The Stovebolt Site Forums The Shop Area Driveline overdrive, educate me

I see occasional posts on here regarding overdrive transmissions. Until now, I didn't know that Chevy ever offered overdrive. Was it an option, or did it come on only certain models. Was it a GM product, or did they buy them from Borg Warner? I have overdrive on my 1950 Studebaker, and love it. Can overdrive be added to our old transmissions, or is it a special tranny? I'm hoping that you guys can educate me regarding this. Thanks

There is a 3 speed OD transmission on Milwaukee Craigslist for $200

Overdrive transmissions have been around before WW2 as a means of improving gas mileage.
New 1955 trucks had the option of electronic-overdrive.
1956 U.S. Interstate Highway System was funded for higher speed travel.
From 1955-65 electronic overdrive transmission did not have synchros in 1st and 2nd gears.
1966-69(?) fully synchronized electronic-overdrive.
~1983 overdrive was incorporated into the gear set of a T-5 transmission for Chevrolet S10.

Short and sweet, the electronic overdrives are nice but expensive. Usually you find the transmission without the solenoid, kick down bracket, kick down relay, governor, pull handle for manual operation etc. Typically the electronic overdrive is used on restorations. There is a ton of information freely available (let us know) but most choose to go with the S-10 T-5 for the simplicity and readily available repair parts.

The Craigslist transmission is a 1955. It has the governor and solenoid.
Missing are the pull cable, relay, wiring harness, carburetor bracket and kick down switch.
The 3 speed gears are common with non-overdrive transmission gears.
The Borg Warner tail housing (R10H-1) if worn or damaged, can be hard to find repair parts.
Unless you live locally, shipping can be a bit expensive.

Mike:

I have a 3 speed overdrive in my 58 Suburban and love it. I really wanted to keep the three speed column shift. I'm kind of nostalgic. Now I get the best of both worlds. I keep the column shif and get some highway driveability. The swap was pretty easy. Finding a good unit with all the parts is the hard part. If you get one with a working governor and solenoid you are 90% of the way there. The other stuff is easily fabbed or replaced.

I have a long thread PM that I exchanged with another bolter on the subject. I'll dig it out and PM you when I get home. Too hard to do on the phone.

Larry

Overdrive transmissions were offered by Chevy in cars and light duty trucks beginning in 1955. They use the same case as the standard 3 speed Muncie with the exception of having a hole drilled in the housing to incorporate the reverse lock out/engagement lever. The overdrive portion and the adaptor plate were provided by Borg Warner and are specific to each manufacturer.
Generally, most of the internal components interchange with other R10 units. IE: Planetary, sun gear, ring gear, roller clutch, blocker ring, etc. The standard 3 speed is referred to as a SM318, the overdrive is a SM319 for the early years. The later unit, a Saganaw full syncro unit is a SM326 - R10Q, 1966-69.
Fred

Mike I don't see that one of your questions has been answered. You can not add overdrive to the AD transmission (nor any torque tube transmission). But you can add overdrive to a Saginaw 4 speed transmission with a bit of work and it makes for an interesting (however some think not all that practical) transmission. Given that the overdrive transmissions out there are over 50 years old now and all, the T5 (as others have mentioned) is a really good option. If you go with overdrive (or the T5), you will need to abandon the torque tube and stock differential. Good luck.

I had a '65 Impala (4-door hardtop) with what I presume was a stock overdrive. The extra gear ratio options when navigating the mountain roads of Wyoming...up and down...were nice.

I have been playing around with BW overdrives for 60 years and I still like to drive them. Chev SM 319 transmissions are around. I mostly played with Ford transmissions that use A BW T85, T86 or T89 front box behind either an R10 or R11 OD section. The BW front section is a lot tougher than the Muncie but hardly anyone drives like I did 60 years ago. The GM Saginaw is very similar to the BW front section. Some parts are interchangeable between the GM and other OD, but not all. The photo shows one GM solenoid and two Ford solenoids and they are noticeably different.

https://photos.app.goo.gl/Q6bbNYoFKrHeU3Ac7

I wire my overdrives like Ford no matter what the installation is. I like it much better than the wiring GM used.

Crenwelge;

You can't just throw out the comment on wiring without explanation! How are they different and why is the Ford way better?? I'm curios. I have to know. 😉

Larry

The only difference in a SM 318 transmission case and a 319 is one hole drilled for the lockout pin that disengages the OD when reverse is selected. With a very rigid drill press with no spindle run-out or a Bridgeport mill and a chucking reamer, it's possible to make a 318 case work with the B-W OD unit.
Jerry

Larry, Ford placed the kickdown switch under the accelerator while GM had it at the carburetor. They were hard to keep in adjustment.
The components do the same thing.

https://photos.app.goo.gl/AddGmkRxPng87YvS9

Jerry, The 318 without OD uses a different mainshaft than the 319 with OD.

Jerry didn't say there is or isn't a different mainshaft.

I thought I could figure out DC automotive electrics Kenneth, but this one has me baffled.

What is the purpose of the normally open contacts that connect the points side of the coil ( #18 Red-White stripe) to a set of normally open contacts of the overdrive solenoid ( #18 Blue-Orange stripe)? Looks to me like it would short points to ground when the overdrive solenoid was activated and the kickdown switch was pressed, causing the engine to stall momentarily .

You want to momentarily kill power to the engine so that the input torque to the transmission drops to nearly zero allowing the overdrive planetary lock pin to set properly without grinding and slipping over its home position
As soon as the overdrive is fully engaged power is returned to the engine
If all works well you barely notice the momentary subsecond engine cutout.
-s

Makes perfect sense.

I guess it could possibly cause a tailpipe backfire, but knowing Crenwelge's history, he would probably like that.

In a previous post, the solenoid pictured on the left is not GM, it is for a 68 up Ford unit. The others were used on earlier Ford, Chevy, Studebaker, Rambler, Willys, and others with a 1" shaft extension. The GM R10Q solenoid is somewhat different as it has a smaller center boss and a 1 1/2" shaft.
Fred

The ignition short is so quick that it won't cause a backfire. As the torque on the input shaft unloads, power is lost to the solenoid pin, and the spring retracts it. Once that happens, power goes back onto the ignition system, and the engine restarts. It all happens in a fraction of a second. There's lots of good engineering involved in the setup, and people who choose to replace it with a toggle switch obviously don't understand how it's supposed to work.
Jerry

I agree with Jerry. The design is brilliant. My challenge was that my later model 250 has HEI ignition. There isn't anywhere for that wire to attach. I have it taped off under the hood. My other issue was no matter how long I stared at the carb and thought about it, I couldn't find a way to attach the bracket and switch to the carb. I ended up mounting the switch in a hole in the dash left when I removed the factory radio. To go back to direct drive I let off the gas while I punch the switch by hand, wait a second and get back on the gas. Drops out of OD no problem. It's kind of "country" but it works great. I use the OD constantly when driving around town. 2nd gear in OD is perfect for cruising around. As long as I'm not on a hill I can slip the clutch a little and take off in 2nd. Get up to speed (+/- 25mph) let off the gas, push in the clutch, let it out and I'm in OD. I drive it like a 2 speed trans. Using the clutch for OD isn't necessary but I feel like it cuts down on ware and tare.

If you're running a GM HEI distributor, grounding the "tach" terminal in the cap beside the power input wire will short out the ignition. If you're not running an HEI, you're about to have more problems than an overdrive can solve! A micro-switch with "normally open" and "normally closed" contracts mounted under the gas pedal will replace the kickdown switch.
Jerry

I prefer a kickdown switch, but back in the 1970's they were almost impossible to find. A toggle switch will work if you drive it like a two speed axle. You flip the switch and momentarily let of of the gas before you step down on it and the OD will shift just as smoothly as with a kickdown switch. I started driving trucks with two speed axles over 60 years ago and put over a million miles driving a two speed Eaton or a 3 speed Eaton which is actually two 2 speeds running one in high range and the other in low to get an intermediate speed. Using the clutch allows them to be free for too long and this is what tears up two speeds as well as overdrives. Now kickdown switches are being reproduced and can be bought for around $30. So I would no longer recommend using a toggle switch.

Did they make an OD on an 4 speed manual? I doubt mine has it but it'd be nice to just discover another gear

I had a Toyota Landcruiser '84 that had a "Ranger" overdrive. Totally mechanical. It mounted in back of the trans, it got the low geared car useable at highway speeds. I haven't looked it up. It seems like it would be easy to mount a gearbox behind the trans on a simple two wheel drive truck with a little bracket, simple shift linkage and drive shaft resectioning. Ideas anyone??

Turn a small 3 speed like a Chevy passenger car torque tube trans backwards and bracket it into the driveline behind the main trans. Use an electric solenoid or a vacuum setup to shift it between 2nd. and 3rd gear. 2nd. will be OD and 3rd. will be direct drive. Both gears will be synchronized.
Jerry

This is worth looking into. I will! Makes total sense.

Running the gears backwards can be a bit noisy. I've driven 3-speed auxiliary transmissions on big rigs that made a racket, but they pulled well for untold thousands of miles. Mount the second transmission in rubber-cushioned crossmembers to isolate most of the noise.
Jerry

Well...after looking at this for a while, I don't think it's worth experimenting.

I'm going the other direction- - - -building a doodlebug tractor with a Mercruiser 4 cylinder, a Turbo 350 automatic trans, a crash box 4 speed, and a vacuum shift 2 speed rear axle. It will have 24 speeds, ranging from SLOW to REALLY SLOW

Install the crash box backwards and it'll range from SLOW to TOO FAST FOR A SANE PERSON TO GO.

Yep, for sure- - - -especially with 24" rear wheels for a Farmall Cub!
Jerry

Larry 58 burb In 1967 my first AD truck 283 2x4 was overdrive,I never used a kickdown switch,had the kickdown on the dash. Put tension on the driveline,punch the button would downshift very gently pass another vehicle let up slip right back in OD. You don't want to open your 2-fours to downshift. If you get on it best to put it in direct mechanically. I ran the wheels off of that truck,drove it 70 mile round trip daily,gas war price was .17 cents. They act like the wiring harness is such a battle,any older auto repair manuel has the diagram it's about 3 wires. On the 4-speed saginaw over drive,built one of those in about 1970 worked fine. there is one in my 52 3600 out there inthe shed right now. Also had an overdrive unit built at home that went in like a brownie with 2 yokes ran the wheels off of it too !!

Bill Hanlon Overdrive malfunction will demolish the muffler just like turning the key off then back on.

I still have an OD on the back of a Dana 18 transfer case.

Ed