I'm not sure about Goldwing trikes, but I have seen some DIY trikes where the axle had to be fitted wrong way up.
DriverRider is correct, i have seen a few diy trikes that flip it over to match the rotation but i dont think a kit form any dealer would be set up like that. and if there is I would not spend a penny to by it.
Those were bikes that had the drive shaft on the left
side of the bike originally, not the case with a GoldWing of any year. All shaft drive bikes have the ring gear between the rear wheel and the pinion. To make a "trike" go forwards, the ring gear must remain on that same side of the pinion as it was withthe original "bike".
They'll work just fineup side down if the vent hole is welded / plugged shut and a new vent added on the new top side and if the pinion bearings themselvesget ample lube.
The rear ends in cars are greatly " understressed" inaMC based Trike use. Most old old old old car rears were simple bevel gear setups where the pinion was on the same center as the axle and in those cases, there was no problem with flipping the rear other than it reversed direction.
In fact, Smokey Unick used to flip the rear axle of some of his Hudson Hornets in the veryearly '50s ... the early days of Nascar ... and he had a "reverse grind" camshaft ground for the engine which allowed the 308 CU IN Hudson Twin H POwer 6 to run backwards. His reasoning was that the torque reaction coming off the turn was better used by the chassis on the dirst tracks of the time. It was a short lived experiment, it likely hurt actually, but he tried it just the same. He was an innovator. Once at a post race inspection due to a competitor's cry of foul, NASCAR actually wanted the camshaft out of the engine for inspection. Smokey and crew removed it under the watchful eye of NASCAR, but as he handed the shaft to the inspector, it dropped ... hard... and being cast iron, it broke into many pieces. They were able to check lift and duration, it was ruled OK, and no fiurther inspection was done.
Now .... the rears have hypoid gears and the pinion is below the axle and lube levels assure ample lube to the pinion bearings. If flipped, the pinion is higher .... which is OK IF it get's ample lube. Some rears have webs that take gear oil slung from the ring gear and feed it to pinion bearings like my '77 F150s front Dana 44 High Pinion axle which is basically a regular Dana 44 simply rolled backwards .... not flipped .... so the pinion points towards the transfer case but rotation direction remains correct.