Random Harsh Shifting in First and Second gear

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Alpha Mike Sierra

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I am the second owner of a 2016 Tahoe LTZ with 135k mi that started to have random hard shifts when in first or second gear. Most often this occurs after a firm stop and take off (not a launch) from one of many stop signs around my house.

Sometimes after coming to a full stop the truck will lurch forward like someone hit me from behind. Every once in a while shifting from first to second it will be very firm and chirp the tires at around 3000 rpm.

Carfax says the transmission was replaced in 2018 at 90k mi.

The transmission was recently flushed when the truck was at the shop for an AFM/DOD delete. The trans filter was changed and fluid was clean with no contamination.

This is my daily driver and about a dozen times a year tows a 7000# trailer for camping trips.

Any ideas? Is this the torque converter talking to me?
 

B-train

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How long has it been since the work was completed? It takes a few drive cycles to learn your habits. If it was very recent, then I'd speculate it may need more time to see if it corrects itself.

Otherwise, maybe the torque converter is going out. What does the trans run at for temp? Has the new thermostat valve been installed?
 
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Alpha Mike Sierra

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Yes, I forgot to mention the transmission valve was updated with the flush. Prior temps were 180+ around town to 220+ when towing. Now it is around 150. I have put almost 1000 miles on it since the flush and valve update. I haven't towed with it yet since it has been raining all winter here. I am also a little nervous about loading this powertrain up right now...
 

NickTransmissions

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Yes, I forgot to mention the transmission valve was updated with the flush. Prior temps were 180+ around town to 220+ when towing. Now it is around 150. I have put almost 1000 miles on it since the flush and valve update. I haven't towed with it yet since it has been raining all winter here. I am also a little nervous about loading this powertrain up right now...
Did you end up getting this resolved?

If not, it could be throttle position sensor, MAF or tcm’s interpretation of tps data streams. Input and/or output speed sensor can also be intermittently failing…it could also be the TECHM itself…Those are a few examples of command/control sources for sudden odd/erratic shifting patterns observed by the driver.

Is the CEL on/any codes stored in the PCM?

Did the shop run a “fast-adapt” reset or any other programming after completing the flush/replacement of the valve and AFM delete?

Did the shop comment on the fluid’s appearance, presence of contamination / material or smell at all?
 
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Alpha Mike Sierra

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Still working on this issue. Now it is showing a P0340 code intermittently. Getting a new camshaft position sensor tomorrow.

I will ask the mechanic any stored codes.

The AFM delete kit came with a Diablo tuner to reprogram the ECM.

The fluid had no discoloration, no smell, the filter was clean. I will keep posting updates and hopefully have a resolution soon.
 

Miami-Dade

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Carfax says the transmission was replaced in 2018 at 90k mi.

The transmission was recently flushed when the truck was at the shop for an AFM/DOD delete. The trans filter was changed and fluid was clean with no contamination.
Out of curiosity what transmission fluid did they exactly use?
 
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Alpha Mike Sierra

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Update: The P0340 code was fixed with the new cam position sensor installation. Much more power now. It has been raining so much around here, I haven't noticed the sluggish response. I was sliding all over the place after picking it up from the shop.

Still no improvement on the lurch. Next step is to clean the MAF. Any chance removing the battery and fully grounding the electrical system resets the TCM? Any chance grounding is harmful?
 

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