This Dakota has always had a loud gearbox, but lately it seemed to me to be louder than usual. I'd recently removed the carpet from the truck, which frankly was enough to cause the increase. However I was unsure if maybe the noise level was abnormally high due to bearing wear and I was only now aware of it because of the bare floorboards. I've never rebuilt a manual gearbox before; seems like a learning opportunity. It should be noted at this point, that I've always had trouble with downshifts into 2 and 1 on this truck, particularly in cold weather. This will come up later.
Like anyone who is jumping to conclusions without doing any proper diagnostics, I order a rebuild kit first. However, due to reasons involving price tags and sleep deprivation, I only order a bearing kit. Not in fact one that contains new blocking rings (synchros).
Here are a few pictures from the tear-down:
After disassembly and inspection, I conclude that the bearings look outstanding for their age. The blocking rings however are quite worn. In particular the reverse ring (which is plastic) is over 90% worn through. Reverse is not synchronized on this transmission, but neither is it a sliding-idler design. It's continuously meshed like the forward gears. First, second, and third have non-trivial wear on both the conical meshing surface and the tell-tale wear on the dog's teeth of poor engagement.
I also learn from some documentation I found that the wrong lubricant was in the gearbox. When my dad had bought the truck in 2003 it had gear oil (80 weight or so). As it happens, this transmission is designed to run on 10w30 synthetic engine oil. This was the cause of the poor downshifts. The heavier oil was much harder to scrape off the conical section of the gear (where the blocking ring pushes on it during a shift) and match speeds, resulting in forceful shifts being required. Of the various blocking rings, I discovered fifth and second were identical (though had differing amounts of wear). So I swapped them. The others I left where they were.
During the process of changing the bearings, I needed a hydraulic press. So I built one. Neal had been lamenting the lack of one and graciously supplied the steel and bottle jack. I grabbed some old grade-8 bolts and got to welding.
I changed all the bearings, unfortunately the snap rings included with the kit were either mismatches or of obviously inferior quality so I only ended up using one or two of them. I decided the synchros were good enough for a cheap truck and re-assembled the transmission. The end play on the layshaft didn't change and everything moved smoothly.
Overall the rebuild was a success. It sounds the same, but it shifts much more nicely. Second gear is much more pleasant, fifth a little less so. I would have like to have new synchros, but it's nice to learn just how much the difference in wear between 2 and 5 can affect shift performance. Downshifts have been improved across the range thanks to the change in lubricant.
This big snap ring was a major pain in the mctukhus:
My channel locks were just a hair too wide for the clearance. Much patience was required.
All the pictures I took as re-assembly notes can be found in the gallery.