rather than "to half?"]

    What is the goal of Overdrive?
    The goal of overdrive is to reduce engine RPMs. This will lower engine wear, produce better gas mileage, however this will limit your top speed.
    For an example of how this is possible is that it takes 12 horse power (HP) to drive a car at 40MPH. However, there must be an additional 18HP to make up for overall power-plant loss. With OD engaged, it reduces the additional HP from 18, to 11. Making the overall HP at 40MPH 23 (OD engaged) v. 30 (OD disengaged.) Now this may vary from car to car. [This may not be very important to how it works, but it was in the Borg-Warner manual. I figured it would give a brief explanation of what it does.]

    When the car is below Cut-in Speed (CiS) the car is in Direct Drive (DD). For example, when my 3 Speed w/ OD 1966 Commander is in 3rd the gear ratio is 1:1; the Transmission Input shaft and Transmission Output Shaft are turning the same revolutions per minute. But when you are at or above the CiS you can engage OD. This would change your ratio to .7:1, Transmission Input shaft:Transmission Output Shaft.

    How do I make OD available, and engage it?When is it appropriate to use OD?
    It is best to use OD when driving on flat ground. Especially on long stretched driving. Like the freeway. You can also leave OD so it is available while you are driving around in the city. Some folks prefer to leave it available to them.
    HOWEVER!! If you live in a mountainous area, like myself, it is best to leave it unavailable. Unless you are going onto the freeway of course. If you are using engine brakes you want to ensure OD is disengaged, and unavailable, just to make sure. When OD is enable the transmission is freewheeling. And will not have engine brake capabilities. Be careful.

    Parking w/ OD! PLEASE READ!
    Parking w/ OD is a little different than normal. If you have OD engaged then you want to put your car into Reverse. This will prevent your Studebaker from rolling away. No one wants that to happen.


    I've taken this knowledge from various posts on this forum, along with the manual for the OD.
    If you would like to read it the manual click here:
    http://www.tocmp.com/manuals/trans/B...rive/index.htm
    It explains what it is, and how it works. Much a deeper take then this post.

    Leave a comment:

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