drain/refill frequency on a seldom driven truck

[Ramblin Fever]

Truck does get drove over 100 miles every time it's started, but typically only gets drove 2-3 times a month.

In the past, when this truck was a dd, I changed the ATF every year with roughly 15k miles or so at each interval; fluid is VERY clean currently - but I haven't changed it in 4yrs.

Should I do a drain/refill?

Does one have to be concerned with moisture collection in the ATF?

Everything else was just recently done on this truck, truck shifts super smooth, but we are getting ready for a 2wk trip in 2 wks, this truck will be pulling a very light trailer up and over a few extreme mountain passes.

It's used to the mountains, so I'm not concerned with that, but I am concerned with whether or not I should do a refill - this is a closed unit, has to be refilled from underneith, not exactly an easy one.

 

[Rat407]

What is the make and model of the truck? It sound like it is in great shape and I wouldn't worry about changing it out.

 

[rfeir]

Leave it alone. Unlike motor oil, the combustion process does not add contaminants and water to the ATF.

 

[Ramblin Fever]

Truck is an Isuzu rodeo with the GM 4L30, currently has 205k miles. Original transmission, but I'm also the original owner

 

[LeakySeals]

I think its less of a concern than engine oil. Partly the composition of transmission fluid. But more importantly the environment the fluid resides in. A transmission is sealed up pretty tight, no dirt, fuel, very little air in there.