Speedo driven gears

Driveline (including transmissions, differentials, tailshafts) discussion.

Speedo driven gears

by coxy64 [old] » Tue Dec 20, 2011 9:09 am

I know you can change the driven gear for holden boxes to correct your speedo, but what about jap 4/5 speed is the same possible,if not, how do you rectify it anyone now?? Coxy.
 
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Re: Speedo driven gears

by utility8 » Tue Dec 20, 2011 2:01 pm

I would assume that there would be a variety of driven gear options Coxy.
If there isn't, you can get a ratio box made to correct any speedo error.
The ratio box fits to you box then the speedo cable screws into it.
To determine the error, a counter is fitted to your speedo cable & the car is taken over a measured mile.
An EH speedo requires 1000 revs per mile.
Whatever yours is, let's say 900 revs, a gear set for the ratio box is calculated to increase the revs by 100 to 1000.
The box is about the size of a match box. I have one fitted to my ute.
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Re: Speedo driven gears

by coxy64 [old] » Thu Dec 22, 2011 8:33 am

Thanks John will look into it some more, switching to 3.55-1 ratio i though with all the jap box conversions done to members cars someone would have sorted this problem all ready. Must be a lot of inaccurate speedo's out there. Coxy
 
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