13 replies to this topic

[gooley]

My speedo is incorrect so I checked the speedo calculator to find the correct speedo driven gear for my trimatic....

http://codes.oldholden.com/Speedo/

 

and my LC is inaccurate by 19.54%.... at 100km/h my speedo reads 119.5km/h (Driven Gear - White 20 teeth)

 

So I choose a different driven gear to Yellow 24 teeth which is results are -1.08%,,,, at 100km/h my speedo reads 98.9km/h

 

Is it safe for me to go and just buy the yellow and fit it to my trimatic....Simply fit and off we go?

 

 

Well this is my details that I put into the calculator

Tyre Size - 205/60 R13

Diff Ratio: 3.36

Gearbox: Trimatic (M40)

Gearbox Drive Gear: White 8 Teeth (I'm assuming it's white)

 

Now I know that I do have the White 20 Teeth Driven gear fitted as I bought a new one 2 years ago and didn't even think about fixing the inaccurate speedo

Edited by gooley, 20 October 2013 - 08:24 PM.

[S pack]

The LJ parts catalogue lists:

24 tooth gear (yellow) for a 3.36:1 ratio diff.

20 tooth gear (white) for a 2.78:1 ratio diff.

[gooley]

Well there you go I guess one of the previous owners put in a different diff and didn't change the speedo gear or changed the speedo gear and just put a random one in.

 

So I'll just go ahead and order a yellow one from rare spares

[gooley]

But wouldn't you want -1.08% off instead?
but either way I'm not fussed because it would be better than 19% off.

Edited by gooley, 21 October 2013 - 07:40 AM.

[S pack]

walpolla

A red with 23 teeth would be the one:

@ 100 it reads 103.

 

 

Better to have your speedo reading slightly higher than your actual road speed.

[gooley]

Ok no worries. Thanks for that I will buy the red one

[gooley]

walpolla

A red with 23 teeth would be the one:

@ 100 it reads 103.

 

 

Better to have your speedo reading slightly higher than your actual road speed.

oops... I'm a bit confused lol... So which one should I buy??

 

(Because as you said the Yellow is for 3.36 Ratio and that's what I have)

Edited by gooley, 21 October 2013 - 04:46 PM.

[N/A-PWR]

Hi Jason,

Seems they are saying the red is better but Dr Terry say's 1 tooth per 5kmh out @ 100kmh,

So 120kph on the speedo @ 100kph actual is 20kph out divided by 5 = 4 teeth extra than what was used.

 

4 teeth extra + 20 tooth actual = 24 teeth needed

 

If you give me your rear tyre diametre, I can work it out another way. Dave I

Edited by TORYPOWER, 21 October 2013 - 05:02 PM.

[gooley]

Well these are my Tyre size - 205/60 R13.....cheers

 

or

 

22.7X8.1 R13
 

Edited by gooley, 21 October 2013 - 05:23 PM.

[N/A-PWR]

M40 will have to have a White 8 tooth driver gear which the calc's say's you do:-

 

3093 rpm @100 kph actual speed:-

 

Red     = 103.4 kph

Yellow =  98.9 kph

Edited by TORYPOWER, 21 October 2013 - 05:49 PM.

[gooley]

M40 will have to have a White 8 tooth driver gear which the calc's say's you do:-

 

3093 rpm @100 kph actual speed:-

 

Red     = 103.4 kph

Yellow =  98.9 kph

 

I'm just going to buy the Yellow one as its closer to 100kph. My Speedo will read 98.9kph and actual speed is 100.

 

It's better than what I got now with the speedo off by 19-20kph off

Edited by gooley, 21 October 2013 - 07:52 PM.

[gooley]

This is the calculator I use.

 

http://codes.oldholden.com/Speedo/

 

        regards,Rod

Did you see my original post.... It's the same link