1946 John Deere Model LA Tractor Gets New Transmission Bearings - Part 3 of 5

 New bearings have arrived!

One reason I jumped into this project so quickly was because I'd run across a guy by the name of David Dow on Youtube who went through this exact process for replacing transmission/differential bearings in his JD LA. David's videos were just the thing to get me familiarized with the entire process. For that I am most grateful. David also mentioned the booklet below, and says it was published by Jack Kreeger. I tried finding the booklet online by searching for the Jack Krieger name and title but was unable to do so (later I found out I'd misspelled Jack's last name, it is Kreeger). I did manage to run across a booklet on eBay that looked the same as the one David mentioned (under the title "Shop Service Manual"), so I picked up a copy. I don't think the booklet is copyrighted so it appears anyone can make copies, but don't quote me on that. I highly recommend getting a copy.

The end of the pinion gear is supposed to have a number etched into it in the range of -5 to +5. I can see what looks to be the number 45 on top but it is more likely a +5, and then something etched on the lower side but I couldn't make it out. If I had to guess, I'd guess it is a zero.

There is a process to check to see if the pinion gear is at the right height to mesh properly with the differential ring gear. This process uses a spacer cut to about 1-1/8" that is placed on top of the pinion gear, then a 2" diameter rod spans the differential bearing valleys. A feeler gauge is then used to measure the gap between the spacer and the 2" rod (I made do with a 1" diameter rod). The thickness of the spacer block, the feeler gauge measurement, and the addition or subtraction of the number on the end of the pinion gives the correct height of the pinion gear relative to the ring gear. The magic number is 1.172".

In my case, assuming my "zero" number on the pinion gear is correct, the measurement between the top of the pinion gear to the valley of the differential bearings should be 1.172". If the number on the pinion gear were, say, -24, I would have subtracted .024" from 1.172" to get 1.148" as the correct measurement.

I cut a spacer to 1.159" and then measured the gap between the spacer and the rod to be .016". So the math is: 1.159 + .016 = 1.175. I am .003" over the magic number of 1.172" but I figure that will be just fine, as this tractor will not need to earn its living by pulling plows or cultivators anymore. It will live a life of leisure.

During disassembly of the transmission, the pinion shaft had 1/8" of play front to rear due to the worn bearings. The shaft is supposed to have no backlash and be difficult to turn by hand. Also, the differential is supposed to have .008" of interference fit into the case, but it was also loose because of worn bearings. These new bearings brought everything back into spec.

The ring gear has 42 teeth and the pinion has 8 teeth. These numbers are marked on the ring gear.

Things are coming together nicely.