2012 peterbilt 587 grinding in gears 7 through 10

I would take it back to Peterbilt. Is it a 10 speed?

 

I would think it would grind in 5-6 upshift or 6-5 downshift shift if something was wrong with the synchros. Either way, I would take it back to Peterbilt. What were the symptoms when you brought it to them?

 

The AC issue is not related to the trans issue, but it is possible the tech could have disturbed an existing wiring problem, or left some wiring disconnected, but it's hard to say. Its the same with the coolant leak, it's not going to be related to the trans issue, but if for some reason the tech disconnected any coolant lines, there could be a leak now. But that's pretty unlikely. I'm not too familiar with Pete's, but I can't see a reason they would need to disconnect any coolant lines to get to the back box of the trans.

 

I would take it back to Peterbilt.