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I need to replace the LSD on a 1995 (NA series) MX-5. The original diff was a viscous LSD, and over time has deteriorated as I hear they do. It is now essentially an open diff, if I lift one wheel off the ground it seems to apply torque only to the lifted wheel, and I would like to replace it.

I have seen that there are a few different types of diffs available, and of these they come in 1, 1.5 and 2 way varieties. The 2 way diffs seems to be more expensive in general, and I would like to know in what instances will having a 2 way over a 1.5 way be an advantage? 2 way to 1 way? In what applications would having a 2 way be a disadvantage?

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What sort of driving do you do? Track? Racing? Drifting? – Timo Geusch Feb 15 '12 at 18:33
Well, I do primarily track driving. I have not gotten into wheel to wheel racing, I do thoroughly enjoy time attacks! As for drifting, I am beginning to strategically (not accidentally anymore) use limited forms requiring load shifting to position my car in corners to maximize the time I can be on the accelerator. I am by no means incredibly skilled, but am very motivated to improve my skills. I assume that you do some sort of track or racing with your NA? – djdoerr Feb 16 '12 at 0:12
My current one is a mostly daily driver but I'm slowly adding a few bits and pieces for track use (ie improved brakes and suspension and all that). The last two I owned in the UK attended the odd track day. Helps if you have a track within half an hour from home, which I don't anymore. – Timo Geusch Feb 16 '12 at 15:29
up vote 2 down vote accepted

First, as a fellow NA MX5 owner I would simply replace the diff with a Torsen LSD out of an NA 1.8 MX5 and be done with it. It's the most cost effective swap I'm aware of if you actually do need an LSD. Plus it's a fairly strong LSD anyway so unless you're planning to put silly power through it, it should last.

That said, the difference between the LSD types you list are as follows:

  • 1 way locks only on acceleration
  • 1.5 way lock on acceleration and partially on deceleration
  • 2 way locks fully on both acceleration and deceleration

For a track only car I'd consider a 1.5 way LSD, or a 1.5 way/2 way for a drift car. But keep in mind that most of these are clutch type LSDs so they do need maintenance like clutch adjustments that the OEM torsen doesn't need. They also need setting up by someone who knows what they're doing before you can make good use of them.

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I will take a look at the torsen diffs. I need to find a way to drive one with a 1.5 or 2 way to compare to the 1 way. Maybe I should just buy both and test them over time :) – djdoerr Feb 15 '12 at 23:45

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