Speedometer cable engine problem

[torito]

Hello,

I've an Opel GT-AL 1969 german model.

I've a problem with my speedometer (it's in Km/h here in Europe). When i'm driving at 70 miles/h, the instrument shows 90 miles/h !

For sure it looks impressive but it's really disturbing and can lead to major troubles on the road (especially here in Europe with police )

The engine is the 1.9L original engine. The speedo has W-660 written on it.

Where do you think the problem is ?

Thanks a lot for your help, Bye

Torito

[tunepipe911]

Torito,
could be the wrong plug in the gearbox(where cable is connected )?

[BQS4]

Originally Posted by tunepipe911 Torito, could be the wrong plug in the gearbox(where cable is connected )?

Just to clarify what Rudy is trying to say, there's different gears where the speedo cable connects to the trans. They are colored. You might be able to tell just by unscrewing the cable connection at the trans and look at the center where your cable goes. I know that there is a red gear, a blue gear and a yellow gear. Beyond that, someone else will have to chime in.

[tekenaar]

Originally Posted by torito Hello, I've an Opel GT-AL 1969 german model. I've a problem with my speedometer (it's in Km/h here in Europe). When i'm driving at 70 miles/h, the instrument shows 90 miles/h ! For sure it looks impressive but it's really disturbing and can lead to major troubles on the road (especially here in Europe with police ) The engine is the 1.9L original engine. The speedo has W-660 written on it. Where do you think the problem is ? Thanks a lot for your help, Bye Torito

OK, first some speedo basics . . .

Speedometers base their function on distance traveled divided by time (Km or MPH). How this is done is determined by measuring the number of wheel/tire revolutions per calibrated unit distance on the speedometer, i.e. how many times you must turn the tire circumference distance per unit speedo distance (mile/km), and inscribed on your speedo as "W=xxxx" (Wegdrehzahl = 'road revolution count').

You can immediately see that, even with the identical gearing, this must be different for the KMH and MPH speedos, mile = 1.6 Km. So, while the speedo drive gear inside the transmission tail shaft is the same in all units, the correct speedo drive ratio is determined by both the plastic driven gear at the speedo cable tranny end and the calibration of the specific speedo used, i.e. units measured, Km/Miles, and the speedo's calibrated "W=" number . . .

Your speedo accuracy is dependent on all these factors being in proper ratios with each other. Even with everything 'stock' from the factory, just changing from original tire size (165/80-13 to 185/70-13) will affect the original speedo accuracy. Changing out just the speedo from a calibrated KPH system for an MPH speedometer throws everything out of wack . . .

To further complicate things, I have two GT MPH speedos here with "W=" numbers of "1062" and "897"! . . . one of them for the 1.1 GT (4.11 rear axle), the other for the 1.9 GT (3.44 rear) and the remainder of the tire turns difference taken care of by a different plastic driven gear in the tranny.

[2 Fast 4 U]

Originally Posted by BQS4 .........I know that there is a red gear, a blue gear and a yellow gear. Beyond that, someone else will have to chime in.

And there is a grey one as well

[torito]

Hello,

Thanks a lot for your extremely fast help ! I'm going to check those colors.

I changed the tire size recently but in fact the problem has started since the earliest beginning even with the original tires/wheels.

I'm going to check tomorrow where that cable is going to.

One latest question. Could such problem be also related to the speedo instrument itself ?

Thanks a zillion times !!!
Bye, Francis

[torito]

Hello again,

I checked and all the necessary cables are connected.

My GT has a speedo W660 installed. Someone told me that it could be necessary to replace it with a W557. It looks like the W557 may be the solution to my problem since my GT is a 69 german model.



Has anyone here replaced his speedo W660 by a W557 due to the same problem ?

Thanks a lot, Bye

Torito