Ratty43 Posted March 28, 2014 Share Posted March 28, 2014 As per the topic really, during my recent clutch change I stupidly trapped the speedo cable between the bell housing and the engine (R380 & 300tdi). That resulted in the socket end of the speedo drive shearing (amazed it was the plastic gear that went). That didn't bother me too much as it's always read 10% over the actual speed so I had been intending to change it for a more accurate reading. With that in mind I bought a 20 tooth drive to replace the 22 tooth one that was in there thinking it would spin 10% faster correcting the speedo. Went out with the sat nav today and it now reads 20% over. Does this mean I've been daft (certainly seems so!) And need a 24 tooth drive instead? Thanks in advance. Quote Link to comment Share on other sites More sharing options...
Ex Member Posted March 28, 2014 Share Posted March 28, 2014 Personally...I would buy a VDO speedo. They look better, you can see them at night and you can program them to be correct. So... read what you wrote above. "...it's always read 10% over the actual speed..." then "... thinking it would spin 10% faster..." You seem to understand you purposely chose a gear to make the speedo spin faster, but you wanted it to spin slower in order to correct the speedo error. So, yes, more teeth equals speedo runs slower. Quote Link to comment Share on other sites More sharing options...
Ratty43 Posted March 28, 2014 Author Share Posted March 28, 2014 Bloody hell. I can't for the life of me see how I managed to be quite that thick. I'm off to sit in the corner. Cheers for that, it was one of those wood for the trees moments where I bought it knackered and the idea stuck. Quote Link to comment Share on other sites More sharing options...
Ex Member Posted March 28, 2014 Share Posted March 28, 2014 Happens to me all the time. Quote Link to comment Share on other sites More sharing options...
Ratty43 Posted March 28, 2014 Author Share Posted March 28, 2014 Same here. 24 tooth drive on order and that should see it spot on. Hopefully sell the 20t one to keep my Mrs happy...ish. Thanks for your help. Quote Link to comment Share on other sites More sharing options...
Mr Noisy Posted March 28, 2014 Share Posted March 28, 2014 20t units are popular, many people buy them after fitting big tyres, myself for example However now fitting different ratio diffs and changing the transfer case ratio AGAIN it's time for another rethink! Quote Link to comment Share on other sites More sharing options...
discomikey Posted March 29, 2014 Share Posted March 29, 2014 my speedo seems to have an affliction to lasting any length of time, although being a series xfer box and taller tyres and a 3.54 diff it pretty much reads in KPH what youre actually travelling in MPH lol ive never found evidence of correction for series speedo's though unfortunately Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted March 29, 2014 Share Posted March 29, 2014 Mr Noisy, transfer box ratio won't make an iota of difference, as it reads the propshaft speed Diff and tyres obviously will Quote Link to comment Share on other sites More sharing options...
Mr Noisy Posted March 29, 2014 Share Posted March 29, 2014 Mr Noisy, transfer box ratio won't make an iota of difference, as it reads the propshaft speed Diff and tyres obviously will yeah sorry dude, thanks for clarification, it was more explaining the fact that i have changed the diffs and the transfer ratio, to end up with the same overall ratio in high range but a different propshaft rpm for given road speed thus will need to mess about with speedo gears again Quote Link to comment Share on other sites More sharing options...
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