Torque Converter or Transmission

[Just Fishing]

^ If it's just first gear, it sounds like a low sprag failure.

I'm also curious if using tow mode helps or not.

 

[Just Fishing]

Re-read this.
since you mentioned a speed that rules out first gear I searched a little.
Sounds almost like when the transmission goes into a fast learn.

Found this: https://forum.hptuners.com/showthread.php?79917-6L80E-TCM-random-disconnect-at-WOT-drops-in-neutral

Possible cause electrical!
"Power wire from the alternator that goes by the head got really close to the header and was randomly arcing"

 

[Doubeleive]

Thanks, how much should I be saving up? Last time I bought a transmission, not sure what brand, I paid 3600 for a new one with 36,000 warranty for my wife's 5 speed explorer from an independent shop. The new one went out a few weeks before the warranty expired so I really lucked out. But I'm sure it wasn't a ford tranny.

about $4k and take it to the best shop in town. a experienced rebuilder should get it done right and it will be less than what the dealer will charge.
tell them you want a billet torque converter & rebuild.

 

[Charlie207]

Every time I read one of these threads my anxiety starts spiking.

 

[Just Fishing]

Due to it going into "N" when WOT and at speed.
I'm leaning towards an electrical issue like a short/grounding issue.

These are clutch to clutch transmissions.
valve body and computer controls everything!
If the TCM was to shut down suddenly it makes sense that the cutches would release.

In the one link, it showed he was doing data logging and the data from the TCM froze when it happened.
Suggesting the TCM shut down and possibly rebooted.

I also wonder if the op also has an engine/transmission mount that failed.
Allowing the engine to rock and bam short or ground getting pulled!

 

[Tozan]

I just had mine rebuilt with a new TC the cost was around $4300.

 

[Plimbob]

I had mine rebuilt with Billet TC, Sonnax valves and the updated thermostat = $5,200.00.

 

[Just Fishing]

Parts all by itself when I did my own with a new pump (stator housing, bell housing, and pump) w/ a circle d 6l80 double disk converter ran me about 3k

that included some proactive replacements, all new bushings, clutches, 90% new steels, bearings, seals, sonnax upgrades like the heavy duty 6 gear piston, sonnax billet piston upgrade for the 1-2-3-4 + proactive replacement of that drum @ $250, I also sprung for the "Blue" heavy duty pistons.

before that I had already gone through the valve body, rebuilding the pressure switches, and upgrading everything with a transgo shiftkit + all of their extras.
Part of that kit I had upgrades for the transmission pump when I did the actual rebuild.

I thought it was an easy transmission compared to the first/last automatic I rebuilt, a 700r4/4l60.

Also, to note my transmission didn't fail, it was more of a proactive rebuild while it was easy to get to.
So, I didn't have much wrong with it.
It just needed the basics, updates, and upgrades that I saw fit to use.

I did have a broken wave plate in my 2-6 clutch pack, apparently that's somewhat common.
No signs that there might have been an issue before tear down.


I can see these getting expensive to rebuild once you add in labor for removal, install + the time it took to blue print the fk out of it.
Like getting the clutch pack clearances perfect, endplay within spec, testing, etc.
But man, what a pleasure to rebuild that transmission was.

 

[Swaggerwagon]

For a dealer-installed GM certified transmission you're looking at around $5-5.5K. My local indy transmission shop here that does really good work quoted me $3.5K for a rebuild on my 2007 including an upgraded billet TC. Fortunately I don't need it yet, but it's good to know the price anyway.

Would your 2007 have the six speed trans?

 

[Geotrash]

Would your 2007 have the six speed trans?

Yes, it does. The Denalis got the 6L80 in 2007.