What is the real power limit for a stock 5-speed Allison before 5th-gear limp occurs, and how many saved it using only a valve body kit?

[QuietDiesel]

The 5-speed Allison is legendary, but it has a clear breaking point when you start adding tuning. What is the true horsepower limit you've seen before 5th gear starts slipping into "limp mode"? Many claim that anything over 90-100HP over stock is a gamble, but how many of you have pushed further just by installing a valve body kit or a high-pressure spring?

Is a shift kit enough to save the clutches under heavy load, or is a full build the only way to play safe? I’d love to hear what your setup is and how much abuse your stock 5-speed has survived!

 

[TorqueCurve_Ace]

What is your current mileage? If your Allison already has 200k on it, throwing a valve body kit at it might actually do more harm than good by flushing old debris into the solenoids. I’ve seen guys save their 5th gear for years just by being smart with their right foot and keeping the tune under 80HP. How many of you have actually checked your C3/C4 clutch clearances lately? That’s the real indicator of how much life is left.