I never thought that I would devote an entire blog post to the lowly cog, but this really is a cracker:
We’ve spared neither cost nor effort and can now, *drum roll*, offer you an edelschmiede reproduction of the blue speedometer gear for cih transmissions! As customers ewre constantly asking after this piece, we decided to reintroduce this worm gear to the market! For those not in the know: the blue speedometer gear has 20 teeth, then there is a red one with 18 teeth and the golden mean, the yellow speedometer gear with 19 choppers. If you drive a very short transmission, or if you have very small tyres on your Opel rear-wheel-drive, then the blue helical drive gear is the best choice, when a precise speedometer reading is important to you.
However, this subject is naturally not that easy! The refit depends on the currently installed speedometer gear and the current speedometer deviation. – So how do you identify the required gear?
Attention: Theory begins here!
Install a sat nav in the vehicle and drive exactly 100km/h, as shown on the sat nav. What speed is shown on the good old Opel speedometer? Too much, too little? Thus, you have a reading on the deviation percentage; As an example, lets assume that at exactly 100km/h (according to the electronic assistant) the speedometer in your Kadett C GT/E only shows 95km/h. The transmission currently has a speedometer system installed using the yellow gear. Now you know that you need to install a drive that shows 5% more than the current drive. In this example, the red worm gear would be appropriate, which has 18 teeth. In contrast to the yellow gear, which with its 19 teeth is exactly 1/19 slower, this gear corresponds to an exact 5.26%, or 5% difference when rounded. Here is a list of the different colours and transmissions of the available gears:
- Helical drive gear, 18 teeth, red, Opel – No. 724431
- Helical drive gear, 19 teeth, yellow, Opel – No. 724432
- Helical drive gear, 20 teeth, blue, Opel – No. 724433
The maximal drive difference that can be achieved in the speedometer is around 10%. When your Getrag or ZF currently has a red helical drive gear installed and the old Opel shows 110km/h when actually driving 100km/h, then install the blue variety and you’ve saved the situation.
But what to do when the speedometer shows speeds 25km/h faster than it should?!? In that case, you should set about trying to understand the travel-distance indicator of the speedometer. This number is displayed on the dial-face of the speedometer, and can be called W=743 in Manta B Gt/Es, as an example. But that’s a topic for another day…
All done, that’s the theory done and dusted!
So yeah, I hope I was able to shine some light on to the dark side of the speedometer. And in case I haven’t, then I am always pleased to receive your reactions and further questions, no problems@
Naturally, as always I’ve saved the best till last. All gears, as well as complete speedometer drives can of course be purchased. The following options are available:
- Speedometer gear in red, with seal set
- Speedometer gear in yellow, with seal set
- Speedometer gear in blue, with seal set
Also available complete
And for those who prefer things ready for installation, with a proper galvanised speedometer drive steel cylinder and installation set:
- Speedometer gear in red, complete with installation set
- Speedometer gear in yellow, complete with installation set
- Speedometer gear in blue, complete with installation set
For those of you are already decided, we are willing to offer you a no way! – deal on all these parts! On direct orders via email to firstname.lastname@example.org there will be a 10% discount! But only until the 17.11.2013. So: start work on your drive systems, so that winter won’t get too dull 😉
Greetings, as always, from the edelschmiede