Reverse idler gear teeth number

[ronecc]

I have my gearbox stripped down and am in the process of fitting new parts. I seem to have come across something odd. In what I have read, the Reverse Idler Gear has either 18 or 21 teeth. I have one well worn one to replace. Trouble is, it has 17 teeth??? I have counted numerous times, and also let my wife count them, we both get to 17. Can anyone throw any light on this? The gearbox is an old Silver Seal and I am wondering whether the builder just threw in what he had laying around.

[JubileeNut]

Its not just the number of teeth you need to worry about but the tooth thickness alters and put one in that does not mesh with the other 2 gears and nothing will move!
I have the chunky teeth in mine and sometimes it hits tooth to tooth and you have to dip the clutch to spin up the box and then it will go in perfect. About 1 in 3 times this will happen. I suspect the fine tooth version is better and does not have this problem. I though it was 18 or 21 teeth.

[ronecc]

I need to replace both the idler and the 1st/2nd gear hub, so if I ask the dealer to check that they mesh, I should be okay then?

[JubileeNut]

first motion shaft also meshes with the gear hub I think so check all mesh together