f4a51 harsh downshift every once in a while?

[2000izusu]

Hello all,
maybe once a day or every three days i will come off the highway and slow to maybe 25-30mph then my light turns green i go to take off and the trans downshifts to the proper gear harshly?
this has been going on for a year.

is this normal (i have heard of others with the same characteristics)?

will reseting the addaptive memory help?

this is on a 2004, 2wd, 2.7L with 75,000 miles

fluid is pink and has had drain and refills at 30,000, 61,000 and 70,000

all three drain and fills had spIII used (dealer change on the first 2 and have reciepts, third time i did myself).

i appreciate any help!

thanks,
mike
__________________
2004 santa fe gls 2.7L auto (ice blue)

[DSHornet]

Originally Posted by 2000izusu

will reseting the adaptive memory help?

What the heck, why not try? Can't hurt.

[rodeo02]

You've definitely kept up on your ATF drains/fills. Have you checked ATF level just for grins? This is a tough one given you don't have any other symptoms like a CEL. If you recall the old transmission range sensor days (Isuzu Rodeo 4L30E), our F4A51s have them as well. A dirty TRS can fake the TCM into thinking it's not in the right gear. Normally you'd get a CEL or your PND321 would flash at random on that. Just tossing some stuff out there!

Joel

[2000izusu]

thanks! the range sensor is something to investigate. i am going to try the addaptive reset this weekend. i got my fingers crossed.

is your downshifting smooth as can be? or does your f4a51 feel like it doesn't know when to downshift sometimes? mike

[rodeo02]

Mike, the only time I've noticed mine bang down pretty hard is when I've got the whole family in it (5 total). Other than that, the shift points are great and super smooth.

Joel

[2000izusu]

well i finally got to the addaptive reset 5 days ago and since then not one harsh down shift! feels like a new transmission.

i guess i reset it to factory presets? and as i drive it will learn a new preset? anybody got any explanations? mike

[rodeo02]

I can confirm clearing the shift adapts does work. I had an issue with the 4T45E in my 2007 Cobalt where it would oscillate out/in/out/in of TC lockup until you changed throttle position. The car was still basically new at the time. The only fix GM had at the time was to clear the learned 'adaptive shifting'. They did that and the problem went away. I thought killing power to the ECU/TCM did this, but apparently it requires a more advanced dealer scanner of some sort.

Joel

[2000izusu]

the previous behavior of the harsh shifting was from the old owners addaptive learning. i was under the impression that it would "learn" to the new owner (my family). but a family member drove it 5000 miles and it never happened. so i did the addaptive reset, and it is good so far. i will post an update as the weeks grind on, about how it is still shifting! mike

[2000izusu]

Originally Posted by rodeo02

I thought killing power to the ECU/TCM did this, but apparently it requires a more advanced dealer scanner of some sort.

Joel

it might require special equipment on a 4t45e? but on most a simple battery disconnect will not do it, as you mentioned.

i understand what needs to take place is: a draining of the capacitors in the pcm/tcm to get rid of the "learned" behavior, in addition to the battery disconected. mike

[2000izusu]

well it has been a month and the problem has not come back! i think we can call it fixed. mike

[rodeo02]

Good deal Mike. Mine's been shifting as smooth as butta for the last since I changed the ATF to Maxlife (4K miles ago). I can't get over how awesome the thing is in the snow as well.

Joel