If you want, you can disconnect the connector for the RDU clutch/module which will make it run in full FWD mode. This could help you feel the difference with no load to the rear.
I have no experience with any, but I did notice that the case of the inner CV for the TrakMotive is circular, while the GSP looks like the OEM one.
Another thing I noticed, the rear OEM Axle part number was superceded once only, unlike the fronts which changed 5 times, at least.