Without no doubt, this is the Fred Wesley swing. Unfortunately, I don't have too much to add to this entry. The music speaks for itself. This is a great example of playing "in the pocket," where the rhythm section sets up a groove so tight that you can play anything on top of the groove and it'll be funky.
Fred Wesley makes it funky by using syncopated rhythms, by accenting the off beats. He usually does this by hitting every other note in a triplet, creating a 2 eighth-notes against 3 eighth-notes effect, or hemiloa. This can be a tricky rhythm because you can fit more 2-note beats in a bar of 12/8 than you can in 4/4 meter, yet Wesley is still able to easily land back on the downbeat because he's always "in the pocket."
Harmonically, this solo strictly uses the F blues scale. Fred likes to hit the high C for power, and messes with the b5 and 4 of the scale, B and Bb respectively, to create the bluesy sound. During his second solo, Wesley works his way up to a high Eb. He's able to produce a solid tone by keeping a strong stream of air constant in his playing, as opposed to "squeezing out" the high notes. When you break down Fred Wesley's style, his tone comes from the powerful air support behind his playing.
SPECIAL THANKS to pirahnahead Detroit for the comments!
There are a few videos out there of Fred playing this tune with his current band. Again, he appears to be playing the recorded version of this solo in a live setting, which means that you must learn this solo as well. And it's interesting to actually see Fred play this legendary music. However, I'd like to focus on this other YouTube video [expired] from a classic episode of Soul Train. This is what happens when you are playing "in the pocket." People get down.
Recommended Reading: Hit Me, Fred: Recollections of a Sideman. Written by Fred Wesley Jr. Published by Duke University Press.