Glad to hear the electrical problem is fixed. If the idle is too higfh, the clutch will still be engaging the belt, making it hard to stop. Therefore the brakes may growl. BUT! even if everything is correct.. idle, brake adjustment ect... the brakes may still growl and chatter and carry on. On the 6x4 and some others, the brakes are inside the transmission. They are of the wet type and actuate with what is known as a ramp and ball system. There are a couple solutions to reduce or eliminate the growl, chatter, grind.
First off.. Change the oil in the transmission. Refill with fresh LOW VIS Hy-Gard. No NAPA or TSC or WALLY MART CRAP.. actual just bought JD Hy-GARD. Now go out and run the heck out of it. Use the brakes.. ALOT! Use pedal and gas at same time.. ride the brakes. Warm them up.. Your problem will soon go away.
Still growling? Change fluid again.. this time add some PEMO. PEMO is a friction mod. Available at your Deere dealer. Its a lil pricey tho. Still may take some time to "kick in" and get rid of the growl, chatter, squeal.
Use common sense and dont use or ride the brakes til you burn em up or overheat transmission. Figured I'd throw that in there just in case!