While growing up in the ninetys on the central coast of california I had a good friend. His dad had, if I remeber corrrectly a 1958 Ford F-100. I can remember riding in the truck and askiing his dad how many speeds the truck had. He told me it was a three on the tree with an overdrive. Watching him drive I remember only seing him shift three gear ranges. I also can remember a **** that sad overdrive. Thinking back I can't really understand how that tranny got an overdrive. For instance my 1945 Ford 2N that I restored has a three speed manual transmission, sliding gear type. Now If I understand correctly My buddy's dads old truck had three speed selections on the column not four like a newer manual with four gear selections.

How was the overdrive factored in? I'm interested in how it worked. I can remember asking him one time how the overdrive works? He told me he had rebuilt acouple of times but couldnt get the overdrive to work properly? I also remember us driving to his ranch, and on the way there the tranny shifted but the driver did nothing to "shift" Gears?

I would like to get educated a bit on these mainly because I have the gift of an mechanical interested mind. I worked in a tranny shop for a year in high school and am going on two years at a diesel shop now in collage.

I would just like to know about the different variations of these intresting three speed "overdrive" Manual tranny's.

Basically How do they work?

Thanks in Advance John

 

They are an add-on planetary gearset that had a sprag clutch in them, such that they would not engage until you let off on the gas, when the unit is "enabled" by the cable under the dash.

 

Simply put, the overdrive is a gear built into a tailshaft housing bolted to the back of the three speed trans. My experience with one in a 56 Studebaker was when it didn't work it would freewheel rather than shift up.

One manufacturer was Borg Warner. They used an electric solenoid. When they worked properly you could split shift (6 gears). You could shift up by just taking your foot off the gas and when you were in the higher gear you could "tromp down" on the gas and the transmission would shift down for more power...commonly called a "passing gear".

I wish I had one.

That reminds me. My 56 Studebaker also had a hill holder clutch. If you had the clutch pedal depressed and stepped on the brake the clutch pedal held the brakes untill you released the clutch pedal...allowing you to have your foot off the brake to accelerate enough to get the vehicle moving without rolling backwards or killing the engine on a hill.

 

How does it work, it works good....real good. Atleast that's what Mr. Hodges told me back in '93 when I was at N.A.D.C.!

Good luck with your Auto/Diesel Classes, it changed my life, that's for sure.

As far as the overdrive unit goes, I'm told that is was only offered on '55 and later ford trucks, however, I have a late '54 that it is installed on, from factory, I know because my grandpa bought it new.

Like others have said, it is a planetary set that is installed in lieu of the tailshaft of the standard transmission. The unit has a solenoid (6v pos ground in my case) that engages a planetary set and causes an overdrive ratio (tail shaft drives the planets, ring gear drives the new tail shaft, solenoid holds the sun gear) for the new tail shaft.

I've heard rumors that there is a manual version available. Once you get up to speed you pull a lever and engage the planet set and have your overdrive. The problem with this is that there is a sprag clutch (one way roller) that must be disabled for the vehicle to move in reverse. This is accomplished on the electric installation by a governor that disengages the overdrive planet set once the speed drops below a setpoing (45mph in my case).

I had solenoid problems with mine for a while and plotted ways of manually engaging the planet set, but always worried about getting in the truck after a rum and coke, forgetting that the overdrive was engaged, and ripping the spragg clutch apart as I backed out of the parking spot!!

I found a place in California that sold solenoids, overdrive tail housings and whole transmissions if you could afford the shipping. Ordered a new solenoid, and was on my way......in overdrive!

As far as how it works, here is a control description:

Battery power is provided thru a fuse to an overdrive relay (6v relays are hens teeth) mounted on the firewall. Control power for the relay goes to the overdrive tailshaft governor (a centrifugal device that grounds upon a preset spring tension). Once the vehicle is moving at a certain speed, centrifugal force exceeds spring tension and the control power for the relay is grounded.

Once the relay is activated, battery voltage is applied thru a kickdown switch (normally closed) to the overdrive solenoid. This engages the solenoid and halts the sun gear, forcing an overdrive reduction to the ring gear/tail shaft. Note that you will have to let up on the gas momentarily to allow the solenoid to engage.

If the speed drops below the pre-set level, the governor will disengage the relay/solenoid and the overdrive condition will stop. Note that you must let up on the gas to allow the solenoid to disengage.

If, while the solenoid is engaged, you push the gas pedal to the floor, you will engage the kickdown switch. The kickdown switch (one normally open contact, one normally closed contact) is wired such that it will disengage the solenoid and ground the coil negative (to allow the engine to hesitate and the overdrive solenoid to disengage, simulating you letting off of the gas). When this happens, the overdrive is disabled and the transmission is functioning at 1:1. They call this a passing gear, it just disables the overdrive.

A funny thing happens when you are in second gear and going faster than the overdrive governor threshold (on my truck, if you are in second and going over 45mph), the overdrive activates and drives the output shaft into an overdrive reduction when the transmission is in second gear. This gives you another gear, between 2nd and 3rd. This also happens when in overdrive, over 45mph, and you downshift into second.

This is alot easier to understand when driving the truck and playing with the gears, especially if you have some rum handy! I have a great wiring schematic that may make it easier to understand. The schematic comes from a book entitled "Fix Your Ford" published in '68. Let me know and I'll scan the schematic for you.

Right there with you,

Ole' Green

 

Interesting I wonder why manufactureres stuck with three speed automatics for so long? And why they didn't use these tranny's but the old four speed granny's?

So the setup is similar to a gear vendors overdrive unit.

I wonder how the transition feels to overdrive, like an automatic?

 

The OD unit was also an option on the mid 50 sedans. I remember as a kid our next door neighbor had a white and yellow 55 2 dr he was very proud of and he would point out the OD emblem and **** on it to everyone and anyone.

 

You could put it in overdrive (pull out the lever) while you were accelerating or as long as there was a load on the engine and it wouldn't shift up (or down) untill you let off the gas.

The lower gear wasn't a granny gear, it was the standard 3 speed.

Do a search on "Borg Warner overdrive" and you'll find some more interesting stuff on them...They weren't perfect by any means but they are way cool.


So the setup is similar to a gear vendors overdrive unit.

 

When you engaged a B-W OD, it felt like a early-50's Slush-O-Matic. Especially since the OD ratio is a pretty significant 0.70, it is quite a drop in RPM. Very different than the British-made Laycock deNormanville OD, which shifts under power, and feels exactly like a modern automatic. The LdeN OD was a hyraulically engaged planetary actuated by a band just like an automatic.

Why didn't they go to 4-sp automatics and integral OD manual trans's sooner? Cost. Originally automatics were 4-speeds, then 3-sp's, all the way down to 2-speeds (PowerGlides), as gas got cheaper and cheaper, and people more affluent.

 

If you have a schematic i would love one please. I just got one of these trannies and installing it in a 68 F100. with a 390.

 

Dad had a 61 Bel Air with the 235 six cylinder and 3 speed manual with OD. He liked it so well he bought a 68 GMC 1/2 pickup with the 292 six cylinder and a 3 speed manual with OD.

The Bel Air would get 24 mpg on trips with all of us and our luggage. The GMC would get 23 mpg on a trip with no load in the bed.

I can remember dad having the truck in 2nd gear, letting out on the gas pedal (vacuum sensing switch turned the OD on/off unless it was locked out with the pull know in the dash) so it would go into OD in 2nd gear. Then when he stepped down on the gas pedal it would drop back to 2nd and spin the back tires when there was no load in the bed to give the tires more traction.

Didn't those 83 and 84 Corvettes with the Doug Nash 4+3 manual transmissions use a similar OD unit on the back of the transmission?

 

A friend in collage drove a 50s something Ford. I saw the overdrive and said “oh, you have overdrive” his answer…”just won’t stall”. Took me awhile to connect it to Hot Rod Lincoln.

 

Despite being in my 60's and having driven and owned lots of vehicles, I have never driven a car or truck with overdrive. Another thing I have never even seen is a 53-56 Ford truck with a stock automatic transmission.

 

Yeah, you’ve driven my truck. We just didn’t have it in overdrive.

 

That is true. You'll have to let me drive it when it is hooked up and working.

 

I believe the '56 F250 in the movie The Birds is an automatic.