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OBX LSD users, would you do it again?


letitsnow

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I am in desperate need of an LSD. I currently make about 270rwhp and 340ftlbs of torque, I'm planning on another 100ish hp in the future and would like to account for that. The car is primarily a street car and autocrosser with some trips to the drag strip.

 

You guys that went with the OBX unit, are you happy with it? Would you buy another one? Any issues?

 

I figure that my other options are an aftermarket 240sx 1.5 way, like a KAAZ or Carbonetic. A used 240sx 2 way can be had cheap from the drift crowd. An STi r180, but that might not be the greatest with my planned power increases. I suppose the z31 is on the table but they generally have a bunch of miles for what they cost.

 

I don't think a Quaife is in the budget, a new 240sx clutch diff is pushing it.

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I've done the shim upgrade to a Z31 CLSD. I would probably just install it and not do the shimming if I had it to do over again. I had lots of chatter trouble until I added a total of 3 tubes of friction modifier. It is great now. No ill behavior.

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duragg-thanks for all your advice when I was putting that diff together. It is sweet now. When it was locking - it was like all hell was breaking loose. You'd have not only heard it but also felt it if you had "chatter." It had the feeling of a loose wheel or a flat tire. All good now, but diff is leaking fluid either from a fill plug, the vent, or the cover gasket (new and carefully installed). I was careful not to overfill. Just enough leak to slime the bottom of the diff cover, but not enough to drip, yet. Gonna clean it up real good and shake baby powder all over it to try to find location of leak. I don't want to oil the track and be the cause of a guardrail close encounter.

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Is the shimmed z31 diff still smooth or is it clunky like some of the aftermarket units?

There are two different things going on here: adding clutches to a 300ZXT diff, and shimming. Adding clutches will allow the CLSD to hold down more power and also make it more aggressive. Shimming makes the breakaway torque tighter. Adding the clutches is a very good idea. Shimming is probably not necessary for most people and will make the diff more likely to chatter.

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Won't adding clutches also increase the breakaway torque?

 

I'll keep my eye out for a z31 diff I think, if I can't find a reasonable one, I guess I'll go with the obx.

Yes. The issue is that on the Z31 they ran one clutch per side to drive the axle and then put a big spacer in there to take up the room where the other two clutches should be. If you put too much power to it you'll strip the clutch. By replacing the spacer with the two clutches you will make the diff more aggressive and increase the breakaway torque, but it's really necessary to hold down a lot of power.

 

If you get the NISMO diff or one out of a Skyline they don't have the spacer, so no clutches needed. The Skyline diffs are more aggressive than the Z31 with the clutch upgrade, so you're still not going too crazy with the Z31 upgrade.

 

 

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I installed my obx the other day and it drives like I never did anything.... till I do a burn out!!!! It feels very stable but I havent done any serious cornering on it yet. Still shaking the car down. I plan on autocrossing it but it would be nice to have a 1.5 or 2 way if feasible. For me though , the obx was the cheapest.

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If I might ask, why so much for a likely worn out factory diff when a low mileage used aftermarket diff is the same or just a touch more. If I understand correctly, any aftermarket diff for a 240sx that originally had an open diff will work, right?

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Am I missing something obvious where the z31 diff is better at something than the aftermarket units? My experience is limited to factory units on other cars I've messed with, never aftermarket diffs, so I very well might be missing something silly.

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More aggressive than the helicals and can be shimmed tighter if necessary. On a helical you get what you get, unless you have different pitch helical gears that you can swap out. The aftermarket CLSDs offer the most traction. OS Giken, KAAZ, etc, but the price is high.

Edited by JMortensen
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