Jeff Robbins

Hi Does anyone know why the N/S output shaft oil seal leaks, apparently if it does the diff is getting shot. And can a shot diff damage the drive shaft end. The reason I ask this is that I have a 2004 2.7 Diesel on it's third diff. The latest one being a second hand unit from Eurojags with dry oil seals when it was put in, but after a few days the oil seal was leaking. The N/S drive shaft that goes into the diff had to be cleaned up (the bit that the oil seal mates to) with fine emery paper and I was told that if the seal start's leaking I would need a new shaft or CV end. Any thought's would be appreciated. Jeff