I believe it is a Cat engine brake???
How much does it cost to have one installed? I had one on a 3406B and loved it.
Today I went down a 6% grade and it would only hold at 20 mph while everyone else was blowing my doors off.
I have a Cat 3406e (Serial# 5EK61336) that has a weak engine brake. I just had an overhead done, installed 3 new solenoids, installed new wiring...