JimmyRocks Posted May 23, 2018 Share Posted May 23, 2018 Evening all. Does anyone know which speedo drive gear I need ie how many teeth/which colour. Ford mark 9 gearbox, 5 speed. Do I need more info to find out which? Link to comment Share on other sites More sharing options...
Alastair B Posted May 23, 2018 Share Posted May 23, 2018 If you have a 3.92 ratio diff then it is a 24 tooth Black drive gear, for a speedo with 1000 turns/mile. I have it recorded as Finis part 6011058 on a document I have been researching and adding to Link to comment Share on other sites More sharing options...
SM25T Posted May 23, 2018 Share Posted May 23, 2018 Ask Road and Race 01959 525105 Link to comment Share on other sites More sharing options...
JimmyRocks Posted May 23, 2018 Author Share Posted May 23, 2018 Okay. So is it a given that I have a 3.92 diff? (My talents are limited to twisting the wheel and hooting the hooter) Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted May 23, 2018 Member Share Posted May 23, 2018 No.How to measure final drive ratio... and it does involve twisting a wheel!Jonathan Link to comment Share on other sites More sharing options...
JimmyRocks Posted May 24, 2018 Author Share Posted May 24, 2018 Thanks all. So mine is the 2005 onwards electronic speedo rather than cable. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted May 24, 2018 Member Share Posted May 24, 2018 Electronic from the gearbox or from a wheel?Is it the sort you can recalibrate at the instrument rather than the drive... can you add a photo?Jonathan Link to comment Share on other sites More sharing options...
JimmyRocks Posted May 24, 2018 Author Share Posted May 24, 2018 The speedo I have is one of these: https://caterhamparts.co.uk/gauges/220-speedo-mph-2005-onwards.html?search_query=speedo&results=28 I think.I have a speedo sensor: https://caterhamparts.co.uk/senders/1008-speed-sensor-gearbox.html?search_query=speedo+sender&results=98 the internals of the previous having munched themselves.But the spindle of the drive gear is broken also. From what Alastair B says its this one: http://www.burtonpower.com/24t-speedo-drive-gear-type-9-e-gearbox-gbt9302.htmlDoes that make sense? Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted May 24, 2018 Member Share Posted May 24, 2018 Anyone... can you recalibrate these at the instrument? What does the button do?Jonathan Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted May 24, 2018 Member Share Posted May 24, 2018 My talents are limited to twisting the wheel and hooting the hooterReplacing the bits inside the drive is intricate. Are you planning to do it yourself?Jonathan Link to comment Share on other sites More sharing options...
JimmyRocks Posted May 24, 2018 Author Share Posted May 24, 2018 Absolutely not! (That is a Bertie Wooster quote, by the way. If you can conjure up an image of Bertie working on the intricate parts of a Caterham then that is the level of stupidity I would apply.)I have someone doing it for me, but need to source the bits. Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted May 24, 2018 Area Representative Share Posted May 24, 2018 If its the post 2005 speedo, it does not matter what speedo drive gears are fitted in the gearbox.I helped out a friend a couple of years ago. The gear that is pressed on the gearbox output shaft had come loose, so the speedo drive gear didn't have anything driving it. I made a bracket and mouted a proximity detector to detect diff input flange bolts. I did a little maths and wotked out the pulses/mile based on tyre size and diff ratio, and calibrated the speedo to suit. Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted May 24, 2018 Area Representative Share Posted May 24, 2018 Incidentally, why do you think you need to obtain a speedo drive gear? Link to comment Share on other sites More sharing options...
Area Representative Richard Price Posted May 24, 2018 Area Representative Share Posted May 24, 2018 So is it a given that I have a 3.92 diff? Unless your car was originally supplied with a six speed 'box (or a bike engine), you're unlikely to have anything other than a 3.92 diff. Link to comment Share on other sites More sharing options...
JimmyRocks Posted May 25, 2018 Author Share Posted May 25, 2018 Thanks everyone. That is a great help.It need replacing because the spindle of it has broken and will not engage with the drive sensor.The drive gear is the original that will have been in place when I initially had a cable driven speedo.Sounds as if the speedo can be recallibrated according to whichever drive gear I have, although adjusting the callibration seemed difficult when I first had the electronic speedo.Seems likely to be the 24 tooth gear then. And if not then the speedo may need recallibration. Link to comment Share on other sites More sharing options...
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