When you have been repairing transmissions for several years, you can tell by looking at a gear set wether or not it has been abused. This junk yard C60 is one of those transmissions that likely saw many drag races and probably some street racing as well. The main giveaway is usually damaged synchro teeth, but thats never the full extent of the problem. This visual cue is what prompted me to contact my teammate John on what direction to go, so here is where Part 2 begins. A full teardown, close inspection, and repair.
Once you press off the input shaft rear bearing, spin it freely in your hand and pay attention to it's operation. Also make sure there is no excessive side to side play, 4th gear and it's synchro will slide off at this point. You can see in the image this synchro took some damage on its teeth, and there is a bur on the top from being forced into gear. There is some wear on the gear as well, but nothing that can't be filed away.
If you look closely at the 3-4 shift hub you can see wear marks in the groves, these grooves are where the collar slides when you shift gears and is the part responsible for the actual transfer of power to each gear. Any wear in this area is proof that another part is damaged due to poor shift habits, usually extremely hard shifting. The collar gets pressed against the synchro with excessive force causing a grind from not having sufficient time to "synchronize" the gear speed to the shaft speed. This caused damage to the synchro, and the gear/collar contact points creating burs in all of these areas. So as you can see that's all bad and 3rd gear took most of the damage, but it's fixable so lets move on.
The pinion shaft is easier, press off 4th gear and the rear bearing together, remove the spacer then press off third gear. Second gear will slide off and then you remove the keeper and press off 1st gear and the shift hub together. I've never found a bad 1st gear synchro or gear, but 2nd sometimes takes a hit. You can see in the picture above that 2nd gear has a 3-piece synchro, and it's rare for a synchro like this to wear out due it having double the contact surface. Im going to replace it anyway since I'm here already and there are some strange marks near the teeth. Take a look at the whole disassembly below.
I'm going to replace the damaged synchros, repair the engagement points, and put all of this back together. The first step is to take all of the components to the parts washer and give them a good scrub. Next I'll file down the damaged engagement points, clean them again, then soak everything in gear oil before reassembling the shafts with the new synchros.
Now we are ready to put all of these gears inside the C50 case and hope everything fits properly. Stay tuned for Part 3, final assembly!
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