Hey guys,

So about 2,000 miles ago I installed a magnaflow y-pipe back exhaust and cleaned my MAF sensors. 2007 with 40,000 miles. When it's in "D" now it will shift 1st ---> 2nd and 2nd ---> 3rd perfectly at low speeds (shifts into 2nd at 9MPH and 3rd at 18MPH). Now if I keep this constant amount of throttle the 3rd ---> 4th shift is awkward. Right at about 21 or 22MPH it feels like the car shifts (doesn't) then it shifts into 4th at 25MPH like usual. In that period of time at 22MPH the revvs drop about 200RPMs and it feels almost like the torque converter is locking... It is impossible to replicate this in manual mode and if I give it more throttle you would never even know it was there in "D"... It must be electronic I'm thinking since I disconnected the battery to do the work, and it was there first time on the test drive. I reconnected the ground wire to the magnaflow and allowed the MAF sensors to dry completely. Any input? Drives me nuts to the point where I drive it in "M" all the time now, it's perfect when I shift it, but it should be even more precise on its own.

Cliffs:
40000 miles HR
Installed magnaflow and cleaned maf sensors
Reconnected battery and took for test drive
tranny shifts weird in "D" but perfect in "M"
allowed over 1000 miles to relearn itself, but never helped

Also, fluid level is spot on at 149 degrees F and I have changed it religiously (at least a drain/fill every 5,000 miles)

Thanks!

 

I don't know anything in depth about autos, but if you are draining and filling your tranny every 5,000 miles, that's not necessarly a good thing.

It has been my experience with past cars, and of people i know, that if it ain't broke, don't fix it, when it comes to fluid changes in auto trannys. When you drain the fluid it tends to "dislodge" crap that has built up in the lines that would otherwise gradually make their way to the filter. Normally dislodging crap would be a good thing. But the passages in your tranny are so small, it only takes a small speck of junk to clog one up and cause erratic shifting. That's why i walked out when i took my beater to the Chevy dealer to price a tranny fluid change and they told me they "back flush" it through the filter (I.E. pushing all the crap the filter has trapped over the years, back through the tranny!). So i determined that my fluid is still red, doesn't smell burnt and the car shifts fine so i just let it be, even with 145,000 miles on the clock and no idea when or if it was last changed. I also towed a boat with my cavalier for two years on this same fluid, so the car doesn't get babied.

 

There was a shifting issue the auto g37's had. Forgot exactly what it was but it can be rectified at the dealer. its a minor adjustment

 

that is your problem right there. totally uneeded with this tranny

 

+1....that's overkill

 

wow.. auto fluid every 5k miles.. spendy and overkill.

 

Don't listen to any of the above folks. Changing the ATF regularly with a drain/fill is the BEST thing you can do for your transmission. Unlike flushes, there is no dislodging of debris that can occur as one poster mentioned. If you keep the ATF fresh and keep the trans cool, it will last. That said, unless you are tracking the car or you are FI, 5k is probably overkill and you are throwing out good ATF. It won't hurt anything though. I change mine every 6-8k (every other oil change), but I'm pushing nearly 500 wtq through it every day.

What you are describing sounds like the torque converter locking up. This is most prominent in my car on the 5th gear lock, but 4th will also lock. A clutch plate will lock the TC for greater fuel efficiency in 4th and 5th gears (as per the FSM). I don't think you have anything to worry about. Just make sure you check ATF fluid levels as per the FSM procedure (car warm to hot and running, dipstick reversed, etc).

 

As I said before it is NOT a fluid related issue, it happened only immediately after I unplugged the battery and cleaned the MAF sensors and put on an exhaust. It is the most perfect automatic transmission I have ever driven while in manual mode. New fluid every 5K is not expensive to me to make it last. 4 quarts from my dealer is roughly 40 bucks with tax and that is more than worth it to me to make it last. Also, as stated, I read out the fluid temperature at 149 with my computer using the autoenginuity scan tool to verify correct level, so again, this has NOTHING to do with the fluid. So, on that note, any other suggestions? It is electrical or computer related, so what could it be?