What would happen if you ignored and don t fix the pinion bearing on your differential?

Have you made a deal with your old differential to not lock up or leave you stranded someplace and have a tow truck ready to pick you up...I had a driver bring a car from the dealer , 5 miles, he didn't have time to leave it for warranty...it just started making noise, he said...I backed it out of the parking space put it in drive...that was it! The pinion walked back into carrier it stopped right there...called Dodge to tow it in....so when my daughters diff on her Dakota started making noise, It went in the shop for new bearings and seals...some thrust washers and labor... done in one afternoon 150 dollars less then the cheapest used diff I could find...

It shouldn't hurt the transmission, but that's up to the driver maintaining control and staying on the road with the rear tires locked...I'm told the Rovers flat spot both rear tires when they skid to a stop....

If that is all that is wrong it should be less to get it fixed than buying a used one. Has anyone ever bothered to check the lube int he axle?