Hot tip on setting up preload on a Nissan R180 LSD: don't do anything! I spent a lot of time setting them up for 105 ft-lbs of breakaway back in the day, which was the accepted hot tip according to all my inside sources at Datsun Comp (before they fired everybody but the secretary), Frank Leary's car builder, and Jason Jasensky hissownself. When we started having serious overheating problems (more on that next paragraph) I started backing off on the preload (common sense would tell you to increase the preload to eliminate some of the slipping, well we did that too and all it did was start dragging the tires around) and it didn't change lap times or handling. Eventually we were running the stock 45 ft-lbs of breakaway or whatever it is. The preload only really affects your off throttle condition: if you drive a Z in ITS the proper way- that is by using the go pedal as an on/off switch, then when the switch is on the rods rides up into the ramps and locks you up pretty much anyway. There is no partial throttle or coasting like there is in a 600 hp Trans Am car. I've said this here before, the driver's job in an ITS 240Z is to put his foot thru the firewall as soon as he turns in and the Crew Chief's job is to make the car handle so the driver can do that. That my friends is how you achieve ITS 240Z Nirvana.

Now then, 4.11's and overheating Z diffs. We found that any time we ran over a 3.7 ratio we couldn't keep them from overheating. Tried multiple gear sets, different LSD preloads, different gear contact patch setups, and every kind of synthetic and hypo gear lube you could buy. 15 laps at Road Atlanta and we'd be puking diff fluid out the vent, smoking bearings and all sorts of other nasty stuff. Doug Stewart was having the same problems at RA also. Dunno if John Williams was or not. A 3.90 was what the current config of RA needed (4.11 really but 7700 rpm was a little more than what we were willing to twist the crank to). Put a 325 degree tranny temp guage on the diff once and after about 12 laps the needle had gone all the way around back to the zero stop and broke off. Charlie Shatzen at Mazcare suggested a tube of BG Gear and eureka! No more puking diff fluid. Hot yes, but not smokin' hot. So BG is your other hot tip. I think we used it with Redline or Torco, can't remember the final recipe.