ATS 4.23 or 4.44 LSD with power-steering on a 1997 NSX

ScienceOfSpeed notes that the 4.23 final drive kit disables the electric power steering on the NSX. Is this also true for the 4.44 final drive kit? Speaking with ATS over the phone, there was mention of two different kits for the 4.44, one specific for the NA1 and one for the NA2. There's only one kit for the 4.23 (for both the NA1 and NA2), which I'm assuming is part of the reason why it ends up defeating the power steering system in the cars that have it?

As a reference point, the OS Giken LSD 4.44 kit doesn't defeat the EPS system, though that's tested only on the 1995 — 1996 NSXs which also have a different EPS version than the 1997+, though I think this is more so because of the 5-speed only compatibility of the diff.

francisluu said:

ScienceOfSpeed notes that the 4.23 final drive kit disables the electric power steering on the NSX.

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mmm....... I have installed a 4.23 on a 1995, no issue with the power steering. You do need to shim the speed sensor located on the top of the trans that feeds the power steering system, since the 4.23 gear will hit the sensor. I remember using a thin washer to shim it. All was/is fine for many years.

For the 4.23 you need a 1991-94 differential, regardless of the year trans. So I installed a 1991-94 dif with 4.23 in a 1995 and no power steering issues.

The 1997+ power steering is different, so as stated above, this will cause PS issues.

Regards,
LarryB

Resurrecting this thread somewhat, I have a similar question. My car is a JDM 1990 A/T with factory EPS, which has the same part # as the 95-96 cars.

Is the conventional wisdom still that putting a 4.23 ring gear in a 5-speed will work with the EPS as long as you shim the speed sensor from the ring gear? By speed sensor do you mean the "final pick up assy (28820-PR9-004)? It's blanked off on my 5-spd but it looks like I can steal it off of my auto trans once I swap it.

I've been told recently by SoS that the 4.23 gear will not work with *any* EPS, so I'm getting some conflicting info. Perhaps they were thinking of the fact the 95+ cars have the updated differential that won't work with the 4.23 gear, or that 97+ cars have a different EPS part? I am considering putting a 91-94 diff into my 95-96 trans so that I can also do the 4.23.

Thanks in advance.

Calling [MENTION=3729]Larry Bastanza[/MENTION]!

He will know, since he has done all the different swaps.

Any takers :biggrin:?

I just came across this FS thread (http://www.nsxprime.com/forum/showt...-23-final-drive-amp-LSD?highlight=final+drive) where SoS again says the 4.23 ring gear isn't compatible with 95+ EPS systems due to "the different pulse count generated by the speedo gear" which would require a signal modifier instead of a simple mechanical washer on the sensor. I would assume this might only be true with the updated 97+ EPS brain and not the 90-96's?

I'd like to add my experience on this topic: I have a 2005 NSX and it underwent a type R / 4.23 ring gear swap. There's NO EPS issues UNTIL 90 mph. When it hits 90 the EPS light turns on, and if the car was then restarted, it'll lose EPS and revert back to manual. You'll have to do the clock fuse reset (pull / reattach the 7.5 amp fuse under the hood) and everything will be back to normal....until the next time you hit 90.

I didn't have this issue when the car had the OS Giken 4.44, so it may be just the 4.23 problem. Which may be why both OSGiken and ATS have 4.44 final drive for the NA2s. The OSGiken shattered like crazy and was not very driveable on the street. THe type R is much more OEM and smooth. I may have to try the ATS in the future...

That's odd, I've been above 100 MPH with the Type R 4.23 setup and not had EPS issues. Maybe it's because your car is an 05 with a different EPS brain and rack and mine is a first-gen 1990? I also didn't think the system would work with 95+ cars at all since the rack and computer were different but I guess that's not true either?

I suppose I should've updated this thread with my own experience as well, I did a manual swap on my 1990 RHD NSX with a 5-speed trans and the JDM short gears & 4.23 final drive, and kept the EPS system from the automatic. I bought a cheap speed sensor (forgot if it was the NM or NC sensor) and used a normal 10mm washer as a spacer like Larry said and have not had any EPS issues at any speed.

I will say I tried using 2 washers instead of 1, and the EPS light came on immediately because I assume the sensor head was too far away from the differential ring gear to get a good signal. Using no washers/spacers will break the sensor when it hits the ring gear, so the tolerance for the proper distance is quite small. Maybe, [MENTION=26852]Geo05nsx[/MENTION], your sensor is not the optimal distance from the ring gear and you lose good signal above 90 MPH? That would be my best guess, since the diameter of the 4.23 and 4.44 ring gears should be slightly different and the 4.44 might have been the proper distance away.

The >90mph is indeed strange. Isn't the 2005 NSX-R on a factory 4.23? What does it do differently than stock?

RYU said:

The >90mph is indeed strange. Isn't the 2005 NSX-R on a factory 4.23? What does it do differently than stock?

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It doesn't have EPS.

I have 4.23 and type R gears with a 96 ecu and the 5 speed

MaxGeek said:

It doesn't have EPS.

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oh gosh... duh!

Big McLargeHuge , I agree with your assessment. I'm going to have my mechanic check into the speed sensor first. But also the EPS system is different between NA1 and NA2. I'll keep you posted.

I was recently linked this thread again on FB. I wonder if a simple VSS signal modifier intercepting the VSS signal coming out of the speed sensor on the trans will work. This is assuming the fidelity of the signal isn't the problem. Another solution is to upgrade to the S2K EPS rack or going to a manual rack like the Type R.

FWIW: I'm on a 6spd 4.23 Wavetrac and standalone ECU with S2K EPS. So everything is custom BUT working properly.