I doubt if the Napa fluid is causing the problem but it is the wrong fluid. Even if you drain it and put in Dexron II I don't know how you would drain the torque converter which probably holds 2 quarts. The whole system probably holds about 14 quarts.
You may want to call Joseph Industries in Ohio, tell them what you did and they can advise whether to drain the fluid.
There should be an oval plate riveted to the top of the transmission with the part #. It should start with 9020 or A9020.

Thanks duodeluxe, it is great to have you provide your knowledge and expertise.

I refilled the transmission with Napa tractor & transmission fluid, it says that it meets a number of specs but Dextron II is not one of them. I am not sure why I selected this product but do you think that this could be my issue? (low power to wheels)

The Master Cyl that I put in my truck fit and worked but I remember having to almost eyeball the thing. As I recall it looked correct and had the correct bolt spacing so I went with it but I wonder if there are similar (interchangeable) cylinders with different bore sizes out there and maybe the one I chose is undersized. I often think that all my break issues would go away if the Master would just pump more fluid. Any thoughts? Cheers

The transmission and differential utilize the same sump and the fluid is Dexron II.
The military version of this model is totally different from those sold to industry through dealers.
I'm just guessing but I think the Baker part #'s are:
9025FY1 Master cylinder
119031 Brake shoes
103150 Wheel cylinder
103151 Wheel cylinder.
Forklift truck brake drums should not be turned. They don't go fast enough to wear the drums. The reason that brakes fail is that they become oi or brake fluid soaked.

Duodeluxe, you have posted serial numbers for a Baker Master Cylinder in the past. In that case the PN was 100830 for a FMD30/40 or 50. Do you know if that is the same PN for a FJF-040? They look similar.

BTW, I think I found TM-10-3930-623-34P to be the most useful manual for part numbers on this truck. Not everything was the same as mine but the brake parts were.

Yes, Burns in Long Beach

I am thinking I got the Master Cyl off eBay. I know what I installed looks a lot like this part (ebay part number 371855156204) but I don't recall the reference to Harley Davidson but that is what the part I got looks like. I recall that they mentioned the bold spacing and that made me pick it.

Keep in mind that I was disappointed with the stroke of my system and I wish the master had just a bit more volume than the part I purchased so maybe I got it wrong. If you find something you think is a real winner, please post a reply with the info.

Is it Berns in Long Beach?

The part numbers I purchsed from Burns was

Wheel Cylinder 121FD19606 and 121FD19607
Seal (2) 061A1805B340
Shoe (4) 9993722Y285 (there is a core charge for these)

I don't recall where I got the master from but the PN I have from the parts manual is F2796. The national stock number is 2530-00-495-8860 in case that helps. As I recall I was never able to match the exact number but had to chose from parts that looked the same at the old one and selected the correct bolt spacing. Hope this helps. Let me know if you keep striking out.

Thanks for the advice duodeluxe. I will give it a try. I think that the ATF that fills the transmission is connected to the differential. I do not see that these are filled separately although there is a plug on the top of the differential. I mention this only to suggest that I should recheck the ATF level in case this fluid redistributed in the system and the transmission is now low. I will take a look.

I also did replace the carburetor so your suggestion about the carb could also be spot on. Sound like I should not sell the old girl quite yet :)

You wouldn't happen to have the part#'s for the brake mastercylinder, brake shoes and seals do you? My military TM doesn't have the part #'s in it.

Not climbing your driveway is not related to how the forklift truck was ordered.There are a few reasons why yours won't climb the driveway. Obviously first check the Trans fluid level, even if it is 2 quarts low that would create a problem.
If it's full then put the forks against a concrete wall, put it in forward and accelerate the engine to full RPM's. The tires should spin. If while doing this test the engine bogs down then either the timing is not set right or the fuel system needs adjusting. If the tires don't spin and the engine doesn't lose power, the issue is either that the inching valve isn't set correctly or the transmission is worn.
BTW- The brakes are self adjusting.

Thank you for your knowledge. My forklift is also a military one but since I'm on flat ground it works for me. Thank you again for your response

Boy I put a lot of work into this old Baker. I loved it though. I did figure out the brakes, sort of. In the end I was able to get the brakes to work well enough to get down the hill of my driveway (not much extra margin) but then I hit my next problem, the forklift won't go back up! It only has a forward/reverse and not a high/low lever. Apparently, the military purchased a number in this configuration intending that they be used on level ground. My forklift won't climb much of a hill so I am going to have to sell it. I am super disappointed!!! Want to buy a forklift :)

For all those doing Brakes on a Baker FJF-040, here is what worked the best for me.

There is no external adjustment. You need to take off the entire drum assembly by splitting the gear reduction housing (halfway between the drum and differential. This will drain a good amount of AT fluid so be prepared. One big pain is the nut on the parking brake shaft located on the back side of the housing. I used a stubby 3/4 wrench and lot of patience to get this done. Keep in mind that in order to learn what I know now, I had to do this process 3 times on each side. Yes 3 times at about 4-6 hour a side. Hopefully you will only need to do this once per side.

Once the housing bolts are out (leave one in loose at the top) I used a jack to slowly apply upward pressure on outermost portion of the hub to split the seal. Removing the large backing nut that you will see inside this assembly, allows you to pull out the drive shaft/hub/drum assembly. Now you can access the shoes, etc. There is an adjuster (friction, adjust with hammer) inside as well but in my case, one of the seals was leaking so I needed to replace the shoes not just adjust them.

Once off I used a rotary wheel (grit covered brillo pad??) in my drill press to take of all oxidation on the inside of the drum even where the shoe does not contact. This is so you can slip the shoes back in as tightly as possible. Reassemble the shoes at tight as you can. You will not be able to turn the drum by hand and that is okay. Re-attach everything (the nut on the parking brake shaft may need to be reinstalled before the housing bolts are fully tightened). Bleed the brakes (I replaced all of my lines, master and slaves). It is possible that there is air trapped at the top end of the lines, so I also bled the lines by loosening a fitting at the Tee. Even after all this the bottom end of the brake pedal was softer than I wanted. It was breaking fine on flats but hills were an issue. In the end I have lost all respect for the guy that designed these brakes and I think the bore on the master cylinder needs to be a size larger.

I purchased the slave cylinders, shoes and seals from The Burns Company. I think these were referenced by the PN from the military docs. As I recall, I spoke with them and they were very knowledgeable. They had stock; prices were fair. Would definitely recommend. I purchased a parking brake return spring from McMaster Carr (96605K34). I also purchased some O-rings from McMaster for the shaft seal on the parking brake. Not sure which one ended up fitting best. Lastly, from McMaster you can get the felt seal strip (PN 8762K811) that goes on the housing and seals to the drum. Cut to length. It worked well.

I also did EVERYTHING else on this truck (new carb, fuel pump, fluids, filters. Flushed the cooling system, replaced hoses. Plus, many other little things. I really like this truck (hate the brakes). I am sad that I can't use it and have to let it go. Good luck!

Did you ever figure this out? I have a 1973 same model and wanted to do the entire brake job. Where did you obtain your parts? I have the old military service manual as well.

Thanks Duodeluxe for the reply. I have done all of the items you indicated. Wow! That is the most work I have had to put into a brake job. Everything is replaced from the master on down. Master cyl, all tubes, slaves, seals and shoes.

These brakes have an adjuster that can only be adjusted by opening up the whole brake chamber (all of the work you noted). I see no place for external adjustment. If I tighten up the shoes and much as I can and put the drum back on, for some reason I cannot get enough brake pressure to get the brakes to work. I can get them to tighten enough where I can't spin them by hand but that is not enough and the peddle never goes solid. I bled the system of air. It is almost as though I can't pump enough fluid with the master to press the shoes solid.

If anyone knows of a trick i missed or a secret adjustment method. Maybe there is a secret air reservoir that regular bleeding will not get to and I need to vacuum bleed these. Thanks.

You have to remove all of the bolts (nuts) on the back side. That should the back side of the axle shaft. Remove the nut and Pound on the end of the axle shaft with a block of wood and that will separate the assembly to expose the brakes.
The red fluid is ATF which you will need to refill once you've completed the brake job. Replace all of the brake parts including the 2 big
O rings.