Hot Rod Forum : Hotrodders Bulletin Board

Hot Rod Forum : Hotrodders Bulletin Board (
-   Transmission - Rearend (
-   -   Overdrive transmission (

merkery 06-18-2002 10:28 AM

Overdrive transmission
I have a flathead jack 3/4 race 8aba flathead that I just finished building for my 1951 mercury custom. I have the origonal overdrive transmission in the car. The person I bought the car from had disconnected and abandoned all of the overdrive components, so the car was out of overdrive when ever I drove it. On the freeway it sounded like it was going to grenade on me. I have found all of the missing parts from Mr. Merc. I will be installing all of the parts soon. Problem is...Nobody can tell me how to engage, and disengage the overdrive. There is a kickdown switch under the gas pedal, a relay on the firewall, a pull handle under the dash, and a governor on the trans. When do I pull the handle, and when do I push it in. Is there a simpler way to do this?

scumdog 06-25-2002 09:25 PM

Hi, Scumdog from New Zealand here - hope I can help you about the o'drive, I had one in my Mk2 Zephyr and it is the same principle as yours.
From memory if you pull the dash cable to put it in overdrive the o'drive will work once you are faster than a given speed, i.e. 35mph. To engage it you wind up to above that speed (with the dash cable pulled - it may be vice-versa in your case) and take yor foot off the gas pedal, the overdrive will now engage and give you long legs - some o'drives only work in 2nd and top gear.
When you want to pass a car on the freeway you mash the pedal to the floor for a split second and the o'drive drops out and you are into direct drive for acceleration. (the switch on the floor "kills" your ignition spark for a second taking the load off the motor enabling the solenoid to pull the 'box out of overdrive)- after you finished passing just take your foot off the gas and viola! you are back into o'drive!
The great thing I found with the o'drive was that you could leave it engaged 99% of the time and below about 10mph you could pull into low gear without using the clutch as the o'drive is fitted with a sprag (one-way) clutch, very handy when you have a non-synchro first gear.
The o'drive has a mechanical lock-out so it does not work in reverse or you would screw it up big-time. Hope this helps, Cheers, Scumdog

All times are GMT -6. The time now is 11:43 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.0 PL2
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2017 DragonByte Technologies Ltd.
Copyright 1999 - 2012. All Rights Reserved.