Sorry guys, you won't be able to upgrade TBe3 to TBe4.
About 95% of the parts will be different!!
Only thing recognisable on the TBe4 manual are the J-parts (battery holder) and the spurgears.
Chassis plate is new, mounting points for new gearbox is different so these parts cannot be retrofitted to TBe3.
Can new bevel gears fit? Will have to wait till they ship... but seem to be *both* sold with bevel pinions in the bag.
51109 TBe4 ONE WAY GEAR SET gives 2x Oneway Ring Gear, 2x Bevel Pinion gear
51110 TBe4 BALL DIFF GEAR SET gives 2x ball diff Ring Gear, 2x Bevel Pinion gear
TBe4 suspension hingepins now sold separately... 51093 (46mm), 51097 (10mm screw pin), 51098 (22mm screwpin) & 51099 (25mm screwpin).