I have the 3:56 diff from a '56 wagon in my Bird along with the standard (non-overdrive) 3-speed, and it's perfectly driveable around town and on any roads up to say 50 mph or so. Certainly easier than the original would be (which I think was 3:78) and my 312 has no trouble handling it. But even so I don't like to go more than 60-65 for any duration longer than a fairly short burst because I can't help feeling those rpms are taxing the old girl. I have to think a 3:89 mated to the 3-speed would be pretty uncomfortable for today's modern highway speeds, for any substantial length of time.

For those reasons I have long coveted the old overdrive tranny, even though it obviously wasn't the most ergonomic setup. It would be nice to have that option just for distance-highway cruising. I certainly wouldn't get rid of one if I had it. Just one man's opinion.

The 3:89 is to low for highway use. Thats one of the ratios that came with an overdrive. Keep the 3:30 with the standard 3speed. My tbird has a 3:89 and in high gear 1:1 is no good for hwy but great for side roads crusing around 40 mph.

-Gary Burnette-

Hey Rick; Would 3:89 gears be too low for hiway use with a 3 speed standard tranny?  I'm running a 292 in a 55 Fairlane. I also have on hand a 3:30 rear end from a automatic, would that be too high? I guess where I'm getting to is what would you suggest? I am real easy on my old ride so there won't be any abuse. I thank you for your time.

Anybody have a spare solinoid, I could use one?[/quote]





Billy,



I have a NOS 6V that I pirated some parts from, if that would be useful? I also have rebuilding instructions on my computer I could forward to anyone interested.

6 VOLTS/POS. GRD. NW INDIANA

I put a OD in my 56 sedan with a 3.89 rear end gear.  I used a $7.00 35 amp polastic case relay to power the solinoid.  Wired in the governor switch on the trans to the ground side of the relay coil.  This satisfies the reverse problem and also gives you the automatic pull out of the OD at low speeds.  I did wire in a OD shut off switch on the dash but it really is not needed.  Also used a repo kickdown switch but seldom use it because I have 3x2 on a 312 and the slam to the floor results in too much neck jerking. (when the wife is with me).  If I do want to switch out the od while driving 60 mph to pass a car, I let off the gas, throw the dash switch off and then hit the gas again.  I love the OD and plan on putting one in my 64 292 PU this summer.

POP

POP

I installed an overdrive unit on the tail end of a truck tranny and there was a rod which I had to drill the case for which would automatically disengage the overdrive if you put it in reverse. I don't know if all tranny's had this feature so as others mention above make sure it is disengaged before trying to back up. I also had to drill for the oil passages.

Anybody have a spare solinoid, I could use one?

55 Vicky & customline

58 Rack Dump, 55 F350 yard truck, 57 F100

59 & 61 P 400's, 58 F100 custom cab, 69 F100, 79 F150, 82 F600 ramp truck, 90 mustang conv 7 up, 94 Mustang, Should I continue?

I appreciate all of the replies and advice.  I think I'm going to wire it up with a simple switch first to get a feel for how it all works. 

A.J.

South Jersey

SMSgt USAF Retired 
1955 Ford Ranch Wagon & a couple of old guitars...Life's Good!

There is a reason the OD was automatic in operation. Manual shifting is demanding enough, without having to remember switch positions, etc. Forget once, and the OD is toast. I don't think my handle has been pulled for ten years, I am so used to the automatic/freewheeling system.



Just get a used or NOS relay and have it converted to solid state, repair the governor wires & kickdown switch, and you'll fall in love with the original system.

The increased engine life alone will pay for your trouble many times over, not to mention the improved gas millage.


6 VOLTS/POS. GRD. NW INDIANA

If your interested I have a regular 3 speed tranny (actually a couple of them) if you would like to swap trannys.The length of the trans that you need is important.

I"m in Balto Md. so not too far away.

On a related note,if anybody has the attachment pivit that goes on the O.D. arm and attachs to the cable-I need one. Not the O.D. arm that goes into the transmission, just the pivit that hooks to the cable.

Oldmics

I agree with those that say keep the OD and just power the solenoid.  It is very easy and  you can't keep the high amperage current out of the pass compartment, it is already there at the ignition switch.  Remember the ignition switch sees full generator output. 

So run a new 14Ga wire from the aux terminal on the ignition through a 30 amp fuse to an on/off switch under the dash.  A small pilot light to show that the solenoid is energized is very handy and then to the solenoid. Connect this power to the solenoid as shown on the schemetic above. The second wire is just a ground for the kickdown and you do not need to connect that to anything.  You still need the T handle also.

When you have the car running down the road at about 30 mph in 3rd,  push  the T handle in and then flip the switch.  Nothing will happen until you lift your foot off the gas then it will shift into OD. Your motor will love you. The important thing to remember with this set up  is that the OD is engaged until you turn the switch off. So as you slow down the OD stays engaged even if you come to a stop.  Starting in OD-first gear feels like starting in second,  so turn the switch off. Another thing is you probably can not reverse the car without first turning off the switch and pulling the T handle out.  The regular OD tranys have a link between reverse and the OD that should disengage the OD but if the link doesn't work you will break the OD.

Doug T

The Highlands, Louisville, Ky.