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Bows

Member Since: 07 May 2012
Location: Wales
Posts: 513

Speedo accuracy

I have an old Land Rover 110, which is fitted with a 200tdi engine from a defender, I have now fitted a 1.22 transfer box from a discovery to replace the standard 1.6. ratio. The speedo cable is obviously linked to the gearbox therefore have the new transfer box ratios knocked the speedo out of calibration. The speedo is indicating a significantly slower speed to the speed indicated by a GPS but I do accept that this could be due to a number of reasons!! The vehicle is totally standard otherwise.

cheers

11th Jan 2014 6:27pm

custom90

Member Since: 21 Jan 2010
Location: South West, England.
Posts: 20298

Are you out about 2mph or a lot more? ⭐️⭐️God Bless the USA 🇬🇧🇺🇸 ⭐️⭐️

11th Jan 2014 6:31pm

Bows

Member Since: 07 May 2012
Location: Wales
Posts: 513

More, about 10mph out

11th Jan 2014 6:52pm

lukev01

Member Since: 24 Mar 2012
Location: Bedfordshire
Posts: 412

2013 Defender 110 Puma 2.2 XS CSW Santorini Black

Not to worry!

Once you have used GPS/Satnav to check what your speedo is reading at 30/40/50 etc. either just remember "true speed" or you could put a marker on your speedo.

My S2A is doing 30 mph when the speedo says 40 and 40 when it reads 52 and I have not got a ticket yet. I have always assumed it is due to the 31 x 10.5 x 15 tyres on it. 1970 Series 2A 88"

11th Jan 2014 7:00pm

Bows

Member Since: 07 May 2012
Location: Wales
Posts: 513

Thanks Luke, establishing my speed isn't a problem, what I would like to achieve is having the speedo working as accurately as possible because I like to calculate mpg etc.
I am considering having it recalibrated, I am aware of the effect tyre size has on speedo readings but I was hoping to find out whether transfer box gearing also has an effect .

11th Jan 2014 7:07pm

custom90

Member Since: 21 Jan 2010
Location: South West, England.
Posts: 20298

I would imagine the transfer box ratio would have an effect though but I am no expert. ⭐️⭐️God Bless the USA 🇬🇧🇺🇸 ⭐️⭐️

11th Jan 2014 7:10pm

lukev01

Member Since: 24 Mar 2012
Location: Bedfordshire
Posts: 412

Bows, that makes perfect sense

I am sad enough to calculate mpg on my Defender.

Even if I were to try on the S2A, I don't think I want to know what I really get from the 2286cc petrol. 1970 Series 2A 88"

11th Jan 2014 7:26pm

LandRoverAnorak

Member Since: 17 Jul 2011
Location: Surrey
Posts: 11324

The speedo will be out because of the transfer box change. There is an interchangeable cog in the speedo drive that's calibrated for the different applications (Disco/Defender on two different tyre sizes). They are colour coded but I don't know, off hand, whether there's one that would suit your particular gear ratio/tyre size combination. Darren

110 USW BUILD THREAD - EXPEDITION TRAILER - 200tdi 90 BUILD THREAD - SANKEY TRAILER - IG@landroveranorak

"You came in that thing? You're braver than I thought!" - Princess Leia

11th Jan 2014 7:59pm

Bows

Member Since: 07 May 2012
Location: Wales
Posts: 513

Thanks Anorak, I'll have to look into that, disco speedo settings will be thrown out by 7.50 16 tyres so it wont be straight forward.
Has anyone got any experience of that?
cheers

11th Jan 2014 8:07pm

ashtrans
Site Sponsor

Member Since: 08 Nov 2008
Location: Harpenden
Posts: 257

If you use the speedo drive gear out of the old transfer case, then the speedo will stay true,

Dave Dave

11th Jan 2014 10:43pm

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