2011 tahoe first gear issue

[jhous09]

Sucks man, sorry to hear...I taught myself how to rebuild transmissions when the same thing happened to me when I was a teenager. Do you have a scanner capable of pulling/reading transmission-related DTCs?

Neutral in first could definitely be the sprag beginning to slip. I replace those each and every rebuild w/a GM AC Delco sprag assembly (Sonnax also makes a rebuild kit for them but I've never used it) - the assembly is around $125.00, not $500. I also replace the snap ring holding that spring in position on the back side of the center support on each overhaul (wonder if that was done at all).

If the TEHCM's fluid pressure switches are the problem, you're looking at TFP 1 as the possible culprit. If it's intermittently failing then you'll get a 'false neutral' condition in first gear followed by the transmission 'slamming' into gear. As @swathdiver mentioned, the diaphragms can sometimes either brake or get clogged up, impeding their ability to communicate information needed to control the transmission and they can be replaced on the bench w/the TEHCM out. Transgo sells a seals and diaphragm kit for those transmissions. The TEHCM should have been replaced with a compatable OEM TEHCM replacement unit.

Swapping in a Salvage Yard transmission:
You MUST verify that the TEHCM part number matches the part number on your TEHCM or have the TEHCM in the replacement 6L80 reprogrammed to match your vehicle's OS. If you don't do this, the replacement trans will never work right. You'll then need to do a fast adapt relearn to re-set the adapts to factory default before attempting to drive it. Go to a reputable salvage yard in your area if you're going to go this route - make sure you have a warranty so you can bring it back if it doesn't work.

You can check out my 6L80 Information thread (link in my signature) for more details around what parts and procedures need to accompany any rebuild of those units.

How do you do the fast adapt relearn? I do have a scanner that can communicate with the transmission and it never sets any codes.

 

[NickTransmissions]

How do you do the fast adapt relearn? I do have a scanner that can communicate with the transmission and it never sets any codes.

What scan tool do you have?

 

[jhous09]

This is often a problem with the TECHM solenoids that you can rebuild on your kitchen table without removing the transmission from the vehicle. That's what I think but let's ask our resident expert, Nick. @NickTransmissions

Supposedly the techm has been replaced twice from the builder. I have no way of verifying if that is actually true

 

[jhous09]

What scan tool do you have?

Autel ms906 pro ts

 

[NickTransmissions]

Autel ms906 pro ts

That scanner is capable of doing anything you'd want to do on a car/truck/suv trans using a scan tool. I use all SnapOn scanners so if you're not sure how do the fast adapt on the Autel there's prob a few good YT vids available to bring you up to speed.

 

[jhous09]

That scanner is capable of doing anything you'd want to do on a car/truck/suv trans using a scan tool. I use all SnapOn scanners so if you're not sure how do the fast adapt on the Autel there's prob a few good YT vids available to bring you up to speed.

My scanner doesn't give me the option to do the fast relearn just reset

 

[Gearz]

Sorry about your troubles. If I said once I said it a thousand times. Why do people have a trans rebuilt. Use a GM remain and pay one time then it has a 3 year warrant. I made this mistake back in the 90’s for my truck that had an intermittent shudder that no one could find so I bit the bullet and put a GM reman in it. The problem with mine was a faulty torque converter or leakage but it cost me more in the long run. I will never have a trans rebuilt again. All GM remans also come with the latest updates which solve most issues Like valve body’s etc….

 

[alpha_omega]

Sorry about your troubles. If I said once I said it a thousand times. Why do people have a trans rebuilt. Use a GM remain and pay one time then it has a 3 year warrant. I made this mistake back in the 90’s for my truck that had an intermittent shudder that no one could find so I bit the bullet and put a GM reman in it. The problem with mine was a faulty torque converter or leakage but it cost me more in the long run. I will never have a trans rebuilt again. All GM remans also come with the latest updates which solve most issues Like valve body’s etc….

The only problem with a GM reman is that they only use GM parts, which most of the time is exactly what you want. However, some of the transmission components that GM makes are of “less quality”, especially when you consider any aftermarket components someone may have added - the torque converter being one of these items that needs to be properly welded prior to installation and the other being valve body. Granted these parts may not necessarily NEED to be replaced, but if not you run the risk of another rebuild sooner than expected.

 

[jhous09]

@NickTransmissions is there any way to get the Transmission unique number to program the techm other than the side of the transmission?

 

[NickTransmissions]

@NickTransmissions is there any way to get the Transmission unique number to program the techm other than the side of the transmission?

Not that im aware of but perhaps there's a way to look it up in GMs online diagnostic web interface but that's just a wild ass guess.

Best way is to look at the tehcm itself...