Official Erevo 1/8 scale center diff thread

[simplechamp]

Here are the output shafts with gears mounted in their current state. The pinholes are exactly 0.229" (5.8mm) from center to the end of the shaft, so please note that isn't the correct measurement to use. I did make the shafts a tiny bit longer just in case something like this happened. If they were going to be off I wanted them to be long. My main concern is that the part of the driveshaft that mounts to the outputs will be too close to the trans case and hit it or rub.

Currently the shafts are 29mm and 41mm. Each shaft wil have to be ground down another 2.5mm to be flush with the gear. This will leave the final lengths at 26.5mm and 38.5mm.

Compared to the original measurement suggestions (27.2mm and 40.6mm) the smaller shaft will be 0.7mm short and the larger shaft will be 2.1mm short. So the total length I've lost is less than 3mm. As you can see by the difference in the 2.1mm and 0.7mm I wasn't very accurate in my original cuts, but hopefully that will work to my advantage since they are longer than suggested. Hopefully this won't be as big of an issue as I first suspected. The 0.7mm isn't much, but the 2.1mm lost from the longer shaft is what I'll be most concerned about.

Now drilling/tapping the hardened steel, that will be a much more difficult issue. I still think there is something weird about the machine shop saying they couldn't do it. It's not a shop in someones garage, it's a huge shop with thousands of dollars of CNC mills, lathes, and other heavy duty machinery. And they want to tell me they can't do a job multiple people here have done in their basement workshops? Just doesn't add up...

Anyway, I'm going to keep on trucking. I've put a lot of time (and a modest amount of money) into this and not going to give up now. Sorry to clog up the official thread with a bunch of my ramblings. Maybe it will help someone avoid the same mistake in the future. I'll post the exact measurement from pinhole center to the end of output shaft once I grind them down and make them flush against the gears.

Thanks for all the help you guys. Wouldn't have been able to do this without everyone else helping. I know it will be awesome once everything is finished!

[mistercrash]

I went in the garage and dug up the original output drives of my Ofna diffs and you are correct in saying that 0.229'' is wrong. I gave you that info and I'm sorry. I measured 0.190'' and that is from the original output drives of the diffs, not some bogus calculations from CAD drawings like I gave before. When putting the original output drives in the gear, they do stick out a little bit but definitely not as much as your pic shows. The part that sticks out on the OFNA drive I measured as 0.018''. As for the total length of both of your output shafts you'll be left with after you shorten them, you will have to try them to see if the drive shafts fit without rubbing on the tranny case like you said. That machine shop with the tens of thousands of dollars, if not hundreds of thousands of dollars in equipment should invest in a 20 dollar carbide drill bit and an 80 dollar carbide M3 tap. Unbelievable that they said they can't do it. I suspect they just don't want to do it and they should be honest and just say so and explain why.