2001 Isuzu rodeo 4wd put transmission fluid but only goes in reverse not forward it's there a button or something that I have to push to get it to go forward.

SOURCE: when i put my car in reverse it won't move but will drive forward perfect and is full of transmission fluid

Assuming this is an automatic transmission, odds are you have lost a band in your transmission, this will require a rebuild,  you may also notice it will fail to shift into high gear as well?

SOURCE: How to check transmission fluid

Easier done on a lift, but you need to start the vehicle and let it warm up and then remove the fill plug not yhr drain plug, (with the vehicle running) the plug will be found on the transmission pan but it is NOT the one on the very bottom of the pan, there is another plug up in the corner of the pan on the passenger side. Remove this plug carefully, for the fluid will be warm to hot, if a little runs out of the hole your ok, if nothing comes out with the plug completely removed you need to add a little at a time thru this hole until it runs back out. DO NOT SHUT THE ENGINE OFF WITH THIS PLUG OUT, fluid will run out if you do.

To get fluid in the hole, attach a small hose to a filler top off of a gear oil bottle and put that top on your tranny fluid bottle, turn it upside and squeeze the fluid in using the hose to get it into the pan. If you have a fluid pump it would be better but if not this will work.

SOURCE: how to fill transmission fluid 1999 isuzu rodeo ls

Lee2fixit doesn't know what he talks about on 99 Rodeos.

There is no dipstick tube - there are two access holes on the side of the transmission. The bottom one is to drain it out. The top one is to fill it back up. It is full when the fluid comes up to the bottom of the top hole.

Or you can take it to a dealer or service center to have it done.

SOURCE: 2001 Isuzu Rodeo transmission

under the truck you will see the large trans fluid pan. there are two 3/4 inch bolts. one recessed about 2 inches and one flush with the bottom of the pan.  The recessed one is the fill tube and the non recessed one is the drain.  You will need a pump of some sort to pump the fluid in the fill tube until it starts draining out.  I think if you start the truck the fluid will lower and you can put more fluid in until it drains again.  I dont know yet what kind of fluid to use.

SOURCE: transmission fluid level

I have a 1998 Isuzu Rodeo however when I purchased the vehicle I managed to obtain a service manual on mine.
Mine is a V-6 3.2liter engine with automatic transmission and it took me a while to find out where I added transmission fluid at too.

It is located under the vehicle on the Passenger side of the vehicle and it is located on the transmission just before the transfer case. There is like a eye beam across one side to another then there is like a Indent the lower one is for drain and the upper one with a larger bolt like plug is the fill hole. I used a turkey baster with a large bulb like affair to **** the transmission fluid in to it from the bottle then I inserted the baster up and into the hole vacated by the plug. Then squeezed the fluid into the transmission and kept at it till the fluid dripped out on its own. I hurried and inserted the plug into the hole and screwed into it and tightened it up and lowered the vehicle down checked after the vehicle had been warmed up and re jacked the vehicle up and rechecked and all I needed was a small squirt into it and it was full and since then it has been running really well since.

Lucky W Donegan [email protected]
Polson, MT.