November 03, 2022

How to Identify 8L90 Input Shafts

Did you know that there was a change to the input shaft of the GM 8L90? It’s not exactly clear when this occurred, but sometime during model year 2019, GM switched from 36 shaft splines to 41. It’s confirmed that all transmissions with RPO code MQE have the larger, 41-spline shaft. The 36-spline version has splines that extend all the way to the tip of the shaft. The 41-spline version has a smooth tip at the of the shaft.

Another quick way to verify which shaft you have is to take a caliper measurement of the spline O.D. The caliper will show approximately 1.081" for the 36-spline version and 1.235" for the 41-spline (Figures 1 & 2).

Figure 1 – 8L90 Shafts
GM 8L90 Shafts
Figure 2 – Measure Splines with Caliper
GM 8L90 Measure Splines with Caliper

Related Units

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