3rd gear issues on a 2008 1500 6.0

[white1500]

An uncle just made it into Law Vegas and his 2008 gmc 1500 with the 6.0 is now having issues with 3rd gear.

 

1st and 2nd are fine but as it upshifts to 3rd it just revs and doesn't accelerate.

 

I think that there's a TSB out for a similar issue, does anyone have any ideas? Solenoid? Cracked clutch housing?

 

Tyia

[white1500]

My uncle managed to find a shop in town that's charging $1800 total for a remanufactured tranny. It'll be ready by Monday, so not too bad.