Leroy replied:

apparently the ADR's allow for a 10% discrpency.

to change the speedo gear drive would probably entail removing the extension housing on the gearbox. Is it really worth worring about? When I'm doing 100kph my speedo isn't more than 10% out and I have on 285/75's in a BFG MT and they are a 'large' 285/75. Different brands have different rolling diameters.

Leroy

Truckster (Vic) replied:

I think the 3.0 has electronic speedo, so the gear thing wont work, Think that came up on the patrol forum ages ago.

10% for speedo, but I wouldnt worry, try it with a GPS and see how far out you are.

How much is the engineers? Gotta get mine done too

Member - Sam (NSW) replied:

According to Marks 4x4 Adaptor website (click here), the GU uses a 2 wire inductive sensor for its speedo.

Robin replied:

0% under indication and -6% over Snowy, got Nissan to swap out a new speedo on that one for my GQ before I realized the electroinc speedo had a cal knob on the back.

You probably need to do nothing as GU speedo reads over (faster) about 6% by design.
My 33's almost spot 100 reading=99 actual and 60reading =61 (note speedo is non-linear)

Jaycar convertor kit is lowest cost option - if you don't mind building things

Robin Miller

bobsa replied:

Hi Snowy,
I had the same problem with my 3.0L GU 4
There is no adjustment on the back of the speedo.
The driven gear is very easy to change. Find the sensor on the back of the gear box on the extension housing, there is a 10mm bolt remove that and pull it out a small amout of oil will be lost, I just plugged it with a piece of rag.
There is a small circlip remove this and the cog can be removed and changed to suit your needs.
Here is a list of part numbers for the cogs
32743-74P18..........18 tooth
32743-VB017..........17 tooth
32743-VB016..........16 tooth
32743-VB015..........15 tooth
the original cog in the GU 4 with 17" standard rims is a 16 tooth, went to 285 75 16 and changed to a 15 tooth cog and the speedo now read about 4 km fast.

dan26aus replied:

Hi there Snowy,

I have been thinking about increasing in size on my patrol also, and found something to supposedly suit on ebay. I don't know how to send the link via this site, so if you go into ebay and do a search for a " speedo correction switch" you should get a hit for your patrol. Dunno if they're any good or not but let me know how you go if you decide to try it out. Also i did a comparison on a tyre calculator for you and depending on what size tyre is recommended on the inside of your glovebox, i did the comparison as if it were my patrol which was : recommened tyres: 265 x 70 x 16. compared to 33 x 12.5 x 15 = 6.27% difference & 33 x 12.5 x 16 = 11.17% difference.
If you would like me to send you the link to ebay or the link to the tyre calculator you can send me an email to: dan26aus@aapt.net.au and i would be happy to send it to you........

Good Luck

Dan

Member - JohnR (Vic)&Moses replied:

Snowy as far as the speedo is concerned do you know how far it is out with the original tyres. Mine was out 4kph at 100 indicated under so was actually 96 kph. It's easy enough to work out the percentage difference and 285/75s give it nearly 6% to 101.5 approximately at in indicated 100 dependent on the tyre and tread chosen