I have a 1994 E320 and twice in the last couple of weeks it will not shift from 3rd to 4th when hot. Both occations I was about 30 miles away from home and got back on the e-way and after a couple of miles it would slip out of 4th and be in a nuetral state. I would pull over, check fluid and start again and it would go from 3rd to 4th. So I crawled home at 35 mph. Had the transmisision looked at and service and he comented on how clean it was. It has about 165,000 miles and I have had it for the last 10,000. Any ideas???