I had missed the part about servicing the 90 degree box and first decided to change the oil in it at 40,000 miles. Did it again at 60,000. I had read about the box failures, so at 82,000 miles I had a new Curtis one installed intending to have the original for a spare, just like the spare DEF head I have carried. Then out of the blue, we decoded we didn't need the coach in our current lifestyle. It sold to the first party to look at it. At least now, he has a new gearbox.