Just for info:
This last weekend I took the first step in converting to a synthetic lube (Transynd) in the transmission. I just wanted you all to know the benchmarks I saw in refilling the tranny. It appears I have the 2 inch pan and I presume most Prevosts have the same. It matters pertaining to which filters one uses.
I dumped the fluid from the pan using the drain plug and I loosened the 12 bolts on the two filters so fluid would drain out of the those cavities. I did not drain the lines going to the trannny oil cooler. I got about 6.5 gallons out by letting the stuff drain for about 1.5 days.
I put in 5 gallons: There was no evidence of fluid on the dip stick.
Added a gallon for a total of 6 gal: Evidence of fluid on the bottom of the dip.
Added another gallon for a total of 7: Fluid was at the high cold mark.
Ran the coach for a bit until the oil temp was over 160: Fluid level was just shy of the low hot mark.
I added another half gallon. Will take the coach out next weekend and get it all the way up to operating temperature and check again.
Why didn't I change the filters? They were new last August.
My plan:
In about a year I will dump the fluid again, and change the filters. That should get rid of most of the old fluid. There after I will do the filters (a filter change will drop about 2 gallons) for a couple of years, then leave it alone.