Have a few questions since this is my first yota. Ive got a 01 prerunner with the auto tranny and 3.4 six, there are a couple of areas that the scheduled maint log wasnt clear on.

Diff Fluid- It appears they recommend every 15K, seemed a little frequent to me?

Timing chain- Just wondering what mileage is best for this item, I know for some other cars its 100k miles.

3.4- I have some friends with the 4bangers and they are great reliable engines, dont have any experience with the 3.4 liter, are there any areas to watch on these or are they as reliable?(has 47K miles)

Was considering an aftermarket muffler to add a little sound but not too much, anyone have any experience with a dynomax(usually quieter than a flowmaster) and have any idea what the exhaust diameter is on the 3.4, i cant find that in any muffler application guides on the net.

4spd ect auto tranny- any areas to watch or is this a pretty durable tranny.

The truck wont really be used to towing and probalby not too much off road stuff, and I'm pretty anal about keeping up my maintenance(usually use an excel spreadsheet) is any of this helps. Everyone tells me that a yota will last forever if properly maintained so Im trying to gather as much info as possible.

thanks