Cummins 605/2050 immediate RPM drop issue

[tree98]

I don't know how familiar you are with new emissions engines but they drop rpm very fast because of back pressure that the old engines didn't have. I have a 9 liter cummins that you have to rev out the max and shift quickly or you'll miss the gear because it's dropping rpm so quickly. Not saying this is your problem just throwing it out there.