in the fwiw column..... i tow a travel trailer. dealer said 'no problem' only 1/2 ton sub was what went thru my head...
< 100 miles, i shelled (and i mean shelled! like a granade went off in the pumpkin), the ORIGIANAL 3:42 ring/pinion.
Cha-Ching $1000 for a COMPLETE 3d member, rebuilt....
we tow a bit over the next 18 months or so, then we're gettin ready for a fairly long run. I notice the start of a rear-seal leak on one of the rear brakes... i have no time before we're due to leave, so.... off to the shop it goes.
They call later that day, and say they can't get it apart! seems the axle on one side won't push in to release the C clip... they figure something is dreadfully wrong, and want my ok before FORCING things... hard to fine correct spline count axle they say..
Well, $400 later, and a fixed seal/new axle shaft.. it's running again, but those axles NEVER AGAIN pulled the trailer! (dry weight of 4275 per MFR... 7235 Gross rating) I never figured i was even close..
WRONG!
adding a 14FF 4:10 cured things for me, but i do keep an eye on trailer weight now-a-days....
just something to keep in mind....
(your mileage may vary, professional driver lost on a trail, presence of humor in this post does not indorse comedy central)