Hello,
How heavy is your RV loaded when this occurs? Are you out west at higher alt? Tire pressure up? Pulling something, Air Conditioner on , boat on roof? High winds?
In my mind from driving( my 22R standard transmission) on hills, I could guess that any more of a load (any or all of extra engine loads above) could cause the transmission to start looking for rpms somewhere besides the engine. (It will Shift down) In Overdrive? Wow....mine standard transmission only has 3 gears forward and I can't imagine what would happen on a hill with less RPMs than I have in 3rd now. wow. FYI at 60 mph on a flat with a light load I get real close to 20 mpg)
Without being an 'expert' I'd say you're maxed out in power, and I think that when the rpm jumps up like that, the clutch in the automatic transmission is slipping because of so much toqure and so few RPMS. NOT GOOD. Don't let it do that. I'd manually put the auto transmission into 3rd and let the speed be what it may.
When driving an 'underpowered' car (64 VW) I have always pushed my speed up as high as safely going down the hill to help me climb up the next one. RPMs are everything on a hill, and when at higher rpms, there is much less toque on your clutch. It works for me driving from Utah to California but that means 70+ going down, and 55 or less going up.
A lot of this may come from driving on interstate and trying to keep up the 70+ mph. Take that back roads, much nicer, and you can drive at 55 and not feel pushed.
Richard
