Out of curiousity is there ever a mold parting line on these gears? It barely was perceivable when looking at the gears through a magnifier. We assumed it was a crack. I know the ones on the BL2 were much more visable when I replaced them. Jim
I agree with you about a parting line. What I believe a contributing factor is that the hot plastic enters the mold and passes around the mandrel. Where the plastic meets on the far side of the mold there is a "chill line" which may or may not be exactly at the mold parting line. This, plus the critical interference fit that can't be too loose nor too tight to hold the axle from spinning in the gear.
I've seen the same thing happen with other injection molded parts especially when the plastic has to pass around a shaft opening, mandrel.
Look at this barbed ball, one still on the sprue and the other one on the shaft. Split wide open but not at the parting line:
IMG_5946_fix by Edmund, on Flickr
Cheers, Ed
When we looked at the gears the crack was so imperceivable we almost thought it was a parting line- still question a little. I did lube out the gears and it smoothed out. I think I will run it up at the club next week and see what happens. Noticed the noise more on the grade while under load. When I had one in the BL2 it was much louder with the thumping and the crack was very apparent.