Drive shaft pushes forward on the output shaft due to spline lock.
Replace the OEM retaining ring with this new split ring retainer.
Sonnax offers split ring retainer 100420-01K as an upgrade to the OE open-end style retainer that commonly breaks.
The OE snap ring directly behind the rear output shaft bearing often fails from fatigue cracks caused by the on/off loading of the snap ring. The open-end-style snap rings cannot withstand the loads from the forward force of the driveshaft.
The driveshaft spline is designed to slide on the output shaft spline, but spline lock causes the drive shaft to directly load the OE snap ring. When the rear suspension moves up and down, the drive shaft pounds this snap ring until it breaks.
Contact a Sonnax Parts Distributor.