After replacing fluids in the t-case, trans, and both differentials, I started to get leaks on both sides of the front driveshaft. So I undertook replacing both seals that connect to the the t-case and front differential. Here I'm focusing on the front pinion seal (I posted about replacing the t-case seal here: https://www.yotatech.com/forums/f116.../#post52451101)

I thought I'd make this into a write-up of sorts for anyone interested. You'll need the following:

Impact wrench
14 mm socket
24 mm socket
3/8 or 1/2 extension (wobble type is helpful)
Seal puller
New pinion seal (Toyota part 90311-38047)
Chain (to keep flange from spinning. Alternatively you can put in 4H)
1/2 torque wrench
beam torque wrench (to get in-lb reading for pre-load)
1/4 to 1/2 adapter(s) for beam torque wrench
Three jaw puller (rent from auto parts store)
Socket or pipe or equivalent for driving in seal
Mallet
Screwdriver or chisel or punch (for unstaking nut, see what works best for you)
Punch (for re-staking nut)

Optional:
Grease and grease gun (it's not a bad idea to grease the driveshaft while you're down there)
New pinion nut (if you're replacing the old one)




*Taken after repair

First, drain the differential. Then, before you forget, make markings on the front driveshaft and flange so you can reconnect them in the same spot when you're done. This is to ensure they stay in balance. I did this with white-out; other people use chalk or spray paint. Just use whatever works for you.

Now remove the four bolts that connect the driveshaft to the flange as seen above (14mm). I was able to do this with a 1/2 in wobble socket extension and an electric impact wrench (which has a surprising amount of torque). I heated the bolts for good measure with a propane torch and was able to zip them right off. After getting them off, you gotta get the driveshaft detached from the flange. You can whack it with a mallet, or try hammering something to wedge between the two (without damaging it). I was able to use a screwdriver to wedge in between and break them apart. After that it's easy to set the driveshaft aside and let it rest on the sway bar.



Next, you gotta get the staked nut off. I was able to unstake it somewhat easily with some hits to a pointy screwdriver placed between the stake and the pinion. After that, I got some chain to keep the flange from spinning (see above). You can also do this by putting the vehicle in 4H, but I was uncertain what strain that puts on it, so I just did it this way. Once again, I heated up the nut and blasted it off (24 mm). Since I was replacing the seal, I didn't worry about the heat from the torch damaging the seal that was already in there.

Oh I should say, I took a picture of the nut before getting it off so I could have an idea of how tight to get it back on. Some people have mentioned counting the turns it takes to get the nut off, counting threads, etc. I just took a picture and blasted it off, but it's a good idea to be meticulous about this step. Basically, you want to get it back on to the same position it was before. This isn't too difficult with a nut that's already been staked, since you can observe as it gets tight how far you need to get it to where you can re-stake it. If you're using a new nut, you'd for sure need to count spins or do something else to get it to where it was.



After the pinion nut is off, you can get the flange off. You might be able to knock it off with some blows with a mallet. I just rented a three-jaw puller from Autozone. After getting the flange off, you will see the seal. I used a seal puller from Harbor Freight ($8) and it was easy to remove.


Toyota part 90311-38047

Next, get your new seal ready. You can buy after market seals from Autozone, O'Reilly's, etc. But getting the part from the dealer was actually a bit cheaper (about 10 bucks).
For me, this was where things got hard. Getting this seal in sucked. I totally messed up and ruined the first one. The second time around, I purchased dry ice to place the seal on for about 20 minutes before driving it in. This seemed to help, and was quicker than letting it sit in the freezer all day. Also, don't forget to apply grease to the seal lip. I also lightly sanded where the seal seats inside (in case there were any burrs) and then applied a bit of grease to help the seal go in.



This what I put together to drive the seal in. Originally, I tried using PVC pipe, but it wasn't nearly strong enough. I got the parts in the plumbing section at Home Depot, 2'' pipe fittings. The fitting at the end fits nearly perfect around the seal. The length enables you to whack it even with the sway bar being in the way. That said, the lack of room, especially if you don't have the vehicle lifted at all, is challenging but doable. Even with this makeshift tool, getting the seal in was a battle.



This was after driving the seal in. I'll go on record and admit it's probably not perfect. At the top, you can see some marks. I had to give it some hard hits to get it going in there because it didn't respect any soft hits. The damn thing would just shift to either side and eventually pop out. Eventually after a lot of cussing, I got it in. It may or may not look like it here but, after inspecting it, it looked to me like the integrity of the seal was intact, so I decided to go with it. Others may disagree with this choice, and we'll see if it holds up. But it's currently doing fine and not leaking. Now that I know how to do it, I can do another replacement if necessary. I imagine the after market seals from the auto parts stores are easier to drive in than the seals from the dealer because they appear to have rubberized coating on the outsides of them, but then again they may not last as long.

The seal needs to be driven in to a depth of 1.5 mm. The pipe fitting I made could make the seal flush, but its diameter was slightly bigger than the seal's, so I needed to find something else. I used , which worked very nicely. To check depth, I combined .70mm and .80mm feeler gauges that I could hold down in and get an idea. I also used a digital caliper from Harbor Freight which was only $20 and has a nice measuring device at the bottom of it for measuring mm depth. There is a lip inside that should keep the seal from being driven in further than 1.5 mm if you take your time and do it right.

After this, you put the pinion nut back on. I used the picture I took as a reference, and started threading it back on. On the last turn as the staked part of the nut was getting closer to staking area on the pinion, it really started to get tight. I used a torque wrench to get it there, just to have an idea of where the torque was at. The FSM says a minimum torque is 89 ft-lbs, at which point you check preload, and tighten as necessary. I set the torque wrench to 90 lb-fts, and it clicked just before I got the nut to where it was and re-staked it.

Initially, I thought I had an issue with preload, but I misunderstood. I was measuring the torque it took to spin the pinion nut, which was about 40 in-lbs. I thought this was way too high. But another user pointed out to me that the FSM says "Using a torque wrench, measure the preload of the backlash between the drive pinion and ring gear." This is a different measurement than what I was doing. Long story short, the pinion nut is in the position it was before and should be fine.

Hope this is helpful to someone else undertaking this repair. It was a bit more difficult than I anticipated, but with patience (especially with driving in the seal) is very doable. It's a job that a lift or jacking up your vehicle can make much easier, though I didn't do either.