[Adam Skelding]

My checklist would be:

1: Bearings.

2: Then check the end float of the G/Box input D/S on the input gear. If it's running tight then you might be causing excessive friction by putting too much preload on the bearings. Normally I put the input gear between the bearings and mount it in the gearbox half. Then slide on the collar until there is almost no play and tighten the grub screw. Spin up the shaft and it should feel nice and free with no end float.

3: Check the barrel and CVD pins in the Djoint. I replace mine about once every couple of months (useage dependant). I use the Tamiya anti wear grease to extend the life of my CVD's, it's a bit thick but really lowers the wear. Once the pin wears then the barrel and cvd joint get an increased amount of battering due to the slop induces by the wear.

My guess is that #2 will be the main issue a little too tight can mean a hot gearbox.