28/01/09 - Richard Wattams' Rocklobster Speedo Modification

Here is a real winning modification thats going to become a bit of a legend in the future!

As you may know, Jimny Transfer boxes are under geared for off-road use and a popular modification is to put on a Transfer Box from an SJ, either directly or as part of a RockLobster conversion.....

 

A key problem during the conversion is that you need to provide some sort of connection from the mechanical SJ transfer box to the electronic speedometer. You will read elsewhere on this site (once I have written the article!) that I have solved this problem electronically.

However, we were conversing on the Shropshire Suzuki forum the other day and I mentioned some calculations I had carried out on the speedo  sender system in the standard Jimny.

I calculated that the gear ring that generates the electronic pulses, which has 25 teeth as standard, would need 27 teeth to generate the correct pulse strean for 30/31 inch tyred Jimnys and 30 teeth for 33 Inch tyred Jimnys.

This struck an instant idea in Richard Wattam's mind as to where he had seen a 27 toothed gear "lying around".

It turns out that when you do a RockLobster conversion you throw away one of the output dog gears from one of the boxes and guess what? It has 27 teeth. Here are a pair I have lying around as well!

So with a bit of machining the centre can be cut out to fit the SJ flange, see below.

Then with a bit more machining a nice case/mount for the Jimny sensor can be made.

 

And neatly fitted to the SJ case, giving an electronic speedo feed correct for 31 inch tyres!

 

Now Richard has told me that he does not intend (at the moment) producing these. Instead he is going to produce some CAD drawings which meas they can be made yourself, from what is basically scrap material at scrap prices - fantastic.

As soon as the drawings are produced I will provide a link to them for you