The first half of my morning commute is on back roads averaging 30-45 mph. This whole time I drive in 3. For the second half I get on the highway and average 50-70 mph, depending on traffic. I guess I should mention that I took the alda out of the car.
What I have been doing is keeping it in 3 when I get on the highway until I get up to about 60 mph for about 30 seconds, then I shift into D. Sort of a mini Italian tuneup every morning.
The question is, is shifting from 3 to D at 60 mph every morning going to lead to tranny problems? Should I shift back to D while stopped before I get onto the highway?
Thanks!

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1983 MB 300SD Turbo Diesel