Inside the coach, I found a u joint under the hard plastic boot that covers the steering column in front of the drivers chair. On our 1991 Contessa there were 2 joints in this area.
Outside the coach, in the chassis area on the Marquis there is another u joint about 6 inches below the floor and just above that u joint is a collar that also has a zerk. I take it that is for a sliding shaft.
These two zerks are just above the steering box. The steering box also has a zerk on the back side of the box covered with a plastic cap that fits right over the zerk itself.
To grease the u joint zerk above the steering box I had to turn the steering wheel far to the right to get grease gun tip onto.