KW c500 double set back tandem tandem 8X8 help

[Lil Giants]

I got the Blackwell axles and took them apart... a solid axle with no differential. Not a good choice for your bed trk, you'll chew driveshafts & transfer cases.

The rcbrim axles look like a good fit for your needs & are servo lockable via a cable. RC4wd now has them stock again (atleast a few weeks ago they did). I got these axles in the same order.
http://store.rc4wd.com/Scale-Semi-Tr...ue_p_3791.html

Apparently there is stronger version yet, though I don't know from experience or the grapevine if it warrants the 2,5x the cost... but maybe getting one for the front diff of rear tandems b/c that will be the most abused axle for putting power to the ground.
http://store.rc4wd.com/Armageddon-8x...ff_p_3839.html