Rebuilding and Installing a "1939" Transmission - Part 3

One piece of advice I got was to consider replacing the clutch while I was replacing the transmission. I hadn't noticed any problems with the clutch, and had only put about 5,000 miles or less on the truck since buying it, but I made a phone call to someone who had helped the previous owner build the truck. I explained that I was getting ready to put in a rebuilt transmission. He wasn't sure if the clutch had been replaced or not, but when I said I was disappointed that the transmission I had rebuilt had older gears inside it, I lucked out: he had a 1939 transmission in his garage that he didn't need it, and I could come over and pick it up as well as a spare set of gears.

This was a proverbial "offer I couldn't refuse". Chet has a very nice 1935 pickup himself that he bought a couple years ago from someone in Colorado. He was in the middle of rebuilding it yet again: he wasn't satisfied with the something about the gas tank and the rear end. I wish I had half his energy and experience!

From the right side, this looked almost exactly like the transmission we had just rebuilt. The shifter housing is painted black, instead of green, and it looks like someone had bent the shift lever to be lower. They must have had bucket seats because I think it would hit the bench seat in our truck.
The other side doesn't look so good: the case had been sitting in water had has heavy rust by the rear and by the clutch release shaft. This is a later model which uses a different clutch linkage and also happens to let the clutch fork rotate out of the way.

Some more details of the rust. Luckily, I wasn't planning to use the case. There's plenty of good metal there, but a lot of pitting.

The inside was much more satisfying: 1939 gears, or at least a gear set with a new synchronizer with blocking rings So all we had to do was transplant the gears from this case to the case we had bought and repainted.

I've finally got around to writing this down nearly two years later and don't remember much about taking it apart, so it must have gone fairly smoothly. I did take a few more detail pictures like this of the reverse idler gear to make sure I could put the parts back in the proper orientation. I must have had some problems getting the main shaft out, but don't remember whether I removed the synchronizer first, or managed to get the rear bearing to come loose.

We were able to get the new bearings off the old transmission okay by driving the shaft through while supporting the bearing in something. And heated the bearings in a relatively cool oven (250 degrees) to get them to slip onto the shafts. The real fun began when trying to get the new gears back in the old case.We tried the slide forwards-then-backwards dance, and the output shaft just wouldn't go far enough forward to let the rear bearing slip in.

These pictures actually shows the older gears still, but with either set of gears, the result was the same: the cluster gear blocked enough of the front opening to prevent the synchronizer from sliding forward enough to let the rear shaft fit in the case. The solution was the same as before: remove the rear-bearing, assemble the transmission without the bearing, heat the bearing to expand it, and slide it on later.

I'm still not sure how it all is supposed to work, although we were always putting slightly newer gears into an older case. The last top-loader cases were model 78 from 1937. They might have a deeper recess allowing the cluster gear to drop further. The model 78 cases also have a larger bellhousing and fit over a larger clutch (11 inches instead of 10 and a half inches).

The next step was removing the old transmission from the truck.