6l80 lost communication

[fast43]

ok so here it is. I have a 2011 Silverado with a 5.3 6l80. it had a 4.3 4l60 original in it. I have been running the 5.3 6l80 for over 3 years no problems. it has a laundry list of mods and up grades done to it and its N/A. 3 weeks ago the 6l80 went out on me so I took it out and found out the techm is officially bad as well as the gear rings. some of the rings in 4th gear are fused together and cant be separated. so I went and bought a verified 10,687 mile 6l80 and installed it. I drove the truck to the dealer shifting threw all 6 gears and verifying it works as it should. the dealer took it back to do the dealer flash. they told me that at the end of the flash it would kick them out and not finish the flash. no I drove it 10 miles home in first gear and hooked up hp tuners to it. in scan mode it gives me the U0101 code but in write mode it doesn't even see the tcm to do any thing with it. I'm puzzled now as to what to do with it.

[1364838952]

The problems you are experiencing are the exact reason why I despise GM and will NEVER again purchase one of their products. They have royally screwed up what was a proven, working, transmission controller with the CRAP they have pulled with the 6, and later, speed transmissions.

If it was running, and shifting, after installation why then did you take it to GM for a flash? Typically if there is an issue that would require a GM re-flash, the vehicle will only have 4th gear, and will NOT shift on it's own. If it was shifting through all gears, I would have done the Pre-set, re-set, and quick learn, with HPT and then just left it alone. But... what's done is done..

You stated "found out the techm is officially bad ".. How exactly did you come to this conclusion? Did someone test it using the Kent Moore tool to verify that there was an actual issue with 1, or more, of the solenoids? What diagnostic procedure lead you to the conclusion that your original techm was bad? That's what I want to know. Had you NOT gone to GM, you could simply swap your old valve body, along with the TCM, and the solenoids, to the new transmission and it may have worked. BUT, since GM has now tampered with it, even that may not work anymore... You could try it to see if that works. Just remove your old valve body from your original trans, separate the different pieces, verify that no valves are sticking/stuck, put it back together, and install it on the trans that is currently in your truck. Then try and drive it. If it is shifting-STAY FAR AWAY FROM GM!!!


It is my personal belief that GM IS NOT in the business of helping, or supporting, us working on our own vehicles. To advance that statement, I believe it is NOT IN THEIR BEST INTEREST to support, or help us in working on our vehicles ourselves. They are in the business of selling cars, and parts for their cars, and technical services for their cars. It would not surprise me in the least if you could PROVE that they intentionally screwed the programming up on your vehicle with the intent of you having to purchase a new trans from them. Or, they had a lower skilled technician working on the vehicle who made a mistake during the program that has now destroyed the TCM, or bricked it. Regardless, you will NEVER know the truth now. Again, avoid the dealership at all costs if/when possible. Situations like yours are just further proof that my theory of avoiding them like the plague is the correct one. I do purchase, and install, 6 speed transmissions directly from GM when the customer requests that over a rebuild, and then allow GM to do the programming on those vehicles. That way, if they screw something up-it's on them to fix it at their expense! It's amazing how they never make mistakes when it's THEIR $$ on the line, but if a customer comes in with a vehicle that they swapped a used unit into suddenly the TCM gets bricked. Funny how that works.

There are only 6 bolts that secure the VB to the trans case. You will need an inverted type torx bit to remove them. In a pinch, a bell housing bolt from a 4L60E can be used by welding a nut on the end of it. The head of the bell housing bolt is a direct fit onto the VB retention bolts. You will also need an in./lb. torque wrench to put it back together. I believe it is 71 in. lbs. on the torque spec but you may want to double check that on the web, or in the ATSG book. I'm at home right now but have the ATSG book at the shop.

[fast43]

yes I had to swap out the 2wd out put shaft from the old one to the new one because the new trans was a 4wd unit. I fully inspected the new trans when I put it all back together. I also cleaned all the parts prier to the rebuild. I also had the vb taken apart to see if it will be in good working order and it was. I admit I was in the wrong for taking the truck to the dealer to do the flash learn to the vin and should have done all the necessary steps to make it run and then do my tune to it. it sucks that I'm in this position and you are on point with me never ever going to the dealer. with that said I will be calling the dealer and looking at options for them to fix it because I do have paperwork saying I was there to get this fixed. FYI it was a Cadillac dealer that tried the flash to vin procedure on my truck that is a Chev.

[1364838952]

If you still have the VB off the original trans you pulled, install it on the trans that is in your vehicle now and see if it works. If it shifts, just do the quick learn procedure and leave it be, or tune the shift tables from there.

[fast43]

yah that original vb needs repair. one of the valves failed and the 4 pressure switches need repair. also the removeable plate with the screens has a spot were one of the screens caved in on it self. it can be fixed with the right parts to fix it though. I have yet to test the valves on it.

[1364838952]

You can pick up a new VB assembly from one of the many vendors that are remanufacturing them, or directly from GM. I pay $800+ for new valve bodies, and then I have to take the vehicle to GM to have it flashed. The new VB will come as a complete assembly with the TCM, and all solenoids, attached.

[warriorpluto]

Are valve bodies really that expensive for 6l80? I would just go with another used transmission for that price.

[DrLoch]

Yes they are, you can get remanufactured from a number of sources, Ebay for one but it's not flashed with the information for your vin. Another option that I chose to use was Dorman, https://www.dormanproducts.com/gsear...rol%2520Module. That worked for me, but you have to have a flash/tune in the TEHCM unit that can be copied and written into the reman unit. If you go with another trans you still need to go down the path of matching the TEHCM info with the VIN number. I wasn't able to find a work around for the programming issue.

[warriorpluto]

Ok one more question. If I wanted to use a 2010 6l80 in my 07 Denali I would need to take out the valve body and wiring and put into the 2010 6l80 correct?

[DrLoch]

Yes, assuming that the VB & TEHCM is good in the trans you are removing. You're gonna want to replace the seals between VB and housing. What is wrong with the original ?

[warriorpluto]

Yes, assuming that the VB & TEHCM is good in the trans you are removing. You're gonna want to replace the seals between VB and housing. What is wrong with the original ?

Nothing is wrong with my transmission right now. Just wanted to know when the time comes lol

[Vanilla bean]

I have the same problem switched my tranny from my 2012 5.3 with a used one and was shifting okay but no reverse lights no gear selector light towhaul and woudnt let me put in on 4x4 my guess its bc the truck doesn know its on neutral after a day it threw itself into limp mode later realized tht my mechanic didnt even reprogram the transmission so I took it to the dealer and they said the tcm wasnt communicating and that they coudnt reprogram it