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Spitfire FK box with J-type overdrive - missing speedo drive parts?


Colin Lindsay
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I've been given a Spitfire FK gearbox (US-spec 1300?) with J-type overdrive and am intending an overdrive conversion into the Herald 13/60 but am missing parts from around the speedo drive.

I have an angle drive already, I know there's a bracket and a bolt missing but what does the bracket hold in place? I can't find a good diagram and my Workshop Manual only covers D-type.

IMG_0456.thumb.jpg.95c5db3991b7ae92a7e45c4d52aa2f22.jpg

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23 hours ago, Pete Lewis said:

Pete - any idea if the speedo drives need to be swapped over? I think mine is damaged at the end, so may as well replace it. It's an 18 tooth so from a US-spec Spitfire box. Were the gauges similarly adjusted for the US market, so if I fit a US drive with a cable to a UK speedo will it affect the accuracy? Would the drive gear on the output shaft need to be changed too, as any other number of teeth might not mesh?

Here are the available options:

373333063_ScreenShot2021-09-22at20_09_42.png.9743b4a4c603a59fc08032e994e1bee9.png

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5 hours ago, Peter Truman said:

For what it is worth an analysis I did a while ago trying to determine what speedo drive (No of teeth) to fit with Spit 1500 single rail internals into a 3 rail box with J type O/D with a std 4:11 diff.

Oops how do I upload a Microsoft Excel spreadsheet?

Take a screenshot, pop that into "Paint" then post that as an image?

Not everybody has MS office....

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Not having a good day inserted the tables into the Spotted section so I've deleted it and will start again, Bu**er!

Please let me know if there's any errors, & I must revisit and work out the best speedo gear for a Spit 1500 engine and single rail 1500 gearbox gears (fitted into a 3 rail case) with a J Type Overdrive mated into a Spit Mk2 with a std 4:11 diff, and speedo head.

Peter T

Speedo Drives Pg1.jpg

Speedo Drives Pg2.jpg

Speedo Drives Pg3.jpg

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That hurt my neck, turning my head sideways so I just turned the monitor sideways and hurt my arms instead, before deciding that it was easier to just rotate the image. :)

 

Interesting to note that if my box is FK, so Spitfire Mkiv for the US market, it has a blue 18 tooth drive; the one listed below appears to be blue 24 tooth? The 18s are all brown?

411009336_SpeedoDrivesPg2.thumb.jpg.23cf6f20a8037691ad2acfb4d9d46fde.jpg.638a6438e04269faa2a3df1ec9453c12.jpg

697072758_SpeedoDrivesPg3.thumb.jpg.5c611fcdfdc0ade210c779c319bd3fc2.jpg.a9bdf8d8d59830c036b37bbe42f2ef4d.jpg

847508761_SpeedoDrivesPg1.thumb.jpg.60975275a1da9f345656971b95c53578.jpg.72dc67ddd68f9d95f7ee9b081f2b3045.jpg

 

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at least its easy to swap pinons 

you can calc the TPM    if the car is mobile  mark road  and tyre , stick a card pointer on the speedo cable or its drive

push car exactly 52.8ft count the needle turns     divide 5280 by the turns and thats the TPM  you  are trying to match

if the car is not mobile you need to dived 52.8ft by the rolling circumference of the tyre  then turn the wheels exactly that amount 

which might be easier than pushing the car !!!

sorry  i only work in ft and ins.

Pete

 

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