Very interesting post,if I am remembering correctly Ford trucks that used a Mazda transmission used dexron the transmission.

Ford Rangers used to have a variant of the KM145. Are those what you are thinking of?

Eddy, are you recommending that I flush out the gear oil and fill it with dextron as a remedy for my current problem?

I'm not saying ATF wont do the job, however all my reading says the stuff doesn't meet the specs to properly lubricate this type of tranny. I'm open to some more info and some technical proof. However, in OP's case, its too late. Once that bearing is bad, thinner fluid wont do anything. Heck thicker fluid cant save it either.

OP... what's the mileage on this transmission. Your signature says over 300k, on the original tranny? That would be impressive.

I do see why the auto swap, especially with the lockup torque converter is the way to go for reliability... However I cant drive auto, hence can say this... You can get a kormex rebuilt tranny shipped for 750. I say thats a steal when local shops want more and this is a fragile tranny so I wouldnt trust just any dude to fix it. You can also try to change the input bearing. Miller Specialty makes a tool for the job. Worth a shot if you can get your hands on it, as buying it costs 200$ There is also a trick using two screw drivers to change it.

I was thinking in F150, may be wrong. Old age you know.

I don't know if this is the original transmission or not. This week I'm going to check the fluid levels and see how it looks. I don't drive it a lot. I've looked for other KM145's to drop in (would be a lot faster) but haven't found any. The auto swap sounds attractive, if I could find a donor vehicle.

I'm also forever poor, so even the cheapest things are painful! I'm hoping I can find a parts truck cheap and just swap it. We'll see how it goes.

Oh, and I have no idea if this is the original transmission. I bought the truck with 333K on it over 2 years ago.

Rangers and Exploders both used two different m/t's. One was a km145 variant and the other was a Mazda tranny. I know the Maz box used dexron, not sure about the Mitsu tranny. Both may have been used in other light duty applications by Ford with the 4.0 v6 or the 3.0 maz v6 engines

X2 on the Dextron in the trans, we once drained an old KM145 way back and it was full of ATF. IIRC that truck had a bunch of miles as well, over the years it seems the guys with the most miles on a KM145 were running Dextron.

That said these transmissions are made out of butter.

You have to remember the tranny was designed for approx 100ftlbs of torque in a sub 2500lb car, not a truck weighting a lot more with almost 50 more ftlbs. It is marginal in our application.

I think you're confused about this transmission. The KM/FM145 is a solid transmission. It's all about maintenance. The FM145/46 was the higher end option for the Ford Ranger and was offered behind the V6 engine options. The Toyo Kogo/Mazda Tranny was a hot mess and was typically used on 4cyl engines. The FM145/46 has a decent reputation among Ranger owners when properly maintained. Much like the FM145, the KM145 is a ball bearing transmission. If you do not take care of those ball bearings they will develop flat spots. It is important that you change the fluid every 30-40K miles. A transmission that has roller bearings are less prone to flat spots when neglected but I recommend properly maintaining your transmission no matter what your vehicle.

Like you had mentioned ATF is recommended for these transmissions because they have difficulty shifting when cold. I would recommend Mercon ATF.