Weird shifting issue - Need some creative input
 

Hey guys, I have the strangest thing going on with my 2005 4.4i tranny.... I started with the 1st to 2nd gear "slam" which I corrected by dropping the trans pan and replacing the mechatronic seal adapter and 4 pick up tubes, I also installed a new filter and 6 quarts of pentosin while I was in there.

Again, 1st to 2nd gear "slam" is gone but now I am left with the dreaded harsh 2 to 1 downshift and she seems to "bobble" just a little bit on the 1 to 2 upshift.

I took it out to my local dealer and had them do the EGS flash to the latest software which resulted in no change.

What am I missing? Shifts are a million times better but still just not spot on...

Thanks!!


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How much mileage on the truck, and what kind of other previous AT repairs and maintenance (if any) have been done?

I have a 3.0i, which has a different AT (GM vs. ZF), so I can't comment specifically. But when I starting drain+filling my AT for the first time ever at about 169k miles (when new to me), the first fluid D+F (with pan drop, cleaning the pan, new filter) did end up knocking a bunch of new debris loose, which I found in the pan on the second D+F a few hundred miles later. I did the 3rd and final D+F a few thousand miles after that and it has been flawless.

So if you think that data point is relevant to your situation with your ZF, my point is that you can consider the new fluid to have solvents in it that may release new debris/problems just from doing the D+F.

Thanks oldskewel, that is actually a good thought, maybe I just need to put a few miles on it and drain it again.

My history with the car, purchased at 47k miles and did first fluid change, changed again at 100k miles and at about 105k I picked up the hard 1st to 2nd shift. I babied it that way for about 500 miles, would just let it warm up before I drove it and when I finally had time I pulled the pan, replaced the seals and cleaned everything. When I pulled the pan the magnets were clean as was the fluid having just been done 5k or so ago but after doing the service in an attempt to clear up the 1 to 2 hard shift I solved that and picked up this nasty 2 to 1 down shift gremlin and it's driving me crazy.

I noticed it immediately after putting it back together and test driving the car so I immediately came back, checked my fluid level and actually did an additional drain and fill to which I had no better luck...

That's when I found SIB 24 01 06 calling out the harsh 2 to 1 down shift and ran her out to be reflashed by my local dealership.

With fingers crossed I picked her and and to my dread... the problem persisted.

Since the initial fluid change I've put maybe 900 miles on it, I may give it 1500 miles or so and do another drain and fill - though I am considering buying the valve body rebuild kit and servos if need be...


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Reset adaptation? Maybe with better friction values you need to reset the clock on adaptations?

Tried that too ☹️. Actually did the key on, no start, hold pedal to the floor for 30 seconds myself (unless I did that wrong?) and asked the dealership to reset before flash as well.

I am sadly thinking I may be in for a valve body rebuild and new solenoids unfortunately as I don't think it's "in the transmission" being that my magnets were spotless and I found absolutely no signs of debris in the pan or filter when I dissected it.

That said, I may try that again in the morning before I back out of the garage. The strange thing is that it doesn't get any better or worse no matter how hot or cold he tranny is - even more so leading me to believe I have a pressure leak ☹️☹️


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