VN Automatic 1st 2nd ok 3rd problem

[madmatt2006]

Hi All I'm new here nice looking forum I have a problem with my auto I just chaged the oil and filter because the oil was burnt and smelt bad. After changing the oil and filter it shifts perfectly in 1st and 2nd but when it hits 3rd it is as if the cars is in nutral and the engine hits the rev limiter. The car was fine a few days before the oil change drove over 500Kms no problems. Any ideas of what's wrong? I watched a rebuild video from GM could it be somthing sticking or a band or somthing else. Is there an additive that may help?

[Shifty1]

Sounds like your clutches are slipping... when you opened the transmission.. was there metal filings in there?