10L80 not shifting p0777

[k_arnold72]

2018 Tahoe with 6.2L and 10L80, 197k miles. First sign of an issue, I was accelerating on the highway and it felt like I instantly dropped into neutral, just a full loss of traction. A few yards down the road, I'd regain traction. That happened twice about a month apart. No transmission related codes. My last transmission fluid and filter change was 45k miles ago, and I drive pretty hard, so I'm due for anther change.

Recently, I was coasting to a stop, felt a jolt, then when I began rolling again, transmission wouldn't shift.

Now I'm getting code p0777, valve body solenoid b stuck open, and a tcm related code, u0101. I pulled the pan and there's minimal shavings on the magnet, no chipped gears or anything that strikes me as major damage.

I've reached out to various local dealers and transmission shops, and there seems to be a long lead time for a new valve body. So I'm looking for repair/replacement options for a valve body's solenoid(s).

 

[pronstar]

Personally, I wouldn’t go back to stock…

10L80-E Transmissions & Transmission Parts

Next Gen Drivetrain™ is committed to engineering, developing and manufacturing the highest quality General Motors 10L80-E transmissions and transmission parts. All of our products are designed to optimize for reliability and quality, maximizing shift quality, longevity and performance for all...

nextgendiesel.com

 

[k_arnold72]

I'm exploring all options. If they have units in stock, I'll def reach out. Thanks

Personally, I wouldn’t go back to stock…

10L80-E Transmissions & Transmission Parts

Next Gen Drivetrain™ is committed to engineering, developing and manufacturing the highest quality General Motors 10L80-E transmissions and transmission parts. All of our products are designed to optimize for reliability and quality, maximizing shift quality, longevity and performance for all...

nextgendiesel.com

 

[k_arnold72]

@NickTransmissions I have hptuners and an unlocked tcm, what's the next step in figuring out where my issue is? I've tried flushing the fluid, which worked for one guy on YouTube. But after the most recent test drive, it's still stuck not shifting.

I've also picked up a new genuine gm tcm from rock auto and can confirm that the truck can't read what gear it's in without programming. I even did the procedure that Matt Sanford showed for installing a tcm, but the new one was still not being read. I swapped the old tcm back in and I'm back being able to at least shift from gear to gear. I'll try a relearn and see how that goes.

 

[NickTransmissions]

@NickTransmissions I have hptuners and an unlocked tcm, what's the next step in figuring out where my issue is? I've tried flushing the fluid, which worked for one guy on YouTube. But after the most recent test drive, it's still stuck not shifting.

I've also picked up a new genuine gm tcm from rock auto and can confirm that the truck can't read what gear it's in without programming. I even did the procedure that Matt Sanford showed for installing a tcm, but the new one was still not being read. I swapped the old tcm back in and I'm back being able to at least shift from gear to gear. I'll try a relearn and see how that goes.

I haven't actually begun working on the 10 speeds for GM and Ford as of yet but planning to start this fall. That said, I'll have to take away the above and research it a bit. See if there's an obvious solution(s) that don't involve a full overhaul. False neutrals are usually indicative of internal-to-the case mechanical failures however in the eight and 10-speeds, they can be valve body, solenoid and/or TCM related. We would want to start with the easiest / cheapest causes first then rule them in/out before thinking about pulling the transmission.

I'll reply later today or early tomorrow with something...

 

[k_arnold72]

Thanks! I read somewhere else what the family of _L80 transmissions might all use the same solenoids? I skipped work and checked a couple local salvage yards today, but no luck finding a donor.

So I think the next cheapest solution would be to keep looking for a used transmission to salvage a solenoid from. After that, the Sonnax or Next Gen rebuild kits. But that would be assuming the solenoids are functioning electrically and my issue is mechanical.

For now all I can do is drain the fluid again and disassemble my existing valve body, and individually test the solenoids.

I haven't actually begun working on the 10 speeds for GM and Ford as of yet but planning to start this fall. That said, I'll have to take away the above and research it a bit. See if there's an obvious solution(s) that don't involve a full overhaul. False neutrals are usually indicative of internal-to-the case mechanical failures however in the eight and 10-speeds, they can be valve body, solenoid and/or TCM related. We would want to start with the easiest / cheapest causes first then rule them in/out before thinking about pulling the transmission.

I'll reply later today or early tomorrow with something...