I was coming back on the highway the other day with the cruise control on my 2008 RX350 set at 70 mph. I was passing someone uphill and all of a sudden engine began to rev at 4,000 RPM and wouldn't seem to come down to cruising level until I cancelled the cruise control which was engaged.

I re-engaged the cruise and all was fine after that with no reaccurance. Is this something serious or just a one-time fluke?

 

I have seen that before too, but only when towing 1000 lb trailer. The transmission seems to get "stuck" halfway between two gears.

 

hm...grade logic? not exactly sure what lexus's version of it is, but i'd imagine it'd be some where along the same lines. we have that little "issue" on our 09 350 - i'd say it's normal

 

Heres what Ive observed with our RX. Going up a hill in cruise control, 70ish, the transmission downshifts to maintain the speed. As it goes over the crest, it remains in that gear and begins to decend the hill. Then when the road flattens out it upshifts and continues on as normal.

My thought is (via grade logic or whatever its called), the car senses that its going downhill and holds itself in that gear so that braking wont be necessary. I watched this happen many times on our drive through the hills of west virginia. I think I even got it to happen when not in cruise control. I accelerated up the hill, as soon as I was over the crest I took my foot completely off the gas and may have even touched the brake, and the transmission remained in 4th gear all the way down.

Were you descending the other side of the hill when this happened?

 

Mine surely doesn't it plows down hills. Mines a 04 maybe the newer ones do. The only other car that I knows does that are radar cruise control cars and the Honda minivan.