13 replies to this topic

[N/A-PWR]

Ryan,

 

You need a Trimatic ( M40 ) driven Gear of, Yellow 10 Tooth,

 

and a Speedo Cable Follower Gear, of Dark Blue 22 tooth.

 

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

 

Which would get you 98.8kph ( Speedo Reading ) at 100kph actual.

Hey guys running 225/60/15 tire with 3.7 gears and trimatic , which teeth speedo gear will I need ?

Edited by GASPOWER, 03 August 2014 - 07:30 PM.

[N/A-PWR]

I stuffed that one Up Sorry Ryan,

 

Hit the wrong Diff ( 2.78 ),

 

Was going to say that the White Driver is probably what is already in the Box,

 

and was going to make an adjustment so you could leave the White in,

 

but now discovered the Error.

 

So starting again, using White as the Driver Gear:-

 

- 3.55 Diff x Dark Blue 22 tooth = 101 kph

 

- 3.89 Diff x Yellow 24 tooth = 101.5 kph

 

so the 3.7 Diff is in between:-

 

- 3.7 Diff x Red 23 tooth = 100

 

Thanks heaps gas power

[N/A-PWR]

Hi Ryan,

 

Leaving the Blue Driver in,

 

So starting again, using Blue as the Driver Gear:-

 

- 3.7 Diff x Light Blue 25 tooth ( speedo follower gear ) = 104.5kph speedo reading at 100kph actual speed

 

 

so it would be best to have the White as a Driver and the Red as the Speedo cable gear ( follower ), because there is no 26 tooth follower gear.

I checked the box and its a blue gear drive inside so what speedo color do I now need ?

[arrimar]

As an aside, the blue shaft mounted drive that rare spares sells is nothing like the original blue in colour. What may appear opaque white in an old box may really be the old blue.

[N/A-PWR]

Great point Arrimar,

 

Now as I am a Machinist, when we do multiple threads, they are called 'Thread Starts',

 

so when you look from One Side of the Speedo Drive Gear in the Picture below,

 

you can count the 'Thread Starts' going around in one 360 degree count,

 

now that Blue one there has 9 starts, if it were the White gear, there would only be 8 starts:-

 

Click on an image for a bigger size.

                              https://www.rarespar...1000&brand=RARE

https://www.rarespar...1001&brand=RARE

 

 

 

 

As an aside, the blue shaft mounted drive that rare spares sells is nothing like the original blue in colour. What may appear opaque white in an old box may really be the old blue.

Edited by GASPOWER, 05 August 2014 - 02:54 PM.

[N/A-PWR]

These Types of Speedo Drive Gears/gears are also known as a 'Worm Gear',

 

( A normal Bolt, has a One Start thread, which means, One Turn of the Bolt = one pitch of the thread Traveled )

 

(( A multiple start thread ( say a 9 start ), would travel 9 pitches of the thread in one Turn ))

 

A Pitch of a Thread, is the distance between each tooth:-

 

 

So this brings us to 'Pitch Gauges':-

 

If we knew the pitch of the Blue and White Worm Gears,

 

we could use a Pitch Gauge to Test.

Has anyone got a Trimatic ( M40 ) Blue and a White Speedo Drive Worm Gears to Measure with their Pitch Gauge Set?

Edited by GASPOWER, 05 August 2014 - 03:24 PM.