By popular request, my post on removing (and reinstalling) the 5th Gen Transfer case for the purpose of replacing the (leaking) input seal to the transfer case.
I had observed that there was a leak at the junction of the transfer case and transmission while lubing the drive shafts. The junction and transfer case were covered with caked on dirt and oil. As it is my wife's truck, I did this job while she was on a trip with friends in Texas.
I started with the typical how to videos on YouTube:
Toyota 4Runner Auto Transmission Replacement (Part 1 of 3) - YouTube
Tools needed:
Metric box wrenches, preferably long ones for breaking free the nuts/bolts on the drive shafts.
Metric 1/2" drive sockets, preferably 6 point.
1/2" drive torque wrench
Breaker bar or long screw driver to lock up the drive shafts while removing the nuts/bolts
Floor jack and stands
Start with draining the oil out of the transfer case.
First things you will remove are the driveshafts. On the rear drive shaft you will start at the transfer case output and remove the 4 nuts holding the shaft in place (the bolts are press fitted in from the transfer side, so the bolt heads do not move). Mark each side of the junction with a paint pen or scribe it so you can reinstall the balanced drive shaft in the exact same position. Then go to the rear and remove the nuts and bolts. It will help to jack the truck up from under the rear differential so the rear wheels/axle can rotate to position the nuts and bolts for removal. Lock the axle by putting in Park and applying parking brake, or use a long screwdriver to jam the spider joint in position. You can get a socket on the bolt head side and a box wrench on the nut side and remove the 4 nuts and bolts.
Now you will repeat the process on the front drive shaft. Start at the front differential removing the 4 nuts and bolts, using a long screwdriver to lock the spider joint against the frame. Then remove the nuts at the joint to the front of the transfer case to remove the 4 nuts. Slide the shaft forward to clear it from the transfer case bolts, then slide it towards the transfer case but off to the driver's sided to clear the front from the crossmember and you can then lower it. All of these nuts and bolts are torqued to 54 ft lbs, which is why long box wrenches would be preferable here.
Now you are into removing the transfer case itself. Start with removing the wire harness to the case. There are 3 plugs that you just press tabs on to pull them. There is a breather tube at the top of the passenger side of the transfer case that connect to the transmission that you need to pull from either the transfer case or the transmission connecting points. There's another breather tup at the top of the driver's side of the transfer case that just drops down the back of the transfer case that you can just leave. The wire harness is attached to the transfer case via bracket that is held by a bolt on the top of the driver's side that needs to be removed. In total there are 8 bolts holding the transfer case to the transmission. All but two remove from the rear. One at the bottom left removes from the front and has interference with the transmission mount to the crossmember that prevents full removal. You undo it as far as you can, then you will completely undo it as you split the transfer case away from the transmission. Helps to remove a small skid held on by 2 bolts here under the transfer case to proved better access to bottom bolts. There is a bolt on the top driver's side that also removes towards the front. It is best removed by daisy chaining extensions totaling about 2' to gain clearance for your wratchet socket wrench near the front differential. You can get a couple clicks of the wratchet there to get the bolt loosened, then get it full out spinnging the extension/socket by hand. These bolts are torgued to 17 ft lbs so none are are to break free. There is a bolt on the top passenger side that is a blind shot with socket and extension removing it to the rear. Then you're done and ready to pull the transfer case.
The transfer case weighs about 60 lbs, so most guys should be able to pull and lower it by hand. It will slide free of the transmission rather easily. As my input seal was leaking, it had about 1/2 quart of gear oil in the space between the transfer case and the transmission, which dumped out all over the place. Once you got the transfer case out, you've got a clean up job to do. I used the purple engine degreaser with scrub brushes, followed by hitting it with a pressure washer.
I ordered the seals and sealant from Lithia Toyota of Springfield online as their prices were $10.42 per seal, which is less than half the $24.05 my local Toyota dealer wanted. You will need the following:
90311-43007 Transmission Extension Housing Seal
90311-43008 Transfer Case Input Shaft Seal
00295-01281 F.I.P.G sealant (Permatex Black would work here)
Seal removal is easy. Pry the seal out of the transmission housing and tap the new one in using a large rubber mallet. Can also use an appropriate sized socket here such as 30mm or 32mm. Transfer cased seal is contained in an aluminum housing which is held to the transfer case wih 5 bolts. Remove the housing from case and slide off the input shaft, then pry out the seal and tap in the new one. Clean up the sealing surfaces of the housing and transfer case from the original sealant, then apply your F.I.P.G. RTV sealant to the housing side. Let it stand for 15 minutes, then slide it down over the input shaft and bolt in place. The bolt pattern will only let you install it one way. Let it cure per the instructions (I let it cure overnight). You are now ready to reinstall the transfer case.
Bench pressing 60 lbs is still doable even for a 61 year old old AF, but when you add in the positioning required, you need a second set of hands or a jack. With my 42 year old son at work and myself home alone, it was jack time. Get the jack in position under the truck, then lift the transfer case onto the jack and jack it up to where the input shaft is lining up with the transmission. Then you're pushing it into the transmission along with some shimmying to line it up. At some point in this process your aim is to get that lower left bolt (that stayed with the transmission housing and has interference from the transmission mount) started into the transfer case. Get it started, but don't use it to suck the transfer case fully onto the transmission. Instead get additional help by starting some of the other bolts on the sides of the transfer case so it is pulled into place in a straight shot. Bolts get torqued to 17 lbs.
Reconnect breather hose and harness bracket and plugs. Fill transfer case with gear oil (I used Mobil Delvac 75w90 Synthetic, F your Toyota 75w at $80 per quart as I have 336K miles on this vehicle using what I recommend).
Reverse the driveshaft removal torquing everything to 54 lbs.
It's about 2+ hours out and 2+ in, plus the clean up time. Seal install is just minutes and their cost is minimal. So really the cost is in the labor and you will save yourself a lot doing this, so don't fear it. There really is nothing to F up. In all total it's a total of about 24 bolts/bolts + nuts. Not technically difficult at all.
Update: my wife completed the two day drive back to our ranch in Montana and the 4Runner had no issues. Mileage should be at 337.5K miles now. I had tested it out in all gears driving it around in my yard (horse property in SoCal) and picking my wife up at the airport. Checked the next day and no leaks. I will check again when I am next up in Montana at the end of August after catching the Florida at Utah football game in SLC. In between I've got two weeks of work in sweltering NYC. Hope my nails are clean in time for all my meetings :-)
P.S. I did pull the strut support bars connecting between the crossmember and the frame, but this is unnecessary. While doing so, one bolt sheared off on the passenger side and the other was severely rusted and on the verge of shearing off, which is a cause for concern. I was able to get the broken bolt out with vice grips after hitting it with a MAPP torch for a couple minutes. New grade 8 flange bolts went back in.
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