Removing the broken old gearbox
This is the part I’ve been avoiding and procrastinating on the most. Originally, this car “died” because of the gearbox giving up. I had never done an automotive repair of this magnetude before, so I was quite intimidated going into it. When I started the restoration there were no used gearboxes for sale, so I started by doing other things first and leaving the gearbox as is.
In October of 2024 I found someone who was selling their Rocky and was selling a spare gearbox along with it. I bought the spare gearbox off him, not knowing the condition inside. I pulled out my original gearbox, which was a massive pain as I don’t have the right tools for the job. After a lot of cursing, blood and sweat, the broken gearbox was out.
I then noticed the gearbox I had bought had a vacuum controlled transfer box for the 4WD system, while mine had manual levers. This means I had to split apart both the old and new gearbox so I could put the manual transfer case on the new gearbox.
The idea was that I would just throw this combo in, fill it up with oil and drive off. Unfortunately there were some more obstacles in the way.
Clutch and flywheel
Before this gearbox could be installed there were other issues that needed to be addressed. The flyweel was covered in hot spots from aggressive driving, and the clutch was so far gone the rivets had started shaving off.
I had the old flywheel resurfaced by a local machinist and put in an upgraded clutch by LOF Clutches .
Another pushback
Now it was time to bolt in the new gearbox and hope it all worked out. I bolted in the gearbox, filled it up with oil and turned the key.
Straight after firing up the car, the gearbox started making violent metal noises, meaning the mystery gearbox I purchased was no good. I opened it up and sure enough, there were sparkly chunks of metal in the oil…
Feeling defeated after this massive disappointment I took a break from the project, and when I got back into it I procrastinated on the gearbox by doing other things first. While working on the brakes and suspension I kept passively looking out for used gearboxes. I then stumbled upon a Daihatsu specialist who still had a bunch of new old stock parts from the 90’s. I inquired about a gearbox and luckily he had one in stock.
Third time’s the charm?
When I arrived to pick up this third gearbox the mechanic told me he’d replaced the third gear synchro the night prior. I paid the man and took the gearbox home, where it sat for a few months. When I finally got the courage and time to tackle the gearbox install again, I started by verifying if the box would shift into all gears. To my surprise, the box would shift into 3-4-5-R just fine, but 1-2 seemed locked out. When I reached out to the seller about it, he just told me to check if all the shifter forks were aligned correctly.
I took off the lid and looked inside. The shifter forks all seemed to be properly engaged, yet no matter what I tried, 1-2 would be locked out. Investigating the issue further, I found the actual 1-2 selector gear was mounted the wrong way around. The seller must’ve rushed the installation of the synchro and put it back together incorrectly.
Time to go down the rabbit hole
So that leaves us with 3 broken gearboxes, 2 of which are probably scrap and one that should be saveable, although it would require rebuilding it again. To get an idea of the complexity of a gearbox, I’ve included an exploded view diagram of it below.
With nothing but this low resolution scan to go off, I figured it would be a good idea to practice the gearbox rebuild on the broken boxes. I figured I might be able to make one working gearbox out of the parts of the other two. I started tearing everything apart, being careful to note how it all went back together.
I took the best pieces of both broken gearboxes and put them together to form a complete gearbox. While I’m certain I did everything correctly, the bearings bind up more than I’d like, suggesting the input shaft I’m using might be bent. Unfortunately I don’t currently have access to the tools needed to verify this suspicion.
Feeling I now had a decent understanding of what to do I tore apart the third gearbox, flipped the 1-2 selector gear around and put it all back together.
I reassembled it, torqued everything back up to spec and tried rotating the input shaft. After verifying it rotated freely and all gears engaged properly, the shifter forks were reinstalled. Now for the moment of truth, the shift lever was installed and all gears engaged without any issues. I attached the bell housing, and now the transmission is ready to get bolted to the transfer box and to be mated to the engine.
