FJ Holden speedo drive gear

[ACT59FC]

If anyone out there has an FJ holden speedo drive gear they are willing to sell Id be really happy to hear from you. Just upgraded my FC diff from a 3.89 to a 3.55 and the FJ speedo gear will bring my speedo back to reading correctly.


Regards Rod.

[Errol62]

See my other post rod. I suggest you check your speedo before swapping gears. If FCRB26 is right your speedo should be okay as is.

Cheers
Clay


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[ACT59FC]

Hi Clay just checked out the old girl and it would appear that I do need that speedo gear. Its reading 5mph faster than actual speed. So when it reads 60mph on the speedo its showing 55mph on the Garmin. If anyone out there has an FJ speedo drive for sale. Id be real happy to hear from you.

Regards Rod.

[DCE80]

I have two crashboxes for spares. I'll check them but won't get a chance till late next week. I can't remember casting dates on them so unsure if they were fj fc fe. If you do Facebook jump on the grey motor enthusiasts page. They seem to be a helpful bunch and I'd be amazed if they couldn't hook you up with the goods immediately. See plenty of FJ pic's on there.
Dan

[ACT59FC]

Thanks Dan, much appreciated.

Rod.

[Errol62]

Very good. You appear to have effectively a 9% overdrive on factory spec assuming the speedo was originally correct. This is unlikely. As I said earlier most modern car speedos read fast by 2 - 7% ex-factory.

Your final drive is then perhaps slightly over driven with the smaller tyre rolling diameter and 3:55 diff. The 3:55 equates to an effective 10% overdrive over 3:89 with the smaller tyres negating this somewhat.

I don't know much about crash box speedo drives but in the later boxes the gear has around 20 teeth. So one less tooth provides a 5% decrease in speedo reading. Two less tree and you would be very close. Perhaps dangerously so in terms of getting clocked slightly over.

Cheers
Clay


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[Fraze]

I have a 3.55 diff in my FC and am running 185 x 13tyres. On advice from this forum I fitted an FJ speedo driven gear (23 tooth against the std 22 tooth) and this has corrected my speedo. At an indicated 60 mph the Garmin tells me I am doing 98 kph and that's near enough for me. Cheers Fraze

[Errol62]

Sorry but should have said one more tooth rather than one less in my last post.

98kph is 61mph. So you are actually going slightly faster than your speedo says.


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[DCE80]

You're in luck Rod I have two 23 tooth speedo drives. One for me and one for you.  Gearboxes were exposed to the elements before I ended up with them. I have wd40 soaked overnight and they have come up well and turn smoothly. I'd recommend flushing with solvent best you can and soaking in oil to finish off. Looks like only way to disassemble is to press gear off shaft then press back on while still maintaining end float in the assembly. I don't think that needs to be done though if you soak and clean a couple of times. The gear has part number 7409427 stamped on reverse side. It yours for postage cost. PM me details and I'll get it in the mail.
Dan