Rear shocks on Jeep Cherokees (Real cherokee, the XJ, not some pansy grand cherokee or liberty) are secured on the top by a flattened bar with notches for the mounting bolts, which isn't very strong. A BPE is much stronger. An extra inch of shock length is also gained by moving the shock end further from the body, which can allow for a bit of lift (hint hint for the budget boost people) without the shocks being damaged by overextending.
What we are doing here is using rear sway bar brackets as BPEs, since they are plentiful and cheap, and many people have them already left over from removing their REAR swaybar. (Removing the front sway bar is VERY dangerous, and is generally discouraged in all modding communities. Only disconnect it on the trails if you need the extra flex, and reconnect it when on the road. There are plenty of stories of those who have died from removing it, and none from people who are glad it's gone on road.)
This instructable was inspired by RockLizard's Budget Boost
And is very similar to lunghd's howto
I sure didn't make this up, and I don't know who did, but I try to give credit where it is due.
Step 1: Remove Rear Shocks
Presoak all the bolts in penetrating oil. PB Blaster works well.
There is one lower bolt for each shock which can be accessed from the rear of the axle on the driver side, and the front on the passenger side, and two upper bolts on each side that will require the use of about 8 inches of socket extensions (a 1/2" socket will fit nicely because of the layer of rust, but I believe they are actually 13mm).
You will have to use a breaker bar to get the bolts loosened (and impact wrench may be a bad idea, as it could break the welds holding the upper nuts in place. If that happens, don't panic, just google broken upper shock mounts and you should be able to find some solutions)
If your shocks look and feel good (they should re-expand when compressed), and you are under 3 inches of lift, you may be able to reuse them with the stock barpin pressed out. If they look like mine, or you are running more lift, you will want new ones. I'm now using rear shocks from a jeep commanche, which are 3 inches longer than stock for my 2.5" lift. Commanche shocks also do not come with a barpin, so one less thing goes to waste.
Step 2: Put the BPE Together
Unbolt the swaybar link from the swaybar bracket. Chuck the link wherever you prefer to have useless crap pile up.
Insert upper shock loop into the swaybar braket (now BPE)
With a washer on each side, bolt the shock into the BPE
Step 3: Mount the Shocks
Hold the BPE up to the original upper shock mount holes and insert both of the original bolts. Alternate tightening them, and try to keep them centered on the BPE.
Bolt the lower shock end to the lower shock mount.
Done. Put the wheels back on (if you took them off), bounce the jeep up and down a few times, and make sure it all looks good. Enjoy your extra shock length and strength.