How many would be interested in this service?
 
$150 seem fair to R&R and lube the plastic gear with a new one with a lifetime warranty?  
 
Some of you suggested I just pick one up at the junkyard.  They wanted $50 for the whole thing, but I would not take it until I took it apart and looked at the gear.  They let me.  I found the gear was brittle, cracking and on the way to failure, so I passed even though it was operating.
 
If you want to DIY it, you can find the gear at odometergears dot com  
 
my gmail: appliedracingtech ...if you want my help 
