sorry about the delay 
Transmission filter replacement, 1999 Isuzu Trooper, 4L30E automatic transmission.
Prep:
No joke, this is the
messiest project you will ever do to your Trooper, period. Get a box of rubber gloves, a container large enough to hold 5-8 qts of fluid, and maybe a cheap plastic drop cloth for your workspace. I had an old shower curtain I tossed out after doing this. A bag of cheap cat litter is helpful as well. Wear old clothes, you will be pretty much bathing in ATF.
Tools: 1/4 and 1/2 drive socket wrenches, 10, 12, 17, 18mm sockets, a 4" 1/2 drive extension, a cheater/breaker bar, hammer and soft chisel (in case the pan sticks).
Consumables:
Two cans brake cleaner, RTV sealant, automotive weatherstripping adhesive (optional, but helpful), 1 case of Dextron III automatic trans fluid, 1 filter kit (filter and pan gasket), PB blaster or other penetrating lube, six-pack of Sierra Nevada ESB (or non alcoholic equiv.)
NOTE:
I'm going off of memory here, so the bolt sizes I have listed are quite possibly wrong.
Steps:
If you have even a modest lift (I have 3" in the rear) You should be able to perform this task without jacking your truck up. If not, jack the front and place it on jackstands. Chock the rear wheels.
There's a suprising number of wires and sensors
inside the pan. Disconnect the negative battery terminal to be safe. I did not know about the wires, so I did not do this step and it came out ok; however, I would err on the side of caution if I did this task again.
Read the rest of these instructions and identify the bolts for the skid plate and crossmember. Hit these with a healthy spray of penetrating lube so they can soak while you drain the transmission.
Drain the transmission into a sutable container. You can continue the next steps while it drains.
Remove the transfer case skid plate if you have one (4 17mm bolts)
(***optional: You have unrestricted access to the drain and fill holes to the transfer case now, may as well check/replace the fluid since you're already going to be bathing in ATF.***)
remove the transfer case mount nuts from the crossmember. They are located inside recessed holes just under the transfer case about 4" apart (2 18mm? nuts). My holes were clogged with mud making them dificult to find.
Loosen (->DO NOT REMOVE THEM YET<-) the eight bolts that hold the crossmember to the frame (4 each side, 17mm)
Place a small jack under the transfer case to support it. Once you remove the crossmember, the transfer case will fall unless supported.
Remove six of the crossmember bolts (3 per side) leaving one on each side.
loosen the last bolt on the passender side of the crossmember to about 1" out. you want the crossmember to swing down once the other side is unbolted, but not come completely free. Theres a small wiring clip on this side and this will allow you access to the back of the transmission pan bolts without having to remove that wiring clip.
Remove the drivers side bolt, carefully swinging the crossmember down and out of the way. If the wires on the passenger side look strained, maybe support the member with a brick or something. You finally have unrestricted access to the transmission pan.
(***optional: at this point, you have great access to your transmission range mode sensor. If you've never removed and cleaned your sensor, this is a great time to do it ***)
Using a short extension on your wrench to clear the pan, remove the two-dozen or so 10mm bolts from the pan by first breaking them free, working in a cross pattern (losen one on one side, then one on the opposite side, etc), then remove the bolts. Clean the bolts with brake cleaner and set aside.
My pan was pretty well stuck to the tranny and needed a little assistance with a hammer and soft chisel to seperate them. If you do this, work slowly and carefully so as not to damage the mating surfaces.
Throughly clean the remaining gasket material from the pan and the transmission. This actually took the longest time for me out of all of these steps. Make sure you get it all, If the gasket does not seal, you'll be doing this all over again.
Remove 4 12mm bolts holding the filter on. Pop the old filter off and check to make sure theres no old gasket remaining on the return hole under the filter
Scrub the pan, inside and out, especially the magnet finish with brake cleaner to eliminate any moisture. Spray off the bottom of the trans with brake cleaner as well, making sure you flush those bits of old gasket away and allow to dry.
put a thin bead of weatherstrip adheasive on the pan and line up your gasket on it. Don't use silicon gasket stuff as its slick and the gasket will slide when you try to install the pan. Make sure you put the magnet back in the pan.
Bolt the filter to the transmission firmly.. Don't overtighten, its plastic.
Bolt the pan to the transmission. I used a dab of RTV gasket sealant on the threads of each bolt to keep them from vibrating loose over time. As you tighten the bolts, remember to use a cross pattern again, starting with the corners, then moving back and forth so that the stress is distributed across the gasket surface evenly.
Reinstall the crossmember and transfer case mounting nuts. You will need to take your time and line up the studs on the mount with the holes on the member. Once its all bolted up tight, remove the xfer case jack.
Remove the upper fill plug on the trans pan and fill with as much dextron III as it will hold. I have a 1 gallon container with a plastic pump top and hose that I specificly bought for pumping transmission fluid up into this thing. It took just aunder a gallon for me to get to this point. However you choose to do it, make sure you fill the pan to the top before starting the truck.
Start the truck. While the truck is running, go back to filling the transmission, as the fluid will have started to work through the system, lowering the pan level. Again, fill until fluid dribbles out of the upper hole. Reinstall the fill plug.
Do not reinstall the skid plates yet. Lower the truck from jackstands if need be. Take the truck for a short drive, warming up the transmission.
LEAVE THE TRUCK RUNNING when you get back,
set the emergency brake and block the wheels. Crawl under and check the pan for leaks. If there are no leaks, remove the fill bolt again and pump more fluid in there. You simply can't overfill this trans as it will overflow out the hole. Make sure you get a nice dribble of fluid before you plug it up again.
Reinstall the fill plug, shut truck off. Reinstall skid plate. Check for leaks again. I took my truck to a carwash and hosed the fluid off of everything under the truck so I could see leaks better.
It took me about 5 hours, start to finish including installing a remote cooler up front.
