Speedo reading not accurate

Hi all, I have a 1991 cabriolet GTI, and seem to be having a problem with the speedo reading. For instance if am doing 30 my speedo meter will be showing 40 (10 miles out) I was wondering if anyone has had this issue and have resolved it. TIA.

Could be a few things.
Bigger tires.
Wrong gear in the Transmission
speedo was taken apart to repair and the speedo needle wasn't reset correctly.

I do know that my speedo was 5mph lower than the Radar units I passed and I personally didn't mind that too much.

When you remove the speedo needle off the post to reposition it you place it on the back side of the needle rest, and align it with the dot on the speedo face, then gently lift it over the needle rest and it is usually within 1-4 mph off.

Thanks Briano1234, is this easy to. Do taking the clocks apart and is there a guide to do this?

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I would ask the size of the tires and the style of tranny to verify that the Wheels are correct for the final drive for accuracy first.

Here's a how to repair your flaky water temp gauge, which if you take your clocks apart you may want to do but I will tell you right now, order new light bulbs cause put new ones in prior to putting the cluster back in, and don't forget to plump your main connector… This isn't specifically to repairing the speedo, but the cluster in general.

Repairing your Flaky Water Temp Gauge | Volkswagen Owners Club Forum

As with VW claims for emissions the speedo lies as well and reads about 5mph over in most VW cars I've owned even later more modern stuff.

I would look at the other options before taking the instrument out of the car and moving the needle.

What size wheels and tyres have you got?

What is written on the speedo just below the mileage trip, is it 1540 - Motometer?

Whats the code for the gearbox, is it the ACD gearbox?

You can change the gearing on the speedo cable drive in the gearbox but you do have to be very careful pulling the cable out of the gearbox as the cog can fall off if the little clip has gone missing.

Hi all, sorry not been on here for a while but here are answers to few questions,
Tyre size are 195 50 15
Below mileage is 1540,
Gearbox code is ACD..

Mark1gls you have mentioned that the gear on the speedo cable can be changed if so which 1 is the correct one for me if I need to replace it?

Thanks again all.

The gear in the speedo should be red for the ACD.
Since the gear in the tranny has 15 teeth
You should have a red Drive gear on the Transmission speedo cable end.

Sources.


https://volkswagen.7zap.com/en/usa/rabbit+conv+golf+cabrio/conv/1990-44/9/957-236000/#5

https://a2resource.com/eandt/ratios.html

http://www.cabby-info.com/transmission.htm