My experience with terex: endless trans and brake issues, had no issues getting new parts but they are very expensive! Had a power divider get chewed up on a TA30, needed the pinion shaft, bearings etc. Quote was over $30k for parts!!!! Couldn't find a used diff so they parted it out. I had some good conversations with the mechanics at a large contractor in Williams Lake BC, they had a large fleet of terex artic trucks, after years of trouble and headache they sold them all and bought Cat.
I don't have much experience with Volvo artic trucks, but I can say they are much more dependable then Terex.. I believe newer Terex are made by Volvo?