What could cause soft shifts suddenly?
09-14-2010, 08:38 AM
#1
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What could cause soft shifts suddenly? Brief background: 2000 A4 Z28 with tune, line pressures have been bumped up for firmer shifts, I have had the tune for about a year now.
I just replaced a bad O2 sensor about a month ago, but I think I may have an exhaust leak yet which may be causing or magnifying this issue.
Yesterday I ran a guy at a set of lights, some turbo'd Mazda something or other, he was blowing waste gate whistle at me for about three miles so I finally let him have it...after getting off the gas I came to a complete stop and did a U turn and came to a red light where the car did this lurch...lurch...stall. So i fired it back up and as soon as I would put it in gear it would stall again, did this three times, finally on the fourth try and with my foot off the brake it went into gear and was fine the rest of the evening.
Skip to this morning, drove it to the gym and all seemed pretty normal. I leave the gym and immediately noticed that the shifts at any throttle position were as soft as I have ever felt.
Did I break something in the trans, my first thought was either the converter or the pump.
OR
Is the trans in "limp mode" because of what the PCM may be seeing from the O2 sensor due to a possible exhaust leak?
I just replaced a bad O2 sensor about a month ago, but I think I may have an exhaust leak yet which may be causing or magnifying this issue.
Yesterday I ran a guy at a set of lights, some turbo'd Mazda something or other, he was blowing waste gate whistle at me for about three miles so I finally let him have it...after getting off the gas I came to a complete stop and did a U turn and came to a red light where the car did this lurch...lurch...stall. So i fired it back up and as soon as I would put it in gear it would stall again, did this three times, finally on the fourth try and with my foot off the brake it went into gear and was fine the rest of the evening.
Skip to this morning, drove it to the gym and all seemed pretty normal. I leave the gym and immediately noticed that the shifts at any throttle position were as soft as I have ever felt.
Did I break something in the trans, my first thought was either the converter or the pump.
OR
Is the trans in "limp mode" because of what the PCM may be seeing from the O2 sensor due to a possible exhaust leak?
09-15-2010, 11:08 PM
#4
May have screwed up the forward sprag.
The lurch...lurch ...stall might have been because it was stuck.
Then it unstuck and is slipping now.
Just a wild guess.
Does it slip under load in OD?
Are the shifts firm when manually shifted?
The lurch...lurch ...stall might have been because it was stuck.
Then it unstuck and is slipping now.
Just a wild guess.
Does it slip under load in OD?
Are the shifts firm when manually shifted?
09-16-2010, 08:24 AM
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I will have to try manually shifting it tonight after work to see...
It does slip under load in OD I think...I noticed it as soon as I hopped on the freeway the day everything went to hell...and I got off on the very next exit and had it loaded on a flatbed. The reason I say I think is I wasn't paying attention to how many times it shifted when I got on the freeway BUT I was doing maybe 55-60 and I was pushing over 3k on the tach. At that point to me it felt like the power was just not getting to the ground, it wanted to go faster but something just was not grabbing enough...
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09-19-2010, 02:41 PM
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Ok...drove it around the block a few times yesterday to do some more "testing" this what I found, when cold it would shift from park into reverse and both drive and OD gears just as firm as normal, but 1-2, 2-3, and 3-OD were still extremely soft.
The converter still locks up just fine...
Jays: shifts are no different if I try to shift manually...still soft
As it warmed up the shifts got softer, and I noticed a noise that followed the engine's rpm that sounded similar to when you were young and put a baseball card in your bike spokes... and it would pulsate just before shifts.
Pulled it back into the driveway and noticed the noise continued even when in park and neutral.
Didn't bother dropping the pan as I could tell from the dipstick that the trans fluid was dark brown, smelled slightly burnt but I have smelt way worse trans fluid before.
The noise sounds like it is coming from the front section of the trans, almost form the bell housing, to me with my limited knowledge of the auto trans is seems like the pump is going bad...does this sound like an accurate diagnosis???
The converter still locks up just fine...
Jays: shifts are no different if I try to shift manually...still soft
As it warmed up the shifts got softer, and I noticed a noise that followed the engine's rpm that sounded similar to when you were young and put a baseball card in your bike spokes... and it would pulsate just before shifts.
Pulled it back into the driveway and noticed the noise continued even when in park and neutral.
Didn't bother dropping the pan as I could tell from the dipstick that the trans fluid was dark brown, smelled slightly burnt but I have smelt way worse trans fluid before.
The noise sounds like it is coming from the front section of the trans, almost form the bell housing, to me with my limited knowledge of the auto trans is seems like the pump is going bad...does this sound like an accurate diagnosis???
