Transmission slipping but no CEL or DTC codes on 2004 Chevrolet Suburban 1500

No indicator lights at all. Trans slipping from 1st gear on. Fluid level good, changed fluid and filter, still happening. Using a Matco MD9040 reader I get no DTCs. HELP!

sounds like a bad transmission. the friction plates may have lost their friction material. how many km
117k on the truck. I thought that would be the problem but I was hoping there may have been a cheaper solution. Thanks for the response gearhead
another possibility is sticky valves. try some lucas brand transmission fix. sometimes this will help. maybe even fix it if the friction plates are okay
Unfortunately you were right. Took it to an Aamco shop and 3rd and 4th gear are shot, most likely the friction plates. I'm disappointed with this Trans. I always did the services and didn't beat it at all. 2k for a rebuild. Thanks for the input gearhead. I appreciate it.