My 1999, 250,000-mile 4x4 5.2 V8 Durango started acting funny when turning left at higher speeds about three weeks ago. Essentially, when I turn left at any speed above 10 miles, it feels like the transmission doesn't engage immediately or that I loose traction on the left side for a split second. This doesn't happen when I am turning right. The repair shop replaced the differential with a newer one but it didn't work, so they put the old differential back in.

Any ideas what could be causing this and what to look for? Thanks.