Hi Larry,
Thanks for the input, I totally agree on the tranny and Differential lube schedule (change at 100K miles) that you mentioned if you're using the 70-90or 90-140 weight lube. I do disagree when the tranny is lubed with automatic transmission fluid (in my case the 190D with Dextron).

I also have a '97 Ford pickup with 5-spd manual that is lubed with Dextron.
I also change the tranny fluid in it at 25K mile intervals. The Ford has 196K miles and the 190D has 572K miles. At the 25K mile change intervals the Dextron that comes out is very dark, almost black. My guess is that the frequent fluid changes keep crud from accumulating in the gearbox.

Let's see who can get to 600K miles first, I've got only 28K to go. Again, thanks for the input, I respect your opinions very much
Al