Has anybody purchased and installed a speedometer gear reduction after the angle drive on the ZF? I need to make a correction on my speedometer and I already know what the error is.
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How much is the error?
You will most likely find you have a mismatched angle drive and speedo unit.
There are actually four ratios available for the angle drive two each for VDO and Veglia Borletti, depending whether your speedo is km/h or mph (ratios are 1.1:1 or 1:1) The back of your speedo will also be stamped with a ratio either 1600 rev/min or 1200 rev/min, knowing these you can work out which drive gear ratio you need.
You will most likely find you have a mismatched angle drive and speedo unit.
There are actually four ratios available for the angle drive two each for VDO and Veglia Borletti, depending whether your speedo is km/h or mph (ratios are 1.1:1 or 1:1) The back of your speedo will also be stamped with a ratio either 1600 rev/min or 1200 rev/min, knowing these you can work out which drive gear ratio you need.
Yes, I have a custom gear set just after the angle drive on the ZF.
The gear correction drive was set up in the following manner:
1) I drove down a highway where there were the little square km or mile numbers posted. They are usually at every 2 km or 2 mile intervals. I have seen them at 5 mile or 5 km invervals.
2) At one of those markers I set my odometer to "0". I noted the km (or mile) marker number. I drove a distance. The longer the distance the less the error. I drove 100km (while on a drive to Montreal). I noted the odometer reading.
3) If the odometer says that you have driven 115 km (or miles) when you know in fact (from the km (mile) markers that you drove 100 km - You know that you will have to correct your speedometer output by a gear set with a 100/115 reduction or 1/1.15
Recall that the speedo and odo are driven by the same input.
This is what I did. Works well.
HTH
B.G.
The gear correction drive was set up in the following manner:
1) I drove down a highway where there were the little square km or mile numbers posted. They are usually at every 2 km or 2 mile intervals. I have seen them at 5 mile or 5 km invervals.
2) At one of those markers I set my odometer to "0". I noted the km (or mile) marker number. I drove a distance. The longer the distance the less the error. I drove 100km (while on a drive to Montreal). I noted the odometer reading.
3) If the odometer says that you have driven 115 km (or miles) when you know in fact (from the km (mile) markers that you drove 100 km - You know that you will have to correct your speedometer output by a gear set with a 100/115 reduction or 1/1.15
Recall that the speedo and odo are driven by the same input.
This is what I did. Works well.
HTH
B.G.
quote:Originally posted by andriyko:
Yes, I have a custom gear set just after the angle drive on the ZF.
The gear correction drive was set up in the following manner:
1) I drove down a highway where there were the little square km or mile numbers posted. They are usually at every 2 km or 2 mile intervals. I have seen them at 5 mile or 5 km invervals.
2) At one of those markers I set my odometer to "0". I noted the km (or mile) marker number. I drove a distance. The longer the distance the less the error. I drove 100km (while on a drive to Montreal). I noted the odometer reading.
3) If the odometer says that you have driven 115 km (or miles) when you know in fact (from the km (mile) markers that you drove 100 km - You know that you will have to correct your speedometer output by a gear set with a 100/115 reduction or 1/1.15
Recall that the speedo and odo are driven by the same input.
This is what I did. Works well.
HTH
B.G.
Thanks for the information. I have the calculations worked out using my GPS and the actual speedometer error is 15% fast. That seems like a lot, but that is what it worked out to and the odometer is the same. I have found some cable gear reductions, but don't know if they will attach to the Pantera cable.
In fact my error was around 15% as well.
I had a custom automobile instrument shop make the gear reduction drive. I gave them my angle drive and told them to make it fit on the end.
B.G.
I had a custom automobile instrument shop make the gear reduction drive. I gave them my angle drive and told them to make it fit on the end.
B.G.
quote:Originally posted by andriyko:
In fact my error was around 15% as well.
I had a custom automobile instrument shop make the gear reduction drive. I gave them my angle drive and told them to make it fit on the end.
B.G.
I found a speedometer shop that can supply an in line cable gear reduction. I will have to send them the cable and mark where to make the splice for the gear box, but this can be done to make the correction I need. If I don't get this done before the Las Vegas event this year, there is always the good old GPS on the dash. There is no question about how fast you are going with one of those.