adding overdrive .......

[mcrews]

Gear Vendors under/overdrive transmissions the most awarded auxiliary transmissions.
saw on of these at a hotrod shop last week

imagine a 22% reduction in rpms w/ the flick of a switch!!!!

couse only gm ford.....

I know this is not for your run of the mill 3 cylinder ecobx, but could really help those who have to have the truck.

[Old Tele man]

...back in the 1950's "add-on" overdrive units were very popular. Most mounted in the tailend extension of normal 3- and 4-speed manual transmissions. Some were manually engaged, others electronically.

...I had one on my 1953 flathead Ford with later-1955 3-speed transmission.

[Frank Lee]

I looked at getting GV OD once. Number one, look at the COST!!!

Then math out the potential reduced fuel use incl. annual miles driven vs cost.

Unless you put on uber miles/year, it just doesn't work.

The other thing I don't like about add-on OD is, it's another gearset in the drivetrain, which actually reduces drivetrain efficiency as far as internal friction. The only reason it works at all is that the benefits of reduced engine rpms more than offset the increased friction disadvantage. To that I say, unless the vehicle is so heavily loaded that it needs 8+ forwards gears, one is better off getting their top cruise gear lowered via regular transmission or lower rear end ratio or both.

[Big Dave]

I have one. It works - good for 1.5 MPG. I am a big-mileage driver and can live with the cost.

I'd rather have 2.56:1 gears but they just don't make 'em for Sterling 10.25s.

[Old Tele man]

...a possible "alternative" to an "add-on" overdrive is simply changing the gearset, which is "possible" in many different manual gear boxes (but NOT all).

...this is possible, because the same transmission might have one set of gearset for USA and a different gearset for European models...search the factory service manuals to see what (if any) possible gearsets are available.