Ford flathead overdrive transmission
- Thread starter Ziggster
- Start date
tubman
Well-known member
'49-early '51 Mercury with the B/W R10 overdrive. Not the strongest out there, but a very useful unit behind a flathead. Some folks "cheat" and simplify the electrical operation when installing them, but I find when installed properly (factory wiring with kickdown switch and relay) they are more functional, and less vulnerable to breakage. You might have to do a little "mixin' and matchin'" to come up with a proper clutch for the earlier engine (these Merc's used B&B pressure plates), but there has to be something that should work.
rotorwrench
Well-known member
The R10 was a product of the mid century cars. Most manufacturers used them in one form or another. The larger cars and pickups used the T85 transmission with the R11 overdrive. They were a heavier duty unit. Ford used them clear up to 1970.
tubman
Well-known member
I have a couple of T89's (a variety of the T85) with the R11. While they are more robust (they hold up well behind FE's), it would be very difficult to successfully mate one to an early flathead (which @Ziggster has). I am planning on running them initially behind an 8BA, and later moving up to an early hemi or a Rocket Olds. (I have the proper adapters.) Those early Merc transmissions are probably the easiest way to get an OD behind an early flathead. I had a good friend that ran one in a '34 coupe behind a built 59A. It was a slick setup, but requires more work on the center crossmember than I would be prepared to do.
I can see just about everything you would need except the "kickdown" switch. They are readily available. Actually, most parts are because so many manufacturers used them.
I can see just about everything you would need except the "kickdown" switch. They are readily available. Actually, most parts are because so many manufacturers used them.
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pistonbroke
Well-known member
The best thing about these OD's is they are 30% Where as the later mustang and S10 stuff is around half that . Still better but not as good as original.
What would be the recommended final drive ratio be considering today's highways and speeds? Planning on putting an R10 overdrive behind a 59A in a '46 Tudor.
rotorwrench
Well-known member
The Mercury unit from 1949 through early 51 will fit the half bell and work with the 46 clutch OK. Just use the 3 on the tree to shift. The 1946 rear axle is going to be problematic due to the closed drive. The Lincoln cars of the early & later post war had a closed drive Borg Warner overdrive but they are long units so a custom torque tube would be required. Changing to open drive can be done but it will require suspension and drive shaft work.
38 coupe
Well-known member
When running 28 to 29 inch tall tires I try to get a final gear ratio with overdrive ratio times axle ratio to end up between 2.75 and 3.00.
The Borg-Warner overdrive can be a wonder setup, but trying to fit one into a Ford or Mercury built before 1949 is going to involve a lot of torch or sawzall activity. The installation that involves the least cutting is splicing just the overdrive section into the back of the torque tube. Installing the complete transmission will require minor to huge surgery on your frame, depending in the chassis.
The fitment problems with Borg-Warner overdrives is one of the main reasons that Columbia two-speed overdrive axles are still popular for 32-48 Ford & Mercury, and 36-41 Lincoln-Zephyr cars.
The Borg-Warner overdrive can be a wonder setup, but trying to fit one into a Ford or Mercury built before 1949 is going to involve a lot of torch or sawzall activity. The installation that involves the least cutting is splicing just the overdrive section into the back of the torque tube. Installing the complete transmission will require minor to huge surgery on your frame, depending in the chassis.
The fitment problems with Borg-Warner overdrives is one of the main reasons that Columbia two-speed overdrive axles are still popular for 32-48 Ford & Mercury, and 36-41 Lincoln-Zephyr cars.
51504bat
Well-known member
Don't really know what you're working on but an option might be a Ford 3+1 o/d trans out of a mid '80's p/u. You would need an adapter from Model Engineering to bolt up the Ford toploader to the flathead. The 3+1 tranns are available with a top shifter which makes the install appear close to a stock shifter.There are some others from other applications that had a remote shifter that bolted onto the side of the trans. Just another option.
rotorwrench
Well-known member
That would be the T170 RTS TOD made for Ford by Tremec in Mexico. They are still out there but getting harder to source at local salvage yards. The best ones were made to fit behind the 302 and 351 Windsors in pickups & Broncos. Several shops set them up for Model As and later V8s with torque tubes back when they were plentiful but I think there is only one shop that may still do it.
235/65r 16 = 28.00 Dia. = 88 inches circumference = 720 revolutions per mile. At 70 miles per hour and ~2000 RPM would be about a 2.78 final drive, which would equate to about a 3.60 rear end gear.
