4L60E Slips in 2nd, and has no 4th

[Beltbuckle Bill]

Hi everyone, I have a 2010 Sierra 4.8L 2wd 4L60E that is having problems. Details as follows

 

-189,000 km - I bought the truck with a freshly rebuilt transmission with paperwork to prove it. Work was done by local tranny shop

 

-190,000 km - lost 2nd gear completely, taken to repair shop to be repaired under warranty. Once repaired truck had a very harsh 1-2 shift for a while but slowly mellowed out to what I'd call normal. Drove fine like this until now

 

-195,000 km - lost 4th gear completely, 2nd gear slipping under heavy throttle. Slips even more when put in manual 2nd gear

 

I drive like a grandpa and don't beat on the truck at all. I don't have a scan tool to check if it's commanding 4th shift but I'm guessing that's not the problem anyway. Based on some research I'm leaning towards a cracked servo piston/bad seal but need someone knowledgeable to chime in. Also curious how the harsh 1-2 shift factors in to all this. Thanks!

 

Tom