I am planning on doing an initial drain and refill at 15k then will be doing one every 50k. This is based on what the fluid looks like at just 50k miles as noted in the example below:
Transmission Fluid Change Results - Toyota FJ Cruiser Forum
My plan is to keep the truck for as long as I can. I understand the regular recommended service is 60k for towing/off road use and 100k for regular use but I don't feel comfortable with that. Call me old school, but to me doing it at 15k then every 50k helps me sleep at night.
I also believe in changing at low mileage, but about 25k. Biggest problem has always been people and shops overfilling, so many cars do not have dipsticks/easy access to filling. Eleven qts. of oil expands quite a bit when heated. Under-fill becomes apparent because trany doesn't shift right - although correct level important, an ounce or two when talking 11 qts is not. Get to about correct temp, open level plug - a trickle is solid and a drip is interrupted.
- a trickle is solid and a drip is interrupted.