Constant velocity (CV) joints depend on two primary things for long life and happiness. First, special CV grease keeps them lubricated, and second, a CV boot keeps said grease in and contamination out.
The outer CV boots on my '04 Toyota 4Runner have been leaking for some time now.
When I installed my Total Chaos long-travel kit, part of the process was to fit the CV shafts with longer axles. This meant taking the CV joints apart, replacing the stock shafts with longer Total Chaos units, and re-assembling the whole shebang.
As a precaution, I purchased new inner and outer CV boots from my local Toyota dealer. The factory Toyota inner CV boots are a soft rubber that's actually quite durable. The outer boots, on the other hand, are a hard plastic that doesn't flex very well.
The inner CV boots have held up great, but the outers have leaked from day one. I thought that the stock Toyota CV clamp might have been the culprit, so I replaced the clamp with the T.C.-supplied hose clamp that came with the long-travel kit. The grease continued to leak.
I decided that the stock outer CV boots had to go. Some research online and at the parts counters of two local auto supply houses revealed that no one makes a direct replacement boot for the outer CV's on '03-and-newer 4x4 4Runners. This same CV boot is used on the '05+ Tacoma's and the '07+ FJ Cruisers. I was bummed, but remained too stubborn to give up.
A little more research uncovered a universal CV boot made by Dorman Products. Constructed from soft, compliant neoprene, the Dorman Uni-fit CV boot can actually be stretched over the outside of the CV joint using a special Dorman installation tool, allowing boot installation without needing to take apart the CV shaft. The CV boot part number is 614-003, and I was able to order a pair (they're sold individually) through J&C Auto Parts in Whittier, California.
I didn't opt for the CV boot stretching tool, so my installation was done in the traditional manner requiring removal and disassembly of the CV shaft.
When I opened up the passenger's side CV axle assembly, I discovered that the joint was almost out of grease and it wouldn't have been much longer before that expensive CV joint was toast.