Originally posted by Roger
Is it the drivetrain, bulkhead, or the front one-way ring gear that's causing the gear to strip due to impacts. I've seen numerous modifications on front one-ways fail. Have you ever thought that it's not the front one-way, but maybe the whole drive train system ?? True, its fast just like other shaft driven cars, but why is it just this car ? How come the TC3 or the yokomo SD don't have problems like the evo3 ?
The problem is with the way Tamiya made the center shaft system. All shaft drive cars need to have the shaft float so any slight misalignment between it and the gearboxes and any chassis flex won't make the whole drivetrain bind up. The difference between the Tamiya setup and the TC3/SD is that the others use a 3 piece shaft system. On the TC3/SD, the front and rear pinions are mounted on fixed stub shafts and the bearings are tight in the gearboxes. This allows for consistent, correct gear mesh between the ring and pinion gears. The center shaft being a big dogbone sitting in drive cups still floats.
Tamiya's setup is a single shaft and it floats by sliding in and out of the pinion gear (That's why racenut123's stripping the "D" out in the pinion) and the slop between the pinion bearings and the holes they sit in in the gearbox cases. The system floats by the slop.
If you wiggle the EVO 3 center shaft, you'll notice the front has more up/down, side/side play than the back because of the lack of the extra bearing that the rear (in the motormount) has. This makes the front gear mesh really inconsistent and poor. Add to the fact that the front uses a 1 way with no give (diff action) you'll strip gears. You can add a bearing in the front plastic support but I think Tamiya left it out so the drivetrain would be less likely to bind up ie. have more slop.
I don't know why Tamiya did this. Their nitro cars like the TGX is shaft driven yet has a 3 piece system just like the TC3/SD. Why did Tamiya go to a 1 piece drive shaft system on the EVO 3.
Now you, racenut123 and aurra sing know why I have not driven my EVO 3. I need to fix this first. I saw someone convert to a 3 piece system using SD parts or I was going to look into using the Tamiya nitro car's pieces but the Tech Racing 3 piece shaft kit looks good.