Speedo reports faster than actual speed

[HadesOmega]

My GVR4 reports +10mph higher than actual speed. I found it strange how my car says I'm going like 70mph and cars are passing me so I checked it with a GPS one day and found out it 10mph higher. Does anyone know the cause for this and is there a way I can adjust it like get a different speedo gear drive or something?

 

[thomcasey]

Whats your wheel/tire combo measurements?

 

[HadesOmega]

Ahh I forgot about the tire size

It has EVO8 wheels with 245/40/17s

I put in the sizes with the stock 195/60/15s in the tire calculator and it says they're the same size though maybe reports 1mph faster.

Maybe if I change to a taller profile tire like a 45 it will read closer to what it should be but it'll probably be off by +5 still.

 

[iceman69510]

1g trans and speedo gear maybe? They are different (though I am not at this point thinking about which way).

 

[HadesOmega]

Hmm that maybe the problem are the GVR4 and 1G DSM speedo gears interchangeable?

 

[iceman69510]

Yes, IIRC they are one tooth different maybe. I put the 1g in my car because I have 225 45-17 tires on, and they are closer to the rolling diameter of the 1g with 16" wheels than the stock VR4 diameter.

 

[HadesOmega]

Cool I guess the search for a 1G Speedo gear drive begins thanks =)

 

[FlyingEagle]

I looked up a 4wd D27A model and the speedo gear (driven) in the trans case top, is MD728826.

JnzTuning.com shows just over $21 US if they can get the part. The part listed N=29 which has to be the tooth count.

The same gear in the Gvr4 is MD728827, and listed as N=30, so 30 tooth count.

As Ice suspected, it is a single tooth count difference. Same price.

 

[strokin4dr]

Good info here!

 

[HadesOmega]

Just a followup to this topic. I finally got around to installing A gvr4 speedo gear that I got. When I took the current one out it had a 29tooth gear and the gvr4 one I had had a 30tooth gear. Swapped them out and now my speedo is off by +12 now so it made it worse. I guess I should have figured since the teeth went +1 it would spin slower.

Anyway I noticed my speedo needle settles on the 15mph mark. Is this normal? Maybe I should open it up and move the needle to the 5mph mark.

 

[FlyingEagle]

Never seen a speedo that doesn't sit at the needle when it should be at rest, unless something is amiss or someone had the gauge face/needle off for some reason and they goofed at reinstalling the needle. The needle should sit lower at rest as it only moves up when the reed switch is activated and the cable in the back of the cluster is actually spinning.

 

[HadesOmega]

Yeah the previous owners have been doing some goofy stuff to this car =(