Having read through the forums to solve my issue with a gear slipping, I feel I should share my story to help others who may have this problem.
I recently re-mounted my dual extruder on my Taz 6. When I went to print PLA, the print would work fine for about 5 to 10 minutes. Then the extruder gear would start slipping and the filament would no longer feed into the extruder. I read through the forums and it appeared that I had an issue with heat buildup on the PLA as described elsewhere.
Two things fixed my problem:
First, I checked the fan with the M106 S255 command in the control box for Cura. Once I confirmed the fan indeed worked I went through my Cura settings and found that I had turned off cooling previously. I set the fan min speed and max speed both at 100%. That seemed to work for me. I believe that Lulzbot printers only function at 100% or 0%. If I am incorrect, please let me know.
Secondly, I noticed that the fan did not seem to be blowing on the extruder. I had read elsewhere that individuals had replaced the stock fan with more powerful 3rd party fan. Being a noob, that intimidated me, but I decided to remove the fan cover and take a look to determine how difficult this would be. When I removed the fan cover I discovered that a bolt had somehow gotten in the fan cover and it was obstructing the air flow.
These two things have allowed me to print PLA without any problem. For anyone who experiences gear slippage after the print starts out working just fine I would advise you to start looking at the heat creep(buildup) threads on this forum.