First, let me start out by saying I am not a professional mechanic nor do I claim to be an expert on transmissions. Back in my racing days, I rebuilt a few transmissions out of necessity. I rebuilt a T10 once and incredible as it may seem it actually worked afterward. My current Ford is most likely the last old car I will ever own. It's a culmination of all the things I always wanted when I was young; a 50s Ford, Y block engine, manual transmission and hot rod engine. I bought this 55 TBird because it was a rust free west Texas car and it had a manual transmission. To my delight, it also turned out to be an Overdrive car because I had always heard Overdrive cars were faster, but I didn't know why.
When I first drove my TBird, I was confused about this transmission. It freewheeled when decelerating without engine braking. I didn't like this as it was different than the 4 speeds I was used to. I actually thought it was broken. After reading more about it, I learned this is normal. Once I figured out how O/D worked and how to drive it, I was hooked.
Ford O/D was a wonderful idea years ahead of it's time. It allows the use of numerically lower rear gears without the disadvantages. I'm not sure what rear gear is in my TBird. People tell me it's either a 3.89 or a 4.11. It takes off like a rocket running about 3,000 rpm at 60 mph in third gear. I lift the gas pedal and it shifts into O/D and the tach drops to about 2,200 rpm. It cruises along quiet and happy until I kick it out of O/D then the car changes personality. I love it!!
Recently, my O/D stopped working. This scared the heck out of me because I just had the tranny out for an engine rebuild. A 55 TBird has a tiny transmission tunnel. The Ford T86 O/D transmission in my car barely fits. In order to remove the transmission without removing the engine, you have to remove the bell housing with it. Let's just say it's an experience you don't want to repeat too often. I read everything I could find and started to troubleshoot the problem. The mechanical O/D itself is actually pretty simple. The wiring is not hard to access, but was difficult for me to understand at first. The hardest part to access is the governor. It's at the rear of the transmission buried behind the frame. If this part goes bad in a TBird, you most likely will have to take the transmission out. All the governor does is ground the O/D circuit when the car reaches a certain speed. I made a long wire with a 12 volt light at the end. I lifted the car off the ground, connected the wire and light from the battery to the governor and started the motor. Somewhere around 30 mph, the light went on. As soon as I dropped below that speed it went off. Hallelujah! The governor was working.
Eventually I found the problem. One of my electrical connections was not making contact. I learned a lot about my O/D in the process. There are only a few simple components to this system. The experts say most of the problems are wiring. It was in my case. I thought I would post my experience so someone else may benefit. Old Fords are fun!!
