The Stovebolt Site Forums The Shop Area Engine Shop seeking 3 spd. with overdrive information!!

I am very seriously considering installing a 3 speed with overdrive manual trans. in the frame off rebuild of my '71 Chevy stepside. It currently has the stock 250 c.i. with the 3 spd manual trans. I have located an o/d trans. , but does anyone know how they work, I mean, are the later o/d trans. electric and cable operated? Can anyone give me a brief "Overdrive for Dummies" course? Any help is appreciated.

Thanks, Bob

Welcome to the 'Bolt, Bob! This would probably be the most thourough explanation on how they work. http://chevy.tocmp.com/1955truck2shop/55ctsm0715.htm You will need to do some adapting, like installing a relay for operation of the solendoid. Try using the "Search" feature on this site, there's been many threads on just this subject, with lots of good info.

Bob,
The OD trans that you would probably want to put in your 71 would be a Saganaw which has a 1st gear syncro. It looks different from the early tranmissions as it has a 7 bolt side cover, the early ones have a 4 bolt side cover and are not syncro in 1st. They all use the same electrical/mechanical operating components.
Fred

Bill & Fred, Thanks for the information. I've read that I might need to modify my transmission linkage rods to get everything working. My current trans. is a Saginaw 3 spd. and I plan on going with the Saginaw with o/d. Do you think I will have to make mods. on the linkage? What about the driveshaft?

Thanks again!

Bob,
No problem with the driveshaft, trans length should be the same. Should also be able to use your existing shift arms from your old trans.
Fred

Hi just wondering how the tranny project is going? I have a 56 3100 with the 3 speed and was thinking of trying the same swap. I have the 390 rear end and I don't know what that will do to my over all crusing RPM? Now going 60mph sounds like the old V8 is running 3000 or better RPM. Would like to drop that 1000 rpm or so.

Roger,
In my opinion, the OD swap is the best thing you can do for these old trucks. The OD is .70, so with a 390:1 rear end you end up with a 273:1 final drive ratio. This will reduce your RPM's considerably. I run mine on the So Cal freeways with the crazies all the time. You also might want to think about upgrading to disc brakes though.
Fred

Please let me know how your project comes together. I've been looking for an O/D set up for my 64' C10, no luck as yet, but got to get the RPM's down at highway speeds.
DJ