All Big Six Extra over drive?

Relates to all big sixes

Lazy JW

Staff member
I drove my 81 F-150 2WD with 300-6, T-18 and 2.75:1 9-inch rear for 60K+ over a 3 year period on my 88 mile round trip commute in northern Idaho; this was year 'round, winter, summer, any and all idling time, any and all town driving (very little) plus any hauling. 90% was running empty with just me and my lunchbox (BIG).

I documented every drop of fuel in and every mile driven.

Average: 19+ MPG.

This was NOT a one-time fillup, this was an actual average for the total time and miles.

It takes about X-amount of energy to push a brick through the air regardless of the gearing.

F-250 Restorer

Famous Member
There are some great auxiliary transmissions being used out there like Brownies and Spicer. I think the trick is understanding them and understanding how to install them.

Borg Warner made a few great over-drive trans (R 10, R 11) from the 30's to the early 70's. Ford put them in some of their trucks. They were a three speed manual, with a two speed planetary gear transmission attached to the rear. Guys take that planetary trans section and put it behind other transmissions. Figuring out the splines and adapters, etc., stops most people.

There is a good video on youtube called 'how to put any transmission behind any engine.' What the guy doesn't say is that he just happens to have a machine shop to use. Good luck.

FWIW: A project like I mentioned takes a considerable amount of money. Go with a simple OD trans.


Famous Member
E4OD (and therefore 4R100) and 5R110.

You can skate by with the AOD and its electronic decendents in light chassis where you don't have the power to break things but the first weak link is the input and the billet one piece input you buy to fix that weak link prevents you from having converter lockup.