PM Is critical. I used the same gearboxes in my Panther for 4 1/2 years at Danville and NEAD events before one started to fail. PM Is crucial. Seal off the TU's from the outside (output shafts to sprockets and all holes) and then cover them to keep lubes in and debris out. See my Before & After page for pix http://www.rctankcommand.com/before-...er-photos.html for more. Note..... I said LUBES. Yes, two lubricants. Most guys lube the gear faces and ignore the TU shafts and bearings/bushings. The face of the gears run cooler and tend to throw off oil that the shafts & bearings need. Oil the TUS (I use Prolong or singer sewing machine oil) with a needle point tip. Don't drive the TUs by motor just work it in by hand spinning. Then lube the gear faces with grease and again work it in by hand turning. I use white lithium which discolors with wear telling me when it is time to clean or re-lube. Dark greases don't. Cover them to keep the grease in and dirt. wires and loose parts/screws out. It is them most stressed part in your tank. Take care of them and they will take care of you..