re: O-T Mechanic Baws

I have a 98 Frontier. Changed the transmission fluid and filter religiously about every 50,000 miles. At 150,000 miles it went out with no signs of slipping or hard shifting. Just stopped shifting out of first.

Had a used transmission put in that had 60,000 miles. I haven't changed the fluid or filter ever since and the truck now has about 305,000 miles. The transmission has about 210,000 miles. No issues. I have even done some heavy towing that was probably above the truck's capacity

There's something to the old fluid is best if it isn't burned. I gave up on doing the maintenance by the book. My 2 cents