Tranny down shifting on highway

[BlazinTBlzr]

Anyone have this happen, cruising along at speed and all of a sudden the tranny shifts down a gear and revs the engine. Very intermitent but aggravating as all get out. Obviously the dealer has no clue.

[2002SLT]

Are you going up a hill, or towing something when this happens?

[BlazinTBlzr]

It has happened towing and not towing....

[ylab]

Are you sure it down shifted and didn't simply unlock the converter? The TQ converter can lock and unlock due to a variety of conditions, just a thought.

[ScarabEpic22]

No, it doesnt downshift, and the PCM is still commanding the TC to be in lockup state. I have this issue and have done some long term logging of trans state, pressure, TC state, etc. and havent figured it out.

I think it probably has something to do with internal parts that I cant figure out.

[BlazinTBlzr]

Well that just plain stinks...no answers uhh..
Not that familiar with what you guys are actually saying other than something is not right. What is the effect of this long term then to the tranny?
I mean it seems pretty aggressive as you are cruising along at 70 and the engine revs to 5k with a trailer in tow...

[MTPockets]

I've seen this exact issue happen on the GM 4L30E (isuzu rodeo and trooper) and it is the range/mode sensor that causes it on those. The range sensor is a wiper/contact type switch attached to the shift arm on the 4L30E that tells the PCM/TCM which gear the operator has selected. Without a clean constant output from the switch the trans would shift erratically at times. Problem is, I *think* the 4L60E has an internal range sensor?:confused: A sure-fire test of a faulty range sensor on the 4L30E was the PRND321 dispaly on the dash would not match up with where you set the floor shifter. Just tossing some ideas out there!

G/luck
Joel

[BlazinTBlzr]

Thanks, maybe I will throw that at the dealer......