Cracked Gears are a Common Problem on Many Machine from the 60s' and on!
Cracked gears can ruin an otherwise good day of sewing. Most folks can't fix these and it is the number one reason otherwise great machine are given to thrift stores, sold on Craigslist, or thrown away. Many folks that have a good deal of mechanical aptitude can and do attempt to replace the gears in some of the more straight forward machines, inevitably I get the machine to finish it off. When you change most gears it is likely to throw off the timing of the needle to hook and the needle to feed dog. Even for folks with high levels of mechanical reasoning these two procedures are nearly impossible.
This picture of a cracked gear came from a otherwise gorgeous Kenmore 158.xxxxx. It is the gear that drives the zigzag and decorative stitch motion. The part sells for $20 and it cost $35 in labor to install...FAR FAR LESS THAN A NEW PLASTIC MACHINE! Plus the new gears are made of better material and the gears themselves are designed on computers (CAD) and cut on computer driven machinery (CNC).
Many owners of Singer sewing machines notice that when new gears are installed that the machine runs both smoother and quieter.
We made it run like new again!