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View Full Version : Help with gear mesh.


thestug
2011.04.06, 01:43 PM
I recently bought a 3racing CF diff cover set and a new 94mm body. I typically drift and have had no problems. As soon as I put a normal rubber tire back on the gears would click/grind under power. The diff gear was slipping against the middle gear. I run atomic plastic ball diffs in the front and rear. I was kind of looking for a new set of gears. I was wondering if anyone has used a 3racing CF diff covers and atomic diffs and had good gear mesh. I was thinking of buying atomic metal pinions,delrin middle gear, and diff gear. Would this combination work well as far as mesh is concerned? Also, I have heard of shimming a diff. I assume this works by placing the shims between the bearing and the diff to shift it left or right as needed, right? This might not work because I'm not sure the CF diff cover has extra room for shims. Any help will be much appreciated.

thestug
2011.04.07, 09:39 AM
bump, anyone?

EMU
2011.04.07, 10:06 AM
It definitely sounds like you need to shim the diff. If I remember correctly there is enough room to shim in the 3Racing setup. What I try to do is first put as many shims as I can install on one side of the diff (push the diff spur away from the driveshaft pinion), just to see how many sheems you will need to work with. You dont want to bind up the rotation of the diff. After you know how much shimming you can get away with, install the shims on the side to push the spur into the pinion, and install the remaining ones on the other side. It takes some time to get right, but you dont want to have a tight mesh or loose mesh. I dont like the diff to have much play, less than a millemeter movement side to side, if there is no freedom of movement, you may be binding the drivetrain. Too much, and your gear mesh will be inconsistent. The sweet spot is when the mesh is just a little loose, but you dont have any clicks or slippage. This will allow the car to roll a little more off throttle, and get better runtime/more speed.

thestug
2011.04.07, 03:41 PM
It definitely sounds like you need to shim the diff. If I remember correctly there is enough room to shim in the 3Racing setup. What I try to do is first put as many shims as I can install on one side of the diff (push the diff spur away from the driveshaft pinion), just to see how many sheems you will need to work with. You dont want to bind up the rotation of the diff. After you know how much shimming you can get away with, install the shims on the side to push the spur into the pinion, and install the remaining ones on the other side. It takes some time to get right, but you dont want to have a tight mesh or loose mesh. I dont like the diff to have much play, less than a millemeter movement side to side, if there is no freedom of movement, you may be binding the drivetrain. Too much, and your gear mesh will be inconsistent. The sweet spot is when the mesh is just a little loose, but you dont have any clicks or slippage. This will allow the car to roll a little more off throttle, and get better runtime/more speed.

I shimmed the diff last night and got the gears to mesh right ,but I think I need to re-do the shimming. I put 3 shims on one side and now It whines a bit,but it is better than clicking. I will try what you said later tonight and shim it to mesh right and shim for minimal diff "play". There is quite a bit of room for shims in the 3racing CF setup, but not excessive. So I may end up using 1or 2, .1mm shims on one side and the rest(4-5) on the other side to get it perfect. Thank you for you very helpful post.