UK NSX 5 speed gear ratios - JDM or USDM?

[sparky]

Wiki information on NSX Prime says all 5-speed European NSX have same ratios as US domestic market, but has anyone actually checked/measured UK ratios to check if they are USDM or JDM?

Reason I'm asking - some time back I tested/measured ratios on my Australian delivered NSX and concluded they are JDM. My theory is right hand drive NSX's got the JDM ratios, and only left hand drive got USDM.

It's hard to find Australian specific specs on the ratios, but if UK NSX are definitely not JDM my theory may be wrong and I might have to revisit my test measurements :(

thoughts?

[goldnsx]

Wiki information on NSX Prime says all 5-speed European NSX have same ratios as US domestic market
That's not accurate in the Wiki.

91-93 are the same or similar. I recall a slight difference in one gear, maybe 1st?
94-96 the EU versions (ok, Swiss ones) got the JDM gears.

I don't think there's a correlation between gear ratios and LHD/RHD. It has more to do with emissions/noise/speed limit. The continental EU might have the long gears because of Germany's Autobahn. The US maybe because of strict emissions in California. Wild guessing though.

With the gearbox in the car you can measure it quite easily. 2nd ends at 130 km/h (long) or 117 km/h (short) or after 8k rpm in 1st the 2nd gear starts at 4400 rpm (long) versus 5100 (short).

I'm not aware of any other gear ratios than the long and the short ones. So the Australian must have one of these.

[sparky]

thanks goldnsx, good info.
And I'll try those numbers on my NSX. (any excuse to wind out to 8K :)

[Kaz-kzukNA1]

There are lots of nice information as well as wrong ones on the web so you will need to judge the accuracy by yourself.
I also make mistake and/or misunderstand the question that I could post wrong info as well so again, you just need to judge the quality/accuracy of the info for each cases.

Regarding the gear ratio….
Between the shorter/longer gear ratio, the 1st and the 5th gears are the same so the differences are at the 2nd, 3rd and the 4th gears.

With our NSX gbox design, on the main shaft, the 1st, Reverse and 2nd gears are all machined directly on the shaft body itself.
Therefore, if you want to change the ratio, you will be forced to replace the main shaft as well.

Of course, unless you are the original owner, you won't know what was done to your gbox in the past but if someone already had the shorter gear ratio from the factory, it would be very unlikely going back to the longer ratio by replacing many gear parts including the main shaft or swapping with another gbox with longer ratio so following method would be a good starting point.

Please check your gbox no.
If 5MT gbox no. starts with J4A3, J4E3, J4J6, SR8M, very likely to be the shorter gear ratio unless someone replaced many parts including the main shaft to get the longer ratio for some reason.

If it's J4A4 or J4E4, then they left the factory with the longer ratio but there is a chance that someone may have replaced the parts to achieve the shorter ratio.


For both cases, like goldnsx mentioned, you can calculate the expected speed and rpm in 2nd, 3rd and 4th gears unless someone changed the final ratio.


If you have access to Australian spec parts system, you can check the parts diagram for the 5MT mainshaft or the countershaft.
If you look at any of the 2nd, 3rd or 4th gear parts no. and if the last 3 digits starts with -A**, you have the longer gear ratio.

With 5MT shorter ratio gears, the last 3digits would start with numeric no. such as -0**.

Lings Honda parts system displays the parts even for the KU and KQ spec for your area so you may be able to use them by entering the VIN.
Just remember to delete the _pfk from the address bar to get the correct Honda parts no. and not the Lings internal system starting such as PFKL######.


Kaz

[sparky]

Kaz

Wow, amazing detailed info (as usual!).

I'll be checking my gearbox numbers shortly and will let you know what I find.

many thanks

[goldnsx]

You didn't mention so far what are you intending to. Do you think the gearing on your NSX is too long for your driving habits?

[sparky]

Over on the Australian forum in NSX Prime we're having a good discussion about Australian NSX ratios: are they JDM or USDM? With the info above from you and Kaz we'll soon have a definitive answer.

So not planning any changes ... well unless it turns out my spare gearbox is JDM and the one in the car now isn't ! Personally I would prefer driving with the tighter ratios. (plus these days it's getting very risky winding the car out on Australian roads anyway, even 130 in 2nd could cost a license in some states :( whereas 117 would "only" get you a hefty fine)

[UnhuZ]

Hi,

My EUDM NSX was first licensed in 97, but was built early in 95.

It has short ratios from factory.

Thanks,
Nuno

[goldnsx]

The only guys who favor the long over the short gears can be found on the US track forum where the long ratios have some advantage over the short ones at certain tracks.

Your stated reason was one of my reasons to switch to the shorties/4.23 plus the fun factor of course. :)