I've done business with a place in Santa Clara called Rear end Specialties a few years ago on my old ranger prerunner and my mustang. he did a great job on both and was able to get them done in 1 day each. I never had any noise or any problems from his work.
I've also worked with a place called Pete's gearshop in Hayward. he also does great work but is usually more expensive than people around him.
I would stay away from Jaws Gear in Sacramento (not exactly in the bay area though.) The reason I went to rear end specialties was because Jaws toasted the rear end in the mustang. I installed 4.30s with a brand new differential. it made noise from day 1. they insisted it was just break in noise. then after the break in period, they claimed that its common for 4.30s to make noise. the more i drove it, the worse the noise got eventually the axle seals leaked and they told me I could take it back up to them (i live in Pacifica) and they would change them for me at an hourly rate. They weren't warrantying their work whatsoever. It got so bad that I eventually took the cover off to inspect and found my ring gear was hanging on the differential with 3 loose bolts left. the rest of the bolts were just floating around in the rear end totally stripped causing me to have to replace the whole differential due to damage.
