I don't recall what the reduction is for portals but I want to say it might be as much as half of the gearbox output. Every time I've had any issue with my big beefy axles on my green C24, it's been the ring gear grub screw. No matter how much threadlock, every year they seem to need maintenance.
It was Weird, the back on, just on one side was not moving. Noticed the housing screw on top is stripped or no threads. Enough pressure and the housing opened allowing the large gear with pin to separate and slip. I THINK. LOL i got it back together but i am getting binding on the diff. Any pressure on it... It binds... They are getting set aside for now. I am enjoying my Truck way too much to change anything now. I think it is 1:4 on these portals. I Love your c24 :) Stupid metal drive shafts bind at to much of an angle so my truck is a little lowered now. Doesn't look bad. I am taking it out today. THANK YOU MY FRIEND> :)