My 06 (104,000 miles) has started shifting erratically the last few days. Not sure if it's the cold or what. When coasting down a hill if I press the brake the car down shifts and the rpm jumps up to 3500. (most times) It's also shifting too early or too late at times. It's shifting smoothly and doesn't feel like its slipping. No dash lights are on... Could it be a sensor?
Anything I can try before taking it in for a transmission flush?

 

Do you have it in PWR mode? If so, it keeps the revs high for better throttle response.

 

Yeah I agree with speedkar, sounds like normal transmission behavior

Regwrdless, it probably would be a good idea to get your transmission fluid flushed or do a few drain/fills

 

No, it's in normal mode. Actually staying in gear longer/later than sport mode. It wasnt doing this when I bought the car. It's shifting at weird times and not staying in the proper gear.

There doesn't seem to be any issue when in manual mode.

Does this sound like fluid, or something else?

 

You need to look at the transmission fluid. My guess is its nasty, filthy dirty stuff that's overdue for a change.

 

Could the MAF or another sensor be the cause? Reason I ask, is I ran the car all day in manual mode and there were no issues. Put it in regular auto and the shifting and rpms are erratic.

No dash lights, but going to take it to autozone tomorrow to see if any codes come up.

I'd hate to drop $300 on the fluid exchange and it not be the problem when I could try something else first.

Appreciate all the info!

 

Costs nothing to remove fill bolt, stick finger in there, see what comes out. SMH

 

Even if it isn't the main issue, it should definitely be done. That being said, my IS250 did shift a whole lot better when I changed the fluid, and the the stuff that came out was really dark at only 86k even though its supposed to be lifetime fluid.

 

The old fluid probably isn't the cause of your issue, but you're going to get damage to your tranny if you don't get new fluid in there, and $300 for new fluid is better than $4500 + labor to replace your transmission – and at 100,000 miles, you may well be approaching the point where your tranny fluid is losing its ability to protect the components and dissipate heat.

As for the erratic shifting/RPM, I have seen threads where members had tranny issues that were the result of defective transmission ECUs. You may want to look up those threads, since it apparently wasn't an easy thing to diagnose. I remember at least one thread where the dealer replaced the transmission, and only figured out that the issue was the ECU when the problem came back after a few days.

 

I plan to do the ATF exchange, not trying to avoid it, I just want to get to the bottom of this. (Don't want to spend $300 to do the exchange, then find out the pan needs to come off to replace a solenoid or something like that)

Here's a new breakthrough... I put the car in Manual mode, but left it in 6 so the computer would do all the shifting. Car shifted fine up and down. No hiccups at all... Has to be some kind of sensor or control module???

Side question, is it okay to drive like that until I get this figured out? I read a thread on here that said its the same as having it in D.

 

Ah I see. Well the fluid flush replaces all 12 quarts in the transmission and the pan only holds 3qts, so you wouldn't be spending the $300 for nothing if you got it done now and then needed to take off the pan. And if you're at all mechanically inclined you can do the fluid yourself, and then it's only around $120 for 12qts.

However, it doesn't sound like your problems are mechanical. Could be a sensor fault, but it sounds to me like a problem in the transmission ECU, or maybe another computer module – ABS input can affect tranny behavior, for example. Hopefully you'll be able to pull a code that will give a better idea of what's going on.

And it should be fine leaving it in S mode, 6th gear.

 

Thanks. I'll report back with codes. I'm a single dad with high anxiety. Things like this wreck my brain when I'm on my own. Greatly appreciate all the help and feedback from everyone!

 

So many questions..
Have you changed anything recently? Fuel? Has your spark plugs been changed recently? Did this issue start after re-fueling? You may be running on less than 6 CYL.. Rough shifting or shift points that are "off" could be the engine is down on power and the transmission shift points are off due to mis firing. No codes does not indicate that the issue is not engine related. Is the idle lower than normal? Park the car, start the car, hold the RPMs at 1500 do the engine RPMs flucuate?

Check the simple things first!

 

Also, disconnect the battery (+) for about 5 to 10 min.. Re-connect, then drive slowly for about 2 to 3 miles..

 

Yep that makes sense, though the fact that you chose "Hanxious" as your username kinda told us a lot already!

And pbxcomm brings up a good point, it wouldn't be a bad idea to post up any recent maintenance, particularly if you replaced something with non-OEM parts. If it continues working properly in S mode though, that's probably a good indicator that the etiology is electronic rather than mechanical.