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R32 gtst speedo out by 10kph

Kyer32

By Kyer32,
in General Maintenance

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Duncan Grand Master

Duncan

Posted
Posted

It is normal for a speedo to read 0-10% high (unfortunately), intended by manufacturers and ADRs (although not in this case) to ensure your speedo does not read low if your tyres are worn.

Speaking of which, what size tyres do you have on the rear, and what does they tyre placard say you should have? you can use this https://tiresize.com/calculator/ to determine what % difference that is causing

Personally, when I buy tyres for a car I buy a size that will bring the speedo back to being more accurate; it if it reads 5% high I buy tyres that are 5% larger diameter. If you had an electronic speed sender like R33 onwards, the other option is to add a speedo adjuster but that won't work in R32. Finally, you  might be able to find a different sized gear for the speedo sender but that will be limited to what already exists (and I don't know what sizes do)

GTSBoy Grand Master

GTSBoy

Posted
Posted
7 hours ago, Kyer32 said:

so I need a new speedo cable 

Nope.

The seal is in the drive. A new cable would just fill up and continue to convey oil to the speedo head.

To check if this is what is happening, take the cluster out, dismantle the speedo and have a look. You probably don't even have to dismantle it. If there is oil coming up the cable, the drive into the speedo will be grossly greasy.

I had to manually (and delicately) clean the gunk out of my speedo.

Kyer32 Rookie

Kyer32

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On 8/1/2025 at 6:29 AM, Duncan said:

It is normal for a speedo to read 0-10% high (unfortunately), intended by manufacturers and ADRs (although not in this case) to ensure your speedo does not read low if your tyres are worn.

Speaking of which, what size tyres do you have on the rear, and what does they tyre placard say you should have? you can use this https://tiresize.com/calculator/ to determine what % difference that is causing

Personally, when I buy tyres for a car I buy a size that will bring the speedo back to being more accurate; it if it reads 5% high I buy tyres that are 5% larger diameter. If you had an electronic speed sender like R33 onwards, the other option is to add a speedo adjuster but that won't work in R32. Finally, you  might be able to find a different sized gear for the speedo sender but that will be limited to what already exists (and I don't know what sizes do)

 

1 minute ago, Kyer32 said:

My tyres are 215/45/r17 the 32 is a type m

 

Kyer32 Rookie

Kyer32

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On 8/1/2025 at 7:21 AM, GTSBoy said:

Nope.

The seal is in the drive. A new cable would just fill up and continue to convey oil to the speedo head.

To check if this is what is happening, take the cluster out, dismantle the speedo and have a look. You probably don't even have to dismantle it. If there is oil coming up the cable, the drive into the speedo will be grossly greasy.

I had to manually (and delicately) clean the gunk out of my speedo.

So if anything it’s be the seal speedo drive sorry it’s being awhile since I worked on one of these is the drive connected to the gearbox or behind the cluster 

PLYNX Mentor

PLYNX

Posted
Posted

Yep ! 

Cluster out first.

Dismantle.

Check for oil grease. If oil and grease = clean.

Then check seal at the drive coming from the gearbox. 

Seal broken  = change seal.

Doing it the other way around it will again push grease/oil back into the cluster and then your gonna have to do the cluster clean all over again !

 

Kyer32 Rookie

Kyer32

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On 7/1/2025 at 11:26 PM, GTSBoy said:

I would guess the seal has gone down at the speedo drive and gearbox oil has crept up the drive cable sheath and fouled the speedo head.

 

On 7/1/2025 at 11:32 PM, niZmO_Man said:

Your car was auto before? You have different diff ratio (auto vs manual i think? or n/a and turbo?)

 

1 minute ago, MBS206 said:

What makes you guess that tyre size specifically?

Just tried researching factory type m spec that’s all I can find 

niZmO_Man Grand Master

niZmO_Man

Posted
Posted

Search for your VIN in gtr-registry.com and see what it left with from factory. There's 4.3:1 and 4.11:1 diff ratios IIRC, can't remember what models had what.

Also could be tyre size, by factory the speedo reads a tad quicker >80 km/h but constantly out be 10 km/h is weird.

Maybe someone wound the odometer back, and accidentally bumped the needle up?

Kyer32 Rookie

Kyer32

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1 hour ago, niZmO_Man said:

Search for your VIN in gtr-registry.com and see what it left with from factory. There's 4.3:1 and 4.11:1 diff ratios IIRC, can't remember what models had what.

Also could be tyre size, by factory the speedo reads a tad quicker >80 km/h but constantly out be 10 km/h is weird.

Maybe someone wound the odometer back, and accidentally bumped the needle up?

Well found out it’s a 60th anniversary gtst from that it came with 205-55r15

-Jimmy- Mentor

-Jimmy-

Posted
Posted

Interesting, I haven't read about the issue with oil getting into the speedo in the cluster before. I'll have to take more notice with mine.

The speedo on my R32's when I've run factory diff and tyre size have never been accurate as far as I can remember.

On 1/12/2025 at 9:44 PM, GTSBoy said:

No R32 GTSt had 15" wheels. 205/55-16 was standard GTSt fare.

4.36:1 is standard R32 turbo auto diff. I think the manual was too, not 4.11.

4.11 and 4.08 were R33 namual and auto respectively.

The non Type-M GTS-t did come with 15" 5 stud wheels and smaller brakes, but that's less than 5% of them. :)

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