My third classic Mini started off to be my first full-size restoration project. Well, it’s definitely not a kind of the usual restoration as the body is almost in perfect condition. In contrast, the power unit is at the heart of this rebuild, with the second gear that won’t go in as the first major issue to be taken care of.
What I knew was that I had to take care about the gearbox. What I didn’t knew was the reason of the second-gear issue. The first thing that came to my mind was the baulk ring. Unfortunately, moving the car forth and back without running the engine won’t let the second gear go in either. The baulk ring went off the list.
A phone call with a Mini specialist brought up another idea: The bushing of the reverse gear might slip out of position and finally prevents the second gear to engage. Naturally, this is something you couldn’t analyze with the gearbox in place. Hardly I had removed the gearbox, I found myself to shift through all the gears without any trouble. Needless to say, I couldn’t identify a dislocated reverse gear bushing either.
The reason for my second-gear issue was finally just the splint that was used to connect the gear change rod to the gearbox. It was simply too big. The attempt to engage the second gear would jam the linkage half way down. Curiously, I was wondering about this before, but it required the gearbox to be on the workbench to teach me the narrow ridge of a proper working gear shift linkage.
Check the internals
Now that the gearbox was on the table, it would have been foolish to not take look at its internals. What I found was a mess. The dog teeth of the first, second, and third gear were all past the peak. The second gear was actually the worst with its teeth totally rounded off, but the others weren’t much better with a bunch of chips all around. Naturally, I couldn’t satisfactorily analyze its counterparts, the synchronizer hubs, without disassembly. But there was plenty of reason to fear the worst. Indeed I found the 1st and 2nd gear hub to be deadly worn, but fortunately the other one was left in good condition.
With the condition of the dog teeth in mind, it could be safely assumed that the baulk rings and some other internals were hackeneyed, too. Crunchy shifting seemed to be ignored by the pre-owner at any sacrifice. The list was finalized with the selector forks worn and a full set of differential internals. The tooth surface of the planet gears showed a step at the end of the contact area, and it’s safe to say that differential pin had lost its original shape.
Make or buy?
Though it seemed to be unnecessary to remove the gearbox at the first glance, the urge for a complete rebuild rendered itself quickly. With all major replacement parts listed: three gears, one synchro-hub, both selector forks, all differential internals, all baulk rings, and all bearings, the question arose whether it would be more economical to invest in a reconditioned gearbox instead of a rebuild – at least that was what my part dealer suggested.
However, my intention from the very beginning was to go the extra mile. What I did in the past on cars was basically to swap all kinds of parts, but now I wanted to learn about the matters of real engine rebuilds. I took the chance and went for the rebuild.
I started by completely stripping down the gearbox . Surprisingly, most steps were quite straightforward. Occasionally, it required some creativity to build a special tool, but the most difficult thing was to rate the wear of the components. Obviously, all parts were worn to some extent, but it took some time to separate the men from the boys. Fortunately, I could ask some old hands, and had an excellent text on the rebuild of manual transmissions at hand.
Browse the photos to get an impression of the rebuild and feel free to comment. Stay tuned!