Second gear noise - 40c and 420c final drive housing?

[hydrogeo]

I have a subtle knocking sound coming from the trans in second gear only on my 40c. Seems worse when the motor is lugged, but it's not horrible. All the other gears, including reverse, are quiet. Seems to shift fine.

I have both a parts and service manual, and I can't quite sort out how second gear is situated on the input/intermediate/output shaft from the pictures, and whether there is a bearing particular to second gear.

Anybody that's had one of these transmission apart have any thoughts on what I should look for before i pull the shifter and look around? I really want to tear everything down from the engine clutch back and check all the bearings, but time resource is my issue.

Also, I have what appears to be a 420c final drive housing on the left side (has the gussets). A friend has a spare right side case from a 420c. I just want to confirm it will fit and that what I am looking at on my machine is not instead a later 40c-specific case. I really would like the stronger case on both sides.

Thanks!

[Lavoy]

Most likely a chipped tooth, no way to daignose without pulling the top cover. No way to fix other than total tear down, sorry.
The gussted case is the later 420 final and is a direct replacement for the 40 final.
Lavoy

[hydrogeo]

Thanks, Lavoy. I'll try and pull the cover this weekend. If the gear is bad any chance you have one? I guess that would give me the motivation I need to tear it all down.

[Lavoy]

It's possible, would need to dig a little.
Lavoy

[hydrogeo]

Pulled the shifter, and nothing obvious. Reviewed the service manual and it does show the gear layout (was looking in the wrong place). No obvious chips, and there is no excessive wear anyplace. I'm going to give it one more good once over and button it back, up unless anybody has any other input on something to check?

Also picked up the later final. Got the whole thing including the clutch assembly. Lavoy, when I swap the later final in do I need swap out all the internals, or are the 420 bull gear and pinion the same gear ratio as the 40? Don't want to drive in circles.

[Lavoy]

I would never install a used take off final that I know no history on. For all you know, it is only a few hours away from dropping a bearing and destroying itself. Pull the final apart and verifiy that the gear set is the correct tooth count, and that everything is in good shape.
Lavoy

[hydrogeo]

The parts machine was in pretty good shape, but the main reason it turned into a parts machine was that the other final blew apart.

I am going to take your advice and try to find some time to tear everything down from the trans back later this fall.

[hydrogeo]

Well, put it back together and no more noise, quiet as can be in all gears. Ran it for 5 hours this weekend and still good. The only thing I can think of is that I made a new gasket for the cover with some thicker gasket material. It may be that the thinner gasket allowed the shifter fork to hit somewhere. Anyway, all is good. Still planning on tearing into the finals this winter just to check things out.