Truck Update #5: Transmission Swap Success

As I posted previously, my Ford 3.03 transmission was toasted. Between several bad syncros (causing a heck of a grinding noise), and the shifter being junk, I thought it best to swap in another transmission from the junkyard than trying to fix the old 3-speed.

I went to a local metal recycler and asked if I could look over what vehicles he had. To my surprise, he had at least 5 1970s Ford trucks to pull parts from. I asked him if he could pull a 1978 F-350 out so I could get the transmission out of it. We agreed on a price, and he pulled the truck out so I could get to work. It took around 2 hours, but pulling the transmission was not so bad.

What did I pull? I pulled the mighty New Process 435 4-speed transmission with the following gear ratios:

(The jump between 3rd and 4th kind of sucks. 3rd is too low to drive 25MPH, but 4th is too high!)

I also pulled the removable transmission tunnel, and the crossmember. It turns out that I did not need the crossmember, but the tunnel was a great find. I got the transmission home, started cleaning it up with a pressure washer and a wonderful degreaser called SuperClean, and set about installing it.

The next day, I pulled the truck into the shop, and had the old trans out in a few hours.

I cleaned up the inside of the new transmission as well, because I figured it has probably never been inspected. The old gear oil smelled awful, so I dumped it out, SuperCleaned the inside of the gearbox, dumped that out, then put conventional 90W gear oil in it.

I had difficulty getting the NP435 in my truck, but it was an issue of really bad luck which I’ll describe later. The only three things I had to change to make the NP fit were:

  1. Relocate the crossmember. Easily done with some drill bits.
  2. Swap rear yokes. The NP435 came with a larger yoke than the ujoint on my driveshaft could handle. Upon researching, I’m not sure the ujoint I would need even existed, so I robbed the smaller yoke off of the old 3.03. It fit the NP435 perfectly, and the driveshaft mated up to it just fine. Believe it or not, I did not need a longer or shorter driveshaft.
  3. Cut a great big hole in the floor! While I was very hesitant to get violent on my factory transmission tunnel, I had to because the NP435’s top plate and shifter are really tall. I just left enough metal for the new transmission tunnel to sit on and shot it down with some large self-tapping screws. It actually looks half decent.

So I swapped a junkyard transmission into my truck pretty cheap and without any huge hang-ups like I was expecting. The F-350 I pulled from was a dually RWD truck, and I think the NP435 from a 4x4 would have been a little more trouble, because I’m almost certain it has a different tail housing. But I did not need a longer driveshaft, or anything else expensive so I’m very pleased.

My Terrible Luck

I had the worst time actually inserting the transmission into the motor. At the time, I did not know why it was so bad; I was slamming and even kicking the transmission repeatedly to get it through the clutch disc. Eventually, it went in with some help from in the cab (through the hole in the floor). When I fired it up for the first time, I found out why: my clutch disc had frozen up to the flywheel! This was positively ridiculous: this never happens in such a short time. Heck it can take years for a clutch to stick to the flywheel. But I know that’s what happened, because the transmission made a grinding sound in every gear, and would take off like the clutch was already engaged! Later, I made some adjustments to my z-bar clutch linkage, and slammed the clutch pedal many, many times. It eventually freed up and works normally again.

Say No to Ethanol

Ethanol did something awful to my carburetor. If you did not know, ethanol attracts water when it has been sitting for a while. The truck had been sitting around 5 or 6 weeks, and apparently that was enough to gum up the carburetor. I think some junk in the carb was causing the motor to run extremely rich. It fouled my spark plugs, making starting even harder. I took the carb off and gave it a thorough cleaning.

Another thing about carburetors: for some reason or another, it seems like every time I have to open one up, when I put it back on the vehicle, it refuses to start. 99% of the time the needle and seats are stuck. Fix with a little violence: take a wrench or other bludgeoning tool and lightly tap the top of the carb around the needle and seat. It sounds stupid, but it works.

It Still Ran Like Trash

Despite cleaning the spark plugs with a brass brush and carb cleaner, and cleaning the carb itself, the truck still ran awful; most notably, it would not want to start back up after running. I fiddled with ignition timing and the carburetor but got nowhere. Then, I remembered how to “steam-clean” a motor.

Before I describe the process, I must caution anyone who wants to try this: you can hydrolock your motor if you do too much too fast, so err on the side of caution.

I got a small plastic bottle, made a small hole in the cap, and filled it with water, about 6 ounces. I turned the truck on, set the idle around 2000-2500 RPM (so the engine wouldn’t die), and slowly drip-fed the water into the carburetor, being careful not to add too much at a time. After it drank the whole bottle, I set the idle back to 850 RPM, and cut the truck off. Then, I tried starting it again, and it finally started like its supposed to.

Why does this work? The process is simpler than it seems: by adding a small amount of water into the engine’s combustion chambers, upon the combustion stroke, the water will become hot steam very quickly which will wash out any carbon residue from running bad gas or too rich. On the exhaust stroke, the steam will be evacuated with the exhaust gas. I proved this by checking spark plug #1 before the cleaning and after the cleaning: it was nearly fouled before, and a normal brownish color afterward.

Why do you need to be careful? This one fact: water is incompressible. You cannot “squeeze” water like you can air. So what do you think would happen in this situation: suppose we have a 100cc cylinder with 10cc at the top of the piston’s travel; what would happen if I poured 30cc of water into this cylinder? At best, the motor stops running and hopefully is not damaged, at worst, the motor bends a connecting rod which necessitates opening up the bottom end of the motor. So again, be careful!

Junkyard Treasures

Since the truck is finally moving again, I took it back to that salvage yard and got a few goodies. I bought a practically new truck tool box and a better set of side mirrors off of a 1975ish F-150 for $80 altogether. Everything cleaned up beautifully.

I hope the truck will finally give me a break from its abuse and my ignorance. My aggravation with it during just these two weeks has never been worse, but I can’t say I didn’t learn a few tricks. I may do a more detailed write-up on FTE, but at least theoretically, and minus my horrible luck, swapping out a 3 speed for a NP435 is a cheap and easy way to get rolling again. Who needs overdrive?