About to do a transmission filter change on my 1994 Ranger 4.0 automatic, is it a bad idea to vacuum transmission fluid out the dip stick filler tube with a plastic hose to remove more old fluid, or will this cause problems? Would like to get most of old fluid out of system as it is almost black and smells bad, can someone help me on this?
It won't hurt anything and will reduce the mess potential. Keep in mind that there will still be some fluid left in the pan. So, take care when dropping the pan.
I would also recommend doing at least a fluid change twice, maybe three times in order to get the majority of the old, burnt fluid out of the transmission. Do some driving, going through all the gears, in between the drain and fills and change the filter after you drain the fluid for the last time. Most of the transmissions I know of hold around twice the amount of fluid that normally gets drained when you drop the pan (most of the remaining being in the torque converter). Since there will be some fluid mixing during the drain, fill, and drive cycles, doing it three times will get the majority of the old fluid out of the system.
Check to see how much fluid the transmission holds so you have enough on hand. There are two amounts. The dropping the pan to change the fluid and filter amount and the total capacity if completely drained after doing work on the transmission amount.