Transmission slipping between 2nd and third

Question by John DeMitis posted 6 months 2 weeks ago in M-Class

I have 2006 ml500 with 722.9 trans. vehicle only has 55k on it. Been running great. The other day it started to slip between 2nd and 3rd. Every thing else works great. Did a trans service with new fluid and filter but still have same problem. Any suggestions?