2003 T6 slow to downshift. May be the old trans fluid.

[Cees Klumper]

My 2003 T6 automatic while driving at say 50-55 MPH recently started to stay in too high a gear (4th) when it should be downshifting, for example when climbing a gradual hill. If I depress the accellerator a bit more, it still won't downshift like it used to. Only when I really floor it so as to 'command kickdown' OR, (and this is the odd part), when I just 'blip' the accellerator pedal a bit deeper than I'd normally want to, the transmission downshifts like it should. Forcing kickdown isn't really pleasant and should not be necessary, nor should the 'blipping the throttle' method. I checked for codes and there are none. Other than this shifting behavior, the car runs like a dream.

I was thinking, could this be caused by my throttle position sensor starting to go on me? Or do you think it's something else? The trans shifts supersmooth and I've not noticed any other issues with it. It's never had the trans fluid replaced, still original with about 135K miles on the car.

[oragex]

I had the same and it improved with new fluid. I believe you have the GM transmision which uses Type III-G Dextron fluid . Don't let a garage 'flush' the transmission, it will damage it. Instead, see this forum.

You may want to do this in 2-3 steps rather than all at once, passing each time about 5 liters of fresh fluid, then drive for about 1000 miles, and repeat.

http://forums.swedespeed.com/showthread ... sion-flush

[Cees Klumper]

Many thanks, will renew the fluid after duly studying all the advice and experience here. According to my information I should have the 4T65EV-GT but will double check that as well. Will report back when done.