Seems like a lot of things are ridiculously low on the maint. schedule like the timing belt but there is no regular schedule on the tranny?
At least in my 05Lx maintenance schedule it calls for inspection of transmission fluid every 30k, and to replace fluid every 60k (yes that's technically qualified with "Required only if vehicle is operated primarily in desert, on dirt roads or while towing").
I wanted to simply add some Lucas to mine but there is no FING dipstick. The fill plug is in a really ****ty spot and there really is no way to get anything in there without a pump......unless I am missing something.
03 and up use the sealed transmission and WS ATF (World Standard). Sealed as in there's no dipstick. The 100 faqs explain more and you can find lots of info on it - it's by design and one explanation is that the fluid is very hygroscopic (absorbs water) and that's why it's sealed. Another more cynical explanation would be to discourage amateurs from maintaining their transmission fluid, or to minimize the likelihood of accidentally putting the wrong fluid (i.e. wiper fluid or engine oil, or whatever) in the tranny.
Here's a link from the faqs:
https://forum.ih8mud.com/100-series-cruisers/22580-type-t-iv-atf.html
Bottom line, you can add fluid, but the refill plug just isn't as accessible and yes you do need a fluid pump (walmart or any automotive store sells them) and yes that makes it all more of a pita for those with 03+ WS ATF Sealed Trannys.
There are a few writeups on tranny fluid level check and on full atf fluid replacement (flush can be a bad word to some). Some prefer to just do more frequent drain and refills rather than the full replacement.
I posted the flush procedure I used:
https://forum.ih8mud.com/100-series-cruisers/447398-ws-atf-flush-procedure.html
bkgee posted another approach (
https://forum.ih8mud.com/100-series-cruisers/356884-tranny-drain-fill-percent-new-fluid.html) the other approach of frequent drain/refills to accomplish the same thing - you can do it over a short period of time or over a long period of time (as in each oil change) so that in a similar timespan you've accomplished a full flush.