Small Engines (Lawn Mowers, etc.): Craftsman self-propelled transmission problem, worn gears, self propelled lawn mower

Question
Out Craftsman self-propelled lawn mower isn't working correctly, in that the front wheel drive isn't engaging (Eager-1, 6.5 hp, 22", Model #917 376310).  The belt spins, but when we try to engage the drive it won't click into place and go anymore.  It does do sort of a shuddering when we try.  I don't know if we need to replace the transmission (which I could probably figure out, although the part appears expensive), or if there's something I'm missing that would be easier to fix.  There is some sort of little round plastic thing on the transmission; is it for lubricating the transmission, or is that not the likely problem)?  Thanks!

Answer
Hi Paul,

If the lever on the transmission is fully moving and the problem isn't just in the cable or linkage, then the transmission is probably defective.  You would need to disassemble it and look for any problem, including worn gears.  Check the wheels for worn gears also.

Let me know how you make out.
Michael