LSDs - $$$$

[Ron Earp]

Sort of funny. I mean, how much longer can a four speed drum braked car be competitive in ITS? Why are we racing it anyhow? It is almost 2010 and this thing was penned 40 years ago, as was I.

[pballance]

Sort of funny. I mean, how much longer can a four speed drum braked car be competitive in ITS? Why are we racing it anyhow? It is almost 2010 and this thing was penned 40 years ago, as was I.

Kids, can't take them anywhere!

[spawpoet]

Sort of funny. I mean, how much longer can a four speed drum braked car be competitive in ITS? Why are we racing it anyhow? It is almost 2010 and this thing was penned 40 years ago, as was I.

I don't see the problem Ron. Shifting and brakes just slow you down....

[MIKEL]

Sorry I thought the 240 could not run the late 5 speeds (oh yeah your not in a 240 duh! my bad )But seriously have you looked into that? The truck rear diffs are plentful and cheap. I heard that the OD box set likes the taller gearing and they are also a lot easier/cheaper to get. Sam N said somthing to me about that last year as an alternative to trying to fix/replace the comp boxes (and trick parts are available if you want to tweak/rebuild one).
I think this is what Don Ahrens did with his car (not IT but very close in the drive train)

[spawpoet]

Sorry I thought the 240 could not run the late 5 speeds (oh yeah your not in a 240 duh! my bad )But seriously have you looked into that? The truck rear diffs are plentful and cheap. I heard that the OD box set likes the taller gearing and they are also a lot easier/cheaper to get. Sam N said somthing to me about that last year as an alternative to trying to fix/replace the comp boxes (and trick parts are available if you want to tweak/rebuild one).
I think this is what Don Ahrens did with his car (not IT but very close in the drive train)

Just an FYI. On the truck diffs, if you get it from a salvage yards you'll want to get the front diff from a 4x4. The rears are solid axle. Depending on the year/model of the truck the r-180's are available in 3.9, 4.11, and 4.38.

[MIKEL]

Id num for trucks is on panel in eng compartment.
ca41 r180 4.11, ca43 4.375 ca46 4.625 look for 720s 80-83
86+ hardbodies and 720s (4.11 or 4.625) also some of the frontiers had ca45 (4.54) 2003+ , started changing to r200s mid 80s so look for 4 bagers, and yes will be on 4x4 front diff only. The 4.44 can be found on some of the subies (dont know which)
I got this off the nissan-infiniti forum dont remember where old post.

[spawpoet]

Ron, I did stumble across this price on an LSD unit, but I'm not sure whether it will be correct for your ring gear diameter.

http://www.nismoparts.com/catalog/?section=530

[MMiskoe]

I know you started off by saying you don't like gear types, but any way, look at OBX differentials. I don't know if they make something for the R180, but I did meet a guy who described having one in his 240, but not being a racecar it might have been an R200.

The 1987 1/2 to 1989 300zx turbos had a clutch LSD w/ a 3:74. 88 and 89 non turbo's got a 3:90 open. Both in the R200. The 3:74 clutch types tend to bring about $500 on the used market from what I've seen (and paid).

What is your aversion to the gear types?

[Tom Donnelly]

So Keith, what's the hot tip? And from what I remember Chet said he ran a 4:11 and it was hell on the valve train.

[kthomas]

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.

[MIKEL]

From what I have heard the OBX system dont hold up well to racing, mostly for street use. The Japs use the KAAZ and CUSICO? for serious drifting both I think are clutch type (not cheap!). The only other gear system that is used for hard core racing is the TORSENs on the MAZDAS and SUBARUs. I am not sure if the problem with disengaging with 1 wheel lift is present in the TORSEN but to my knowledge no one has swapped out the Subies R180s to the nissans (27 splines vs 30 for subies) on the imput shafts. I wish someone would fab up a inexpensive fix for this, the subies are cheaper and easier to get. If anyone does let us know I would be very intrested in converting to the Subie R180s.
I have done my homework and the 06+ STIs come with the R180 TORSENS in the rear diff. and have the 115mm ring gear. They offer a 3.7, 3.9 4.11 R&Ps on diff makes and if you want to run older Nissan 115s you will need to change the mounting bolts (fine vs coarse threads) or retap the nissan ring gear.
A friend who use to run IMSA was telling me that for hard core racing the clutch type is prefered due to the fact the it is adjustable as far as how fast and abrupt you get total lock up, but most racers dont have the tools or expertise to really get use out of the units. How many of us are going to pull your rearend and adjust between sessions or have multiple diffs in varying configs in same ratio (esp useful if raining). Also depending on condition of the discs and springs the units will change there hookup with age/wear, temp and oil viscosity will also have effects on the action. The gear type have the advantage of a more linier action and are not affeced by spring/clutch wear or temp (no adjustability though) also much lower maintance and wear which tranlates to longer life

[Tom Donnelly]

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

Thanks Keith, that's the main thing I've been working on. My turn in on 12 and 1 are off and I'm sawing and lifting in both. Especially 1. And the lifting just increases the sawing. Can't wait till next year.

[Ron Earp]

Hot tip on setting up preload on a Nissan R180 LSD: don't do anything! Eventually we were running the stock 45 ft-lbs of breakaway or whatever it is. .

Riley mentioned this when I spoke to him last week, probably from you guys' efforts. Unfortunately, I think mine was put together back in the late 90s and it is torqued up pretty tight. Have to fix that.

[kthomas]

No need to "fix" anything- it'll loosen upon it's own Bottom line- don't fret over getting big preload numbers as it doesn't seem to help anything.

[MIKEL]

It might be worth your while to have somone who is up on them to go through it. The clutches may be worn or load not set up right. Like my freind said they are twitchy if set up wrong and you may be getting to much lock up at the wrong times. The high torque cars are sensitive to how abrupt the diff locks under loads (ie comming out of corners). Since the Z's are tail twitchy this could be a problem.

[Ron Earp]

No need to "fix" anything- it'll loosen upon it's own Bottom line- don't fret over getting big preload numbers as it doesn't seem to help anything.

I dunno - it has a full race season on it now and it is just as tight as it was on day one. I've got a stub axle that was cut off and has a hex head on it so you can attach a torque wrench to it. If I want to check the breakaway torque what do I do - put the stub axle in on one side, put the other side on the ground, and see how much torque it takes to turn the stub axle?

[Xian]

I know it's completely apples: oranges but quite a few of us in the Honda camp (ITC, ITB, and ITA cars) as well as some Miata's run Eckerich's diff's with plenty of success. I'd definitely suggest talking with him about making one for you.

Christian