The R4 is fast ... but my speedometer/odometer are faster

[Bertl]

Hello everybody,

after the first test runs it seems that my speedo/odometer are fast by ca. 15% ... I did ca. 55km today, but it had ca. 68 on the clock afterwards ... the speedo is fast as well.

We have mated a '78 motor and gearbox with a '87 body shell ... is there a different speedo gear in the gearbox, and can it be exchanged?

Thanks

Robert

 

[petak]

There are few speedo gear ratios depending on gearbox tipe
Gearbox can be 354 tipe (earlier models) or HA0 tipe (later model)
On my GTL from 1992 gearbox is HA0-146.
speed gear ratios are different depending on gearbox suffix.

I can send you R4 gearbox ratios in pdf if you give me email where to send it.

Other less complicated solution is check which tires do you have on car.
R4's speedo is calculated according to 135/80/13 tire (or 145/80/13 - R4 F4/F6)

If you have some other tire dimension on car there can bi difference in millage and speed that speedometer show.

 

[DavidN]

The actual question should be how to change / adapt the speedo ratio to your gearbox.
If I remember correctly the topc has been discussed on the German board a few months back. Some of the "old dogs" there even had a solution. It included dismantling of the instrument cluster and adapting some of the inner gear wheels.

 

[Bertl]

David, I think this was in the context of adding a trip recorder to the R4's speedo ... I'll re-read that thread, thanks for the reminder.

Robert

 

[DavidN]

I meant a different thread a few months back.
Context was the 10 percent speedo fast reading of the F6 engine-gearbox-setup and putting a GTL box in a van or some engine upgrade.

 

[Bertl]

OK ... here are the tags of the two gear boxes involved. The one that's still on the gearbox is from the red car the bodyshell (and speedo) came from.

I've removed the tag from the other gearbox that came from my original blue car.

Both are 354/HA0 146.

As I have never driven the red car in a working state, I must presume that the speedo was fast all along, and that the old style speedo is more accurate.

BTW the car is on size 135 tyres at the moment.

Robert

 

[renoir cigar]

What happened to the red car? Looks like it had an anvil dropped on it!
Crikey!

 

[Bertl]

An elderly lady decided on an icy day that the ditch was a much more desirable location than the road
I haven't checked the chassis, but the shell was OK apart from the bonnet and the left front wing.