rayjackson1950 Posted September 23, 2022 Share Posted September 23, 2022 Can I check the diff ratio without removing the diff.I assume I can when in the air by counting wheel turns against prop turns, but all I have found is how to do it with the diff removed.I'm interested as the speedo against Google maps suggests the speedo is about 10% out. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted September 23, 2022 Member Share Posted September 23, 2022 Yes.Jack up one rear wheel and leave the other on the ground with the brakes OFF and the wheel chocked. (Corrected, see below.) Put the gearbox in neutral. Mark both the prop shaft and the rear wheel to make it easier to count turns. Turn the lifted wheel 10 times (other options are available) and count the turns of the prop shaft. Divide that number by ten because you've turned the wheel ten times (or whatever) and then by two because you've only been turning one wheel.Or something like that.Jonathan Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted September 23, 2022 Member Share Posted September 23, 2022 "I'm interested as the speedo against Google maps suggests the speedo is about 10% out."That's the instantaneous speed display on a smart 'phone rather than some distance over time calculation?Jonathan Link to comment Share on other sites More sharing options...
simon_h Posted September 23, 2022 Share Posted September 23, 2022 Speed reading 10% high or low? High is correct and within tolerance so you are more likely to be within the speed limits. Low needs addressing. Link to comment Share on other sites More sharing options...
John Vine Posted September 26, 2022 Share Posted September 26, 2022 #2:...with the brake on...I think that should read "off", JK?JV Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted September 26, 2022 Member Share Posted September 26, 2022 I knew that something was wrong! Thanks for the correction.Brake OFF, wheels chocked.Jonathan Link to comment Share on other sites More sharing options...
Youds7 Posted October 1, 2022 Share Posted October 1, 2022 The ratio is stamped on my diff. Link to comment Share on other sites More sharing options...
Leadership Team SLR No.77 Posted October 1, 2022 Leadership Team Share Posted October 1, 2022 The ratio is stamped and written in felt tip on my diff, 3.62, but I'm convinced from rpm/mph readings it's a 3.92. On the list of things to investigate this winter. Link to comment Share on other sites More sharing options...
rayjackson1950 Posted October 9, 2022 Author Share Posted October 9, 2022 Hi GuysThanks for the info. I have now checked and get 16 turns of the wheel to 33 turns of the prop.I make that 1.03.It was originally a race care so I wouldn't be surprised to have a lower ratio diff. But 1.03 doesn't sound right to me. I did look up some blurb donkeys ago and thought the lowest Ital diff was 3.77.The question is, have I made a schoolboy error? Or is it correct. As a matter of interest I can easily accelerate from 35mph in 5th gear. Another reason I thought I hade a low ration diff.Any thoughts, or polite abuse if I have made a stupid error, would be appreciated. Link to comment Share on other sites More sharing options...
Member Jonathan Kay Posted October 9, 2022 Member Share Posted October 9, 2022 Did I mean multiply x 2?Jonathan Link to comment Share on other sites More sharing options...
John Vine Posted October 9, 2022 Share Posted October 9, 2022 Re #10:You did, JK.16 wheel turns for 33 prop turns gives a final drive ratio of ((33/16) x 2) = 4.125 (certainly very low-geared).JV Link to comment Share on other sites More sharing options...
7 wonders of the world Posted October 9, 2022 Share Posted October 9, 2022 You have blatmail Link to comment Share on other sites More sharing options...
rayjackson1950 Posted November 3, 2022 Author Share Posted November 3, 2022 Thanks all for the info guys. I now need to find a higher ratio diff. I think I read in the build manual, or somewhere similar, that they do 3 different ratios, being4.1253.993.77Or there abouts Link to comment Share on other sites More sharing options...
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