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Odd Shifting from start: 2-1-2-3-4 (4T65E-HD)

tigers2007

tigers2007

New member
2000 Impala 3.8L 4T65E-HD

When slowing down to stop (red light, stop sign, etc.) I don't hear or feel any abnormalities. When I take off, the trans will begin in 2nd gear immediately kick into 1st gear (I feel a strong kick) and then shift normally to 2nd, 3rd, 4th, etc.

Please note that this problem happens more often when the transmission is warm (i.e. hot summer day or extensive driving).

I know this is a trans issue because if I manually shift it (1,2,3,4) the trans shifts fine. This has been going on for a couple years when I received the car. The fluid is clean. No check engine lights.

Anyone heard of something like this? Could this have anything to do with "OEM boost sleeve assembly wearing"?
 
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There is a valve in the channel plate, the large casting under the valve body, and it is known on rare occasions to stick or the bore wears and can cause intermittent 2nd gear starts. It is called an AFL valve. I havent run across this yet but have read of a few other techs stumbling into this problem and it is a posted problem in one of my books. Unfortunately it means ripping half of your trans apart to get to and you may not even see a problem with it. Since it has been going on for so long I would suspect that or a valve body cross leak, bad gasket, pressure problem, etc. No quick easy answer to your problem but likely an involving fix.
 
Mine did this in winter time when it was really cold (believe it or not I paid attention to the occurrence and it had to be less than 40* for it to do so). If I started the car from after sitting all day like from having been at work, then took off, it was like you were taking off in second gear.

However, if I turned it on, let it warm up a few minutes, then turned it off and then back on, it seemed to be okay and would run perfectly. It had to be warmed up though, otherwise it was pointless.

However, when I tore the tranny apart I dont remember noticing any wearing or anything like that on the AFL valve, but I think there was one valve in the channel plate I have not been able to get out. I'll have to check that out today because that was on thing I was curious about when I started the tear down.
 
Hi all

I'm new to this page as of today. I just recently bought a 2004 Grand Prix GTP. Love it, she drives nice. Noticing though, this problem seems to appear in our car.

If you slow down, allow her to downshift, and then not come to a complete stop and accelerate, once she's warm she does it all the time, it tends to slam or upshift harshly.

If you simply go from a complete stop, she shifts perfectly. Naturally, manually shifting her works great too. I checked fluid levels/color, all is fine.

I just took it to Pontiac yesterday, they claim it's normal.

Is this normal or a known issue that I will end up having to rebuild my tranny down the road. I have a year remaining on my warranty as I bought it used as a GM certified vehicle with only 24,000 miles in March, she now has 29+K on her.
 


While in manual or tapshift mode it will likely act like this. The pcm will command downshifts based on throttle % and vehicle speed regardless of what manually selected gear you have, and the downshifts can be a bit harsh on the tapshift transmissions when the pcm has to do the work for you. If the car is in D range then it should never take off in 2nd gear from a dead stop and then as you accelerate from the stop drop back into 1st.
 
A "slamming" transmission cannot be normal. Especially with 29k miles. Admittedly, my pImapala was used as a police car and I drive it no different than the previous owners. It is still odd though. If I manually downshift to 1st, accelerate to about 2000rpm and then put it back into Drive - everything goes smooth as silk.
 
Which is why I'm asking on this board if others experienced this or if it's a known issue.

It doesn't sound too normal to me either, and I'm trying to do some preliminary homework here to make sure I position myself for the time this thing craps out on me.

As mentioned, I just got her in March, so, I would assume the dealer would have gone through it (as it's a certified GM vehicle), but not sure if they flushed out the tranny or not, so that will certainly be my first step here, maybe it's a simple fix and I'm just being skeptical.
 
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