This is a non-trivial task because the beast is heavy. You don’t have to disconnect the diff from drive shaft or half shafts, you just gotta unfasten the 3 big bolts and 4 little bolts that hold the subframe in place. But you do need to put together something to support the subframe, because with the diff fastened to it, the subframe is really heavy. The objective should be to “drop it a little bit” on to something you’ve put together to hold the weight.
Solutions vary, but when I do this I have to knock the 2 subframe bolts back up into the passenger cabin. Those bolts are anchored into the body with some vertical serrations. The bolts won’t spin unless the mating steel on the body is damaged, but the bolts will allow themselves to be banged up.
Once the bolts are banged up, the subframe will have freedom to move. If you choose to bang those bolts up, you have to take care to protect their threads. So leave the nut on the bolts and put it a little “proud” of the bolt itself. That way you’re banging on the nut, not the bolt.
Once the nut on the end of the bolt is preventing you from knocking up the bolt any further, use another bolt, prob 14mm, as a “drift” to bang the bolt up all the way.
If you do decide to drop the subframe, then this is a good time to replace subframe bushings. These can be a little hard to remove, but personally, they’ve not given me trouble. There are subframe bushing removal tools, or you can homebrew something. Folks often burn out the subframe bushings, but that’s not really an option if the drivetrain is still connected.
This is also a good time to cut a bit out out of your subframe bushings. Take a vertical slice of the subframe bushing right next to the rtab bushing fastener. That will give you more clearance to get a wrench on to the rtab bushing fastener…greatly reducing that headache. Just don’t take so much out of the subframe bushing that you compromise it.
Another charm of banging up the subframe bolts, is that it makes it pretty easy to put the subframe back in place. With the drivetrain still attached, the subframe is very hard to move around. So getting it to mate up with those bolts can be really hard. But with no bolts there, it’s much easier to make the small adjustments necessary to get the subframe back into place. Then you can shove a rod up into the passenger cabin to locate one side, and then pop in the bolt (from the passenger cabin) on the other.
Once you have a bolt popped into place, use something to give it a bonk so it goes all the way down. That will allow those serrations to bite. Don’t over-torque the nut on the bolt, you might strip those serrations.
Scheme carefully re. how you’re going to support and move around the subframe while you reinstall it. If your “support and move around” plan doesn’t work that well, you’re going to have to remove the diff from the subframe. That will make the subframe light enough that you can then easily put it back on. Of course, now you have to re-connect the drivetrain bits.
Be advised that you have to put the drive shaft into the subframe’s hole before you fasten the subframe in place. Once the subframe is in place, the driveshaft won’t want to go into the hole. Some folks will tell you different, but I tried and tried and was not able to pull this off. So I would get the subframe “kind of in place”, poke the driveshaft into it’s hole, then finish putting the subframe in place.