My truck came with a standard "open" rear differential. Considering my hook up problems at the track I decided to install a Detroit TrueTrac limited slip unit. I must say that the TrueTrac worked perfectly for 25K miles then it started to clunk and chatter when I took a turn. This condition only happened after a good posi-burnout and it seemed to go away after a few good turns.
I was going to change out the oil in hopes that it would cure the problem but when the oil was drained, small pieces of metal came out too! I replaced the unit with the stock differential for now.
I disassembled the unit to figure out where the metal came from, I could not find any obvious problems other than the side gear pinions being stuck in place. I discussed the matter with a tech. from Randy's R&P, he told me that running tall tires could cause the pinion gears to scuff the side of the case. I think this is the problem that I experienced even though I am not running tall tires. I think my problem relates to the "clutch from hell" (ACT 6Puck) and other engine modes combined with my style of driving (burn-outs, very hard shifts etc)
Source: http://www.4crawler.com/4x4/TrueTrac.shtml#TrueTrac
The TrueTrac still worked when I took it out and I believe it would be OK for easy use for many more miles but for now, I am going to stick with the stock unit. I may install a Detroit Locker if I get sick of the open diffie and have an extra $500.00 laying around.