4L65E shutter

[dna9656]

Got a 4L60E upgraded to a 4L65 E in my 06 Z71 LT 1500 Avalanche. I had converter shutter at 40 mph, the rebuilder put friction modifier in the trans and the over 40 mph shutter left, now I got 20 to 30 mph shutter. After reading the TSBs on the transmission I think the converter needs to be replaced. Your opinion(s) on this would be much appreciated. I'm going to see the man tomorrow the 18th of Dec. TIA