The Stovebolt Site Forums The Shop Area Driveline Overdrive Now Fully Functional!

My 3-speed with overdrive now operates as God intended! There are already several threads regarding how to wire overdrive. However, I thought I would share what I've just learned, to hopefully aid others who want the automatic overdrive functionality. I may break this into several smaller posts, for readability and clarity.

I bought my '61 Apache last year...my wife and daughters call it " 'Mater Jr.".

It has a Jasper crate engine with an aftermarket Carter YF carb. It appears that when the engine swap occurred, the original bracket and kickdown switch would not fit the new carb, so the owner never bothered to reconnect the overdrive. The gentleman I bought the truck from had installed an overdrive relay, but no kickdown switch.

Since an original switch wouldn't fit anyway, I made a bracket and switch by using two SPDT micro-switches. I mounted this to the Carter YF, so that at full-throttle, the switches are engaged by the throttle linkage. I went with a carb-mounted switch rather than an under-the-pedal switch because: a) carb-mounted is most like the original, b) I didn't want to drill a hole through the floorboard, and c) I didn't want the switch where a floor-mat or other object could get caught and possibly interfere with operation.

I did my homework; there are numerous wiring diagrams on the web, but some of them are unclear, misleading, or downright wrong. One pole of the switch is normally-closed, which allows power to the overdrive relay. The other pole is normally-open, which is connected between the overdrive solenoid and the negative side of the ignition coil. At full throttle, the switch engages...one pole removes power from the overdrive relay, and the other pole grounds the ignition coil through the overdrive soleoid, which momentarily impedes the spark and creates a 'torque pause', allowing the overdrive to mechanically disengage. When the overdrive solenoid is disengaged, the path to ground is broken internally, and ignition coil function is restored. This whole process is very quick, and feels just like kicking into 'passing gear' on an automatic transmission.

On the test drive, when I tried to engage the kickdown function, the ignition would lose spark as long as I had the pedal pressed...the solenoid would never break the ground circuit. The full-throttle loss of spark would occur even when overdrive was not engaged, which shouldn't happen at all. I immediately suspected that the solenoid was internally grounded.

I uninstalled the solenoid, and removed the cover. I found this oily fibrous mass inside the cover, as well as other fibers inside the backing plate. I'd read that there was supposed to be a leather insulator inside the solenoid, so I suspected that's what I was looking at. I removed the backing plate, and found more fibers. There were two rivets where the insulator had been attached to the plate.

On the attached solenoid diagram, the location of that insulator is the red line. The relevant ignition ground contacts are circled in red.

I removed the rivets, and cleaned away all the old insulator material. I took some measurements of the hole pattern, and estimated the insulator thickness at less than 1/8". I then 3D-modeled a new insulator, and 3D-printed a new one in a flexible rubber-like material that is petroleum- and chemical-resistant. I installed the new insulator with some small rivets, and reassembled and reinstalled the solenoid.

Success!

The replacement plunger insulator works perfectly. The overdrive system kicks in and out as intended. Last night, I gave the wife and one daughter their first lesson with the overdrive. I guess a family that shifts together sticks together.

-Kevin

Nice!

Nice to hear such a clear and concise overdrive function description and explanation.
Nice you were able to trace down the trouble accurately and remedy it.
I’d guess there are overdrives scrapped unnecessarily over similar situations!
I once put an extra manual interruptor switch to the solenoid on an old Plymouth, so that I could “downshift” with a slight lifting of the foot feed. Seemed so much calmer than the “flooring it”move! I love overdrives!

You done good! The only overdrive I ever operated was in an early 50s Ford car which was mechanical, operated like a 2 speed differential, but the control was mounted under the dash.

I often find joy in making the original technology work as intended!

Impressive, using modern 3D technology to reproduce long-gone and no longer produced material, cool. Thumbs up for sharing.

I wasn't as adept as Shakey61, I just used a pair of scissors and sound deadening material from my toolbox drawer, works like a charm.

Good show! Most overdrives will also "freewheel" before the governor comes up to speed, allowing you to make a 1-2 shift by simply easing up on the throttle and shifting, without using the clutch. Sometimes, even a 2-3 shift can be accomplished that way, depending on what speed the governor kicks in.
Jerry

LOVE my BW overdrive! Joy to drive. Makes me smile every time it effortlessly slides into OD.

I learned to drive in an old '55 Chevy sedan with a 235, and three-on-the-tree with overdrive. I have a special affinity for that setup. Every time I drive my stovebolt, I feel like I'm 16 again, driving around Grandpa's cow pasture.

-Kevin

I put an overdrive trans in my 51 behind a 235. I absolutely love it. 2250rpm @ 70 mph. Instead of a full throttle switch, I used a dash mounted toggle to interrupt the relay ground wire from the governor. Tun switch off, lift throttle and that’s how I gear down for passing or hill climbing. I live in the mountains so I wanted that option instead of wide open throttle.

Thanks for the "report", Sludgeburner.

You might as well "fully identify" your truck-set-up:

"overdrive trans in my 51 behind a 235"
what make/model/year overdrive transmission?

1951 truck
what make/model/size?

235 engine
what year and original "application" (car/truck and what model-vehicle)?

Thanks

I set mine up with a small pull on push off switch next to the lockout cable. I still use the governor so with the cable in and the switch pulled “on” the system activates just like it should and when you slow down it automatically pops back out. If i want to manually down shift it i just push the switch off and blip the pedal and its goes back in direct drive pretty instant. Im 100% happy with it. I dont think a WOT switch would be good in my application with the LS because it would be a little too harsh. I dont really ever floor it. 1/4 throttle is all it ever needs to get up and go quickly.

Sorry. Truck is 1951 3100 5 window. Not exactly sure about the trans mission year, but it is a 318 with r10 overdrive. Transmission has no pad for a mount if that helps. Engine is a 1960 full pressure 235. I have installed FITech fuel injection on a clifford intake. Distributor has been modified with a reluctor wheel and a magnetic pickup to allow the FITech to control the timing. Has an original set of Fenton exhaust manifolds.

Shakey 61 Great overdrive 'family ' story my first one was ferd but soon swiched,learned to put the switch on the shifter ball so I would,nt have to open dual 4 barrels to downshift. With tension on the driveline would shift down (like to pass) then let-up to go right back in o.d. worked very well. If gonna get on it go to direct.