I have a LS4 with the Auto FWD trans essentially the same one as all the V6 GP's except that it has a looser converter.

We were at the dyno, and at around 4700rpm it does some weird thing almost like the line stops ans starts again lower (Dyno operator mentioned he sees that usually when converter's are not holding the power), then it's good but at 5500rpm it just takes a complete dump. Between 5500 and 6000rpm I lose close to 175whp while the car is still WOT. The scans look good as far as air/fuel/spark and everything so we don't believe it's engine related.

I would like to note that it also does this on the street, you can for sure feel that it's got no more power after 5500rpm.

Has this happened to people before? If this is semi-common then we'll change the converter but if this sounds like a retarded theory we'll look elsewhere for problems.

 

Post the dyno graph, also were you attempting to lock it for the dyno run? If it was unlocked, the converter would slip and never recover, your rpms would climb while the torque and power dropped off. If the converter was locked for the run, it could possibly mean the converter clutch is having a problem holding or your are loosing pressure to the TCC. What kind of converter and what mods do you have? We need mreo info to help diagnose this.

 

The Converter was unlocked, what is the purpose of locking the converter when on the dyno? I thought the converter only locked up when in low load or at cruise, it doesn't lock up on the street at WOT....... I don't need to lock it to get good numbers...and I don't want to totally fack up the converter either.

Any other thoughts?