I've just finished building the chassis of my new scx10ii. It's been a fun build. The quality and attention to detail is a step ahead of my wraith. The below findings and fixes worked for my paricular truck. There may be variations with others.
The first apparent issue i can to was the diff bevel gears. Once assembled, they were graunchy and gravelly in one direction, as many other people have found. I immediately read up on this forum. Unusually some of the recommendations were off the mark for my truck. What i found was that the shaft needs assembling to the diff to correctly complete the workings. The shaft coupler acts as a backstop, correctly locating the pinion on the crown gear = no more graunchiness. There was absolutely no need to try to shim anything, and 'running in' with a drill could have damaged the gears.
The next head scratcher came with the transmission. On first assembly, (step 19 in the book) something was obviously wrong. Very notchy. A bit of reading again, and this time, partial success. The gears are sided, although not meant to be. Flipping the bottom gear improved things. The gears now were mostly smooth. If i pulled each shaft outwards, it ran smooth. If i pushed the shafts inwards, notchyness.
I pulled it all appart again and looked at how the gears meshed. I noticed the big gear was running right up close to the collar on the end of the small gear, and could even see signs of contact on the edges of the big gear.
I took the big gear to the bench grinder and ground a small chamfer onto the edge:
I reassembled, and the 'box was now acceptably smooth. Hurrah..... but whats all this top shaft slop?
I had about 1.5mm axial (!) slop of the top shaft. I measured everything up:
The stack of parts had about 0.2mm clearance inside the cases - pretty reasonable.
The slop was the shaft moving inside the stack. As identified previously on the forum, the pin slot in the top gear appears too deep, so the shaft pin is not restrained between the bearing and the gear:
I can't help but think that the arrangement will make more sence once all the two speed parts are in there too. Either way, i think this slop is more of an aesthetic issue rather than a problem.
Looking at the end bearing with the shaft pulled back against the first bearing, the slop gap can be seen as the shaft end vs the bearing face (out of focus - sorry):
To eliminate the slop, i cut a 1.2mm thick spacer (to match the gap) from a piece of 4mm diameter sprue, and poped that in the end:
This acts as a thrust face at the end of the shaft, taking up the axial slop but leaving a comfortable 0.2mm axial clearance.
Job done. For free. Very easily.
Next i assembled the transfer box (step 20). Arrgghh. Graunchy notchy hell again.
This was again due to the gears being sided. I think there must be a very small amount of draft on the gears from the sintering process.
I made sure the first two gears were reversed to each other (unlike how shown in the book) and then tried the bottom gear both ways to find the smoothest fit.
With blisters on my fingers from all the screwing and unscrewing, i finally had a complete, smooth transmission. 8)
The first apparent issue i can to was the diff bevel gears. Once assembled, they were graunchy and gravelly in one direction, as many other people have found. I immediately read up on this forum. Unusually some of the recommendations were off the mark for my truck. What i found was that the shaft needs assembling to the diff to correctly complete the workings. The shaft coupler acts as a backstop, correctly locating the pinion on the crown gear = no more graunchiness. There was absolutely no need to try to shim anything, and 'running in' with a drill could have damaged the gears.
The next head scratcher came with the transmission. On first assembly, (step 19 in the book) something was obviously wrong. Very notchy. A bit of reading again, and this time, partial success. The gears are sided, although not meant to be. Flipping the bottom gear improved things. The gears now were mostly smooth. If i pulled each shaft outwards, it ran smooth. If i pushed the shafts inwards, notchyness.
I pulled it all appart again and looked at how the gears meshed. I noticed the big gear was running right up close to the collar on the end of the small gear, and could even see signs of contact on the edges of the big gear.
I took the big gear to the bench grinder and ground a small chamfer onto the edge:
I reassembled, and the 'box was now acceptably smooth. Hurrah..... but whats all this top shaft slop?
I had about 1.5mm axial (!) slop of the top shaft. I measured everything up:
The stack of parts had about 0.2mm clearance inside the cases - pretty reasonable.
The slop was the shaft moving inside the stack. As identified previously on the forum, the pin slot in the top gear appears too deep, so the shaft pin is not restrained between the bearing and the gear:
I can't help but think that the arrangement will make more sence once all the two speed parts are in there too. Either way, i think this slop is more of an aesthetic issue rather than a problem.
Looking at the end bearing with the shaft pulled back against the first bearing, the slop gap can be seen as the shaft end vs the bearing face (out of focus - sorry):
To eliminate the slop, i cut a 1.2mm thick spacer (to match the gap) from a piece of 4mm diameter sprue, and poped that in the end:
This acts as a thrust face at the end of the shaft, taking up the axial slop but leaving a comfortable 0.2mm axial clearance.
Job done. For free. Very easily.
Next i assembled the transfer box (step 20). Arrgghh. Graunchy notchy hell again.
This was again due to the gears being sided. I think there must be a very small amount of draft on the gears from the sintering process.
I made sure the first two gears were reversed to each other (unlike how shown in the book) and then tried the bottom gear both ways to find the smoothest fit.
With blisters on my fingers from all the screwing and unscrewing, i finally had a complete, smooth transmission. 8)
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