Why do we have rev limiters and speed limiters?

blkthndr

former sccoa webmaster
All 4R70W SC’s have rev limiters because the 12 inch torque converter starts
to balloon around 5400 rpm. If it balloons enough, the trust washer could eject.
Therefore, the rev limiter keeps drivetrain speeds down.

The speed limiters are present in the 4R70W SC’s because the driveshaft starts
to bend near its critical speed which can depend on rear gear ratios and tire
sizes. The critical speed is when the driveshaft starts whipping in the middle
rather than spinning on its true centerline. This bending creates a vibration or
frequency. The frequency can cause the tailshaft housing to fail. The rear
bushing also gets much hotter and can spin thus dropping the driveshaft at high
speeds. The M5R2 equipped SC’s and XR7’s don’t have this problem because
the driveshaft is shorter and the tailshaft housing doesn’t see as much
frequency. --- compliments of A-Train
 
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