6l80 1-2 hard shift

apollo18 · September 5, 2017

i got a 2007 escalade with a 6l80 (still gm ahah). the transmission was replaced about 180km ago. the truck right now has 320,000km on it.

The transmission has a problem and its had it for a while. the transmision was put in brand new around 2010/2011. The problem has been happening for atleast two years and its annoying. I hate taking it to gm because they charge a ton and then just tell me to replace the tranny.

Now to the problem:

The truck has a hard 1-2 shift, and a semi hard 2-3 shift. The 2-3 shift is ok. I only have a problem with the 1-2 shift. The truck basically thuds into a shift only for the 1-2 shift. The 3-4,4-5,5-6 are SUPER SMOOTH. its a 6l80. I had the fluid changed a couple times, that didndt fix it. I just got the whole fluid flushed with a new filter and that made the shift a little more smoother but the 1-2 is still a thud. What i noticed is that when I have the battery unplugged And then I plug the battery and drive. The transmission shifts smoothly. Last time I had to unplug the battery and drove the truck after i thought the problem was fixed but it came back after a day or two i cant remember. The 1-2 shit is hard no matter what, even with WOT, or manual or slow speed. I read around and i thought it was the TPS so i replaced that. No go, also replaced the MAF to fix a engine code, and then I read around and some people said Camshaft position sensor so i ordered that and will put it in once its here.fluid level is fine in the truck. Other then the 1-2 hard shift, the truck run's fine. i just wanna fix the hard shift. I believe its a sensor or something electrical because it seems to go away when teh truck has no battery. but then it comes back after a day or two. The 3-4,4-5,5-6 shift is ALWAYS SMOOTH. once again the 2-3 shift is bearable its a light thud but not that noticeable so im happy with it.

Truck has stock ecm and tcm. Here are some codes I pulled a couple months ago from a bully dog. Maybe they will help?

P2700 Transmission Friction Element A APPLY Time Range/Performance

P0100 Mass or Volume Air Flow Circuit (should be fine now after MAF change)

P0500 Vehicle Speed Sensor A

P0200 Injector Close/Open

P0700 Transmission Control System MIL REQUEST

P1500 Vehicle Speed Sensor VSS Intetermittent

and then a bunch of unknown ones too

any help?

thanks

newdude · September 5, 2017

I think you need a transmission guy with those codes. However, that Bully Dog pulled some non existent codes. The only two codes that came up in GM service docs were the P0700 and P0100. Need a much better scan/code reader.

sdeeter19555 · September 5, 2017

Take it to Advance Auto, they have a pretty decent code reader and scan for free. They won't get them all, but they get more than the average code reader.

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Swimmer8366 · September 5, 2017

Where you from I got a Transmission guy....

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Justin101714 · September 5, 2017

If your ISS and OSS don't correlate. You will have line pressure issues. Basically the TCM is defaulting to higher than normal line pressure because the input speed sensor and the output speed sensor aren't meshing quite well. Could be multiple causes for this. But, what I do to verify speed sensor operation is use a variable signal generator at the harness connector the sensors and see if the scan tool data is responding to the change in signal. This would verify if the sensor is bad or if the TCM is bad. You could also have a circuit issue between the TCM and the sensor.

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apollo18 · September 5, 2017

ohh im from alberta canada btw and ill use a better code reader first and get back to you guys. If TCM is bad then its a $1000 repair no?

apollo18 · September 9, 2017

my bullydog has always been iffy with finding codes. sometimes it displays them sometimes it finds none. i tried with vehicle off, vehicle on, key in run and it didnt show anything. i tried two days in a row. so then i went out and bought a autolink al419 but this code reader only shows me two codes that i dont really cara bout

P0308

P0455

i restarted truck and tried twice but only two codes. I usually get way more on bullydog(when it works) and bullydog is where i got the VSS one. This code reader was $150 CAD should be good enough.

I dont have any advanced auto or o reillys here so i cant get them to check codes.

What i did is erase the codes tho and ill unplug the battery and then check after a couple days to see if any come back?

Justin101714 · September 10, 2017

Just let us know. When you erased the DTC's, did the shifting change?

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cashflow50 · September 12, 2017

where is the TCM located? i have a similar problem with the hard shift. thanks

apollo18 · September 13, 2017

So when I first scanned codes last week I was only getting two codes

P0455 which I've been getting for like 2 years

P0308 I've had this for a while as well

I then unplugged the battery for a couple mins and the shift improved a lot, it's just a slight thump! Then after a day or so, it went back to the hard shift.

Over the past couple days I've tried to scan codes again with both my bulldog and al419. The bullydog isn't showing anything and the al419 only shows

P0308

And p0455

Do I need a better scanner? My bullydog is a hit or miss, when it does finds codes it usually finds a lot

apollo18 · September 22, 2017

got a gm mechanic to look at it, he reset it with tech 2 and now its smooth as butter. every single shift. hes gonna look into the codes and let me know.! seems like its gonna be a small problem/sensor since it went away temporarility with a reset?