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What's a Nopel?
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I have seen the following numbers (are there more?) on GT Speedometers"

W=897
W=1020
W=1062

I'm assuming that these numbers have something to do with the speedometer's MPH ratios.

Also, when looking at the housing of 2 different speedos (W=1020 vs W=1062),
I've noticed that they look very different.

I used to think that GT speedometers were interchangeable, but now I'm not so sure.

Can anyone shed any light?

Thanks.
Marc
 

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Old Opeler
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"W" munbers

It signifies something to do with the factory calibration and speed correction. Put "speedo" into the search box and several references will turn up.

Apparently, the W=1062 is required for a Getrag 5-speed gearbox conversion.

Looks like a speedo should only be replaced with one having the same "W" number as the original one in the car from the factory.
 

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Administrator
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That's the calibration number. I think it's the number of revolutions per mile (or Km) the cable spins. The drive gears on the tranny are color coded to go with the speedo head.

Automatic GT --> W=1062 --> "Blue" drive gear. (Used in Getrag conversions)
 

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Super Moderator
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I moved this to "Group 1 - Electrical" because that is where gauges go in the FSM.

Here's an answer that I was given on the classicopels site:

Subject: Fwd: Re: [Opel] speedo help

--- In [email protected], [email protected] wrote:

This has been explained in an earlier e-mail by Uwe Klippert:

Very easily the correctness of the speedometer is to be checked. On the speedometer is the so-called "Wegdrehzahl= way [road] number of revolutions: W=... " indicated.
This number is the number of revolutions of the speedometer cable, if the vehicle moves exactly 1000 m [KM]. The " way number of revolutions " at your car can checked, if you know:
- the dynamic free length (U) of the tire, [circumference]
- the reduction in the rear axle (ia) and
- the gear reduction in the transmission (it) .
- The reductions in the transmission are
red: 7/18,
yellow: 7/19 and
blue:7/20

Typical values for U are about 1795 mm for 185/70 13R an for Ia:
3.67,
3.44,
3,18
So finally:
W = (1000 * ia * it)/U

Example:

W = (1000 * 3.44 * 7) / (1,795 * 20) = 671

The theoretically correct way number of revolutions W in the speedometer should be 671.
So you should change the coloured driven gear in the transmission to reduce the deviation.

Uwe

Of course we are using miles here, so the correct equation for your case is:

W = (1609 * 3.18 * 7) / (1.795 * 20) = 998

This is assuming you have a blue cog wheel in the speedo pick-up. Thomas 72 Rallye
 

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"W" number to gearing relationship!

Gary said:
That's the calibration number. I think it's the number of revolutions per mile (or Km) the cable spins. The drive gears on the tranny are color coded to go with the speedo head.

Automatic GT --> W=1062 --> "Blue" drive gear. (Used in Getrag conversions)
More accurately put, this is ANY Opel with 3.44 rear end and standard size wheel/tire combo!

:cool:
 

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Not to confuse this issue, but OGTS was sure that the blue and 1062 were to be used with the Getrag. Or could I have used different combinations? Just a note, there are speedos with no w # and steel drive gears for the tranny end instead of colored plastic. I don't know what year they came out of but I have 1 of each. I also pulled my blue gear from a 4 speed not an auto.
 

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Old Opeler
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Good Info!

That method of working out the "W" number can be reverse engineered to get the speedo drive ratio pretty close for other ratio diffs ( and even other tyre sizes and gearboxes! ) for use with original Opel speedometers.

Like the 3.9:1 ratio of an Impulse diff. Even if there is another make/type of auto or manual gbox the formula can be used as long as the speedo drive ratio is known.

Nice one Kwilford:)
 

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PrOpeller
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GTJIM,

Could you show me how to reverse engineer the equation for a 4.22 axle, stock tires, and a getrag?

I tried to figure it out and got W=724 (???) with the blue gear. But I'd really like to match the closest available "W=number" to one of the three gear colors and end up with a combination that will come close to showing my actual speed. Thanks!
 

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Old Opeler
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Mathematical Machinations

PROPEL,

The 4.22 diff ratio changes things dramatically:

W = 1609 * 4.22 * 7 / 1.795 * 20

= 47529.86 / 35.9

= 1323.95 which is way out of range of existing speedos.

However; help is at hand. That diff ratio is for 1.5 & 1.9 engined Kadetts and they have a 5 - tooth drive gear on the tail shaft.

W = 1609 * 4.22 * 5 / 1.795 * 18

= 33949.9 / 32.31

= 1050.75 which falls between 1020 and 1062 so either could be tried with 1062 giving the best ( theoretical!) results.

So with a 5-tooth Kadett drive gear on the mainshaft and an 18-tooth (red) plastic gear you are close.

The only other variable you have to play with is the actual distance the tyre travels in one revolution which has been assumed as 1.795 metres for a 185/70 13R tyre in these calculations. If you are using 165 x 13 tyre it will change a bit and you need to recalculate with your real tyre rollling distance.
 

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W 1062 MPH speedo

I have a spare W1062 speedo,
and in need of some other spare parts. Wanna trade? drop me a line
 

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Your Noble Friend ;-)
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4,380 Posts
speedo gear calculator

for everybody who wants to know it exactly: I translated all the knowledge from above into one Excel sheet, so everybody can easily play around with different speedo gears and speedos.
Here's a short manual how to use the chart:
  • you can change all cells with a green background;
  • in line 2, type in the actual speedo drive gear color. Acceptable values are "red", "yellow" or "blue";
  • Excel will "translate" the color in an actual teeth quantity in line 3;
  • In line 5, type in "5" if your screw wheel in the gear box is from a Kadett 1.5 or 1.7, or type in "7" for any other model (see post from GTJim);
  • In line 6, type in "1000" if your intended speedo model is supposed to be metric (km/h) or "1609" if its supposed to be US (MPH);
  • in lines 9, 10 and 11 you can put in the "W" numbers from 3 different speedos to compare;
  • Line 14: your rear axle gear ratio;
  • Lines 15, 16, 17: tire size. Type in 185, 70, 13 for a 185/70/13 tire, 205, 50, 15 for a 205/50/15 tire and so on. Watch out: a 165/13 tire is in fact a 185/85/13 tire and needs to be entered as 165, 85, 13!
  • Line 19: the normal slip factor for your tire is 3% (resulting in a 3% circumference or speed loss to the theoretical circumference), but if you want to you can change it.
Your results:
  • Line 8 shows you the necessary "W" number for the speedo you need for your application, highlighted in blue letters.
  • Since you can not pick an exact "W" number, you might want to look in comparing different speedos, and how close you will come with different drive gears, rear axle ratios and tire sizes. The numbers in line 9 to 11 give you the actual speed and odometer deviation to the correct number. Example from the existing table, column "D": If you used a red drive gear with a "7" teeth screw gear and a km/h speedo with the rear axle ratio and tire size shown, you need a speedo with W=843 (does not exist...). Your speed would show 5% high (plus sign) on a W=800 speedo, 18% too slow (minus sign) on a W=990 speedo, and 30% slow (minus) on a 1094 speedo. This example was created for my "new" Kadett which got a 3.89 rear axle. I will actually go with a yellow gear and an existing km/h speedo. Deviation as of H9: zero %, but showing km/h!
If you find incorrect values or have additional ideas to incorporate into the table, please let me know!

Dieter
 

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Your Noble Friend ;-)
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Oh, and if you use my table and get a speeding ticket, tell the officer "It's all Dieter's fault!"
 

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1971 GT
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Dieter - That's great!

And it tells me that with my tires (225/50/15) and stock rear end, the 660 km/h speedo is only 1% off with a blue gear, which I got with my Getrag.

Unfortunately, I have a w=557 (kmh) and a w=1062 in my possession. 1062 is just as accurate, but I'd like to stay metric.



Anyone got a 660 they'd like to part with?

Corey
 

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Simplified

Stock U.S. Export Opel Speedometer Gradient Application:

w=897
Opel GT 1.9 (with early 4-speed manual transmission, brown plastic gear)

w=1020
Opel GT 1.1

w=1062
Opel GT 1.9 (with late 4-speed manual transmission, blue plastic speedo gear)
Opel GT 1.9 (with automatic transmission, all years, blue plastic speedo gear)

Optional:

w=1062
Opel GT with aftermarket 5-speed GETRAG conversion (with swapped blue gear)

Note:

There are design differences, between some of the 1968-1969 GT speedometers (integral cable inlet housing, "w" etched on rear case)
and the later GT speedometers.

"Metal" speedometer gear, used on 1968 Kadett 1.5 and 1.9's
with "early" 4-speed manual transmission.
 

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Opeler
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Hi I have read through and am confused.

If I explain what I have, can someone assist.

I have a 1969 Opel Gt which was an auto that I have converted to 4 speed which I am now converting to Getrag 5 speed. I have a speedo with 150 miles an hour on it which has W1062 stamped on the back. I have just bought the longer 5 speed speedo cable and the car is on stock wheels with 185/80 tyres on it and as far as I am aware the standard diff. The Getrag I have bought has a yellow speedo gear in it.

Do I just need the the blue speedo gear or is there more to do?

Also can anyone give me any pointers on how to remove the yellow gear and put the blue one in?
 

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If your tyres are truly 185/80 then they are quite a bit taller than the original size which was 165/80. Are you sure they aren't 185/70? The 185/70 is almost the same diameter as the original tyres?

Harold
 

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Opeler
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I might have got that wrong. My rims and tyre are being powder coated and am running the closest to the original 165SR so let's just assume I am running stock wheels and tyres.
 

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Looking for a Metric Speedo W=660

I know its unlikely, but does anyone happen to have a spare metric speedo (W=660) lying around?

My GT originally had the W=1062, miles per hour speedo but the PO changed it to a W=897 (the numbers are way off!). Since we've gone metric in Canada and I have to change speedo anyways, I thought I might as well go for the W=660.

Thanks,

Harold.
 
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