5th gear spline wear is becoming more of a problem lately to the point we thought we would share our findings. The pictures show wear on both the input shaft and gear. Unfortunately, the only way to repair this is to replace both the shaft and gear assembly. We inspect all gears and shafts for spline wear on all of our rebuilds. If we see wear, we will contact you on price and what needs to be done. The input shaft and gear we install have larger splines to prevent the failure from happeneing again. 

We think this might have something to do with harmonics on non-balance shafted, and stroked engines, and we seem to see this wear on modified engine EVOs only at this time. The spline wear is chatter wear from the gear and shaft moving forward and back at a high speed for a long period of time. Eventually it will wear the splines out completely to the point that 5th gear will no longer work, and the car will feel like it is in neutral.



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