If it is an automatic transmission every 30 thousand miles.
Now
it should. they are the same from 88-92
You should change your automatic transmission fluid in Toyota gearbox at least after every 30,000 miles.
You need to replace the speed sensor. It sends a signal to the speedometer and also sends a signal to the transmission on when it should shift.
when gm took over Toyota they did a lot of cars with the same engines. look at the engines in both, if they are the same engine then they should be nearly the same transmission
you do not need to change gaskets just a good flush will do the trick If the transmission pan has been removed, then you should replace the gasket. The only other reason for changing it is if it is leaking transmission oil from the gasket. Otherwise the above answer is good. Just watch out that whoever does it doesn't over tighten the plug. Toyota overtightened my wifes and trashed the threads. Had to replace the whole pan and Toyota wouldn't fess up to their mistake! There goes another couple hundred bucks!
The transmission fluid on a Toyota Sienna should be changed every 100,000 miles. This helps to prolong the life of the transmission and improve performance.
50,000 mi
Are you sure it has a cam belt. I think it has a cam chain. Look in your owner's manual or call your local Toyota dealer.
R134
It should be +38 to +41
The Toyota Dealer Service Writer Steve said Toyota Corp. does not suggest a specific interval. If the oil is black and/or burnt smelling, then change it. If you simply do a drain and refill, you will need 4-6 qts of Toyota T IV transmission fluid that costs $5.28/qt at Michaels Toyota in Fresno, CA. The fluid in the torque converter will not be drained (2-4 qts more). The dealer quoted $80 to do this work. If I do it myself, it will cost me no more than $30 for the fluid. You can refill the transmission fluid via the dip stick with a funnel.