I would like to replace the standard top-loader 3 speed in my F-1 with a 3 or 4 speed overdrive (top shifter) transmission.


I want to keep the stock 3.93 rear gear so I can pull a trailer and the navigate hills in our area. The engine is out being rebuilt and now would be a great time to work on this upgrade.
Has anyone adapted a 3 or 4 speed OD trans to their 8RT flathead that could help we work through the choices and problems that I might encounter.


Thanks,

 

Any overdrive manual transmission you put in your truck that will stand up to towing a trailer will require you to cut your cross member. In fact, any overdrive manual transmission that can be used in your truck will require you to cut your cross member. How far from how Ford built your truck do you want to go?

 

I have a 5 speed (T5) trans in my F-1 behind the flatty. As said, quit a bit of modification is needed. Sure is fun to drive now though....

 

Chuck's Trucks has the OD transmission and the adapters to install it. The transmission is from a 1984 - 1987 Ford F150 with a 300 I6 or a 302 V8. Chuck will sell the parts separately if you want to get the transmission yourself or will sell you a complete kit including a rebuilt transmission. It all depends on your wallet. Give Chuck a call.

 

Good info, I will give Chuck's Truck's a call

 

RTS TS-OD Top Shift 4 Speed Overdrive. 300/302: 1984/89 F150, Bronco & E150. This trans is a notorious "weak sister."

The F150/Bronco shift lever is a convoluted rigamarole composed of an upper and lower section...including a nylon bushing that is notorious for cracking.

All the parts are obsolete, difficult to find NOS

 

I definitely would not shy away from this trans when installing on a stock flathead. It may be a "weak sister" to the earlier cast iron top loader but it is plenty strong enough to handle our 100HP flatheads. I wouldn't recommend it for a 300HP high performance motor though as it was not designed for that amount of horsepower. Also, there is a truck and a car version of this transmission with the truck version having larger input and output bearings. The rest of rebuildable internals (sycros, seals, etc) are the same between the two. There are 3 different overdrive ratios (27.6%, 37.6% and 41.1%) available as well.
As far as the shift handle is concerned, it is relatively easy to weld on one of our original shift handles onto the RTS shifter to eliminate the nylon bushings. It has the advantage of looking stock after installation. Chuck offers this service for a nominal fee.

 

Most people are unaware that there are two different versions of the 4 speed overdrive.

There is no car version of the RTS, cuz it was never installed in cars.

But the RUG SR-OD Single Rail 4 Speed Overdrive was...this trans is another "weak sister." One speed shift, you can kiss the little darlin' good bye.

RUG installed in misc 1977/83 200/250/255/302 cars, 1978/83 F100/150 300/302 2WD & E100/150 300/302/351W.

The RUG shift lever is one piece, fits into a nylon bushing (D9BZ-7K453-B) in the extension housing. Bushing is obsolete, only a few are available NOS. Northwest Transmissions also has it.

 

Roughly the same amount of work to put in either the SROD or a T5. T5 parts are everywhere, reasonable, and they are good for plenty of power (if you get a World Class model). S-10 tailhousings with the preferred shifter location are getting scarce, tho. And cost of a well-used T5 has gone up. But the gearing with a 5-sp and a stock rear end is much more friendly than a 3 + OD, although it can be argued that 1st in the S-10 T5's is near useless except for parades (4.01 ratio).

 

How about a BW t85/r11? Wouldn't that be less modification?

 

It's worse. Lots of electrical gizmos to source and hookup, and the OD solenoid falls right on the crossmember, right where the brake/clutch assembly is, so you'd have to go to hanging pedals and create new linkages.

 

I did about 80 hours of research on manual OD options to go with in a stock engine 48-50. After dozens of spec manuals, 3 threads with lots of help from NumberDummy, Ross and a ton of other people I ended up conceeding that T5 and cutting the crossmember really is the best option.

There's about 2 dozen links to tech items / references at the end of my page here:
Ford F1 series Transmissions swap

and throughout the page buried in the chart are links.

Do all the research you want, I think you will come to the same conclusion - T5 is the way to do it. (search on my name and you can find all the old threads too)

 

BRIAN!
Great source of information.
End of story for me, I will be able to service the t-5 for as long as I'm alive.....(hopefully for a long time)
Nice F1, great color.

 

The mounts that Chuck makes allow a bolt in overdrive for F-2 and larger trucks. No overdrive bolts into an F-1.

 

You wouldn't want to use the SROD as the shift lever sits much farther back than the RTS model.