29 replies to this topic

[Bigfella237]

A 10yo thread resurrection, well done!

 

We would need to know your exact rear tyre size to work out the revolutions per km, if you give me that then I'll crunch the numbers and figure out which speedo gears should get you close?

 

By the sounds of it you may need to pull the extension housing of the trans and change the driven gear too?

[kiwi-lilj]

What happened to chopper ?

[gtrboyy]

Thread dig aye...haha

 

Tim the gears ol' chop chop posted about are for trimatic or m20 gearbox not for th350...no biggie.

 

google 'speedo gear calculator th350'

 

You'll need to know actual wheel diameter & both drive/driven gears then can work out which ones needed to correct speedo.

[rodomo]

He didn't get banned......he just dropped off the radar.................personal issues and the like.

[Uncle Chop Chop]

I know John (chopper) from the mens shed. Its been 11 years since that car crash. Despite what all the doctors reports said, he is on the mend.

[N/A-PWR]

Never knew that Vick,

 

 great news.

 

I know John (chopper) from the mens shed. Its been 11 years since that car crash. Despite what all the doctors reports said, he is on the mend.

Like button for you

[Bigfella237]

i have 215/ 50/ 13 and it worked out to around 545 and I could not find that, as  am also running A W50 toyota box with 3.08 diff

 

Ivan, I entered your tyre size (215/50R13) into my calculator and I get 583 revolutions per kilometre (if that's what you're asking)?

 

I have no idea what speedo gears come in a W50 or where you would get different sized gears, but you should still be able to count the teeth... these are the closest I come to accurate with your tyre size and diff ratio:

 

If your drive gear is 7 teeth then the driven should be 20 teeth (speedo reads 100.5km/h @ 100)

If your drive gear is 8 teeth then the driven should be 23 teeth (speedo reads 99.9km/h @ 100)

 

Although with a Toyota box you might be better off looking at one of those speedo adapters that go into the cable?

[Uncle Chop Chop]

I think the Toyota boxes have more like 30 teeth on the driven gear, but don't quote me.

[Bigfella237]

Okay, as you can see the speedo drive ratio is around 2.875 to 1 for that particular tyre/diff combo, so if you have a 30 tooth driven gear then you need a 10 tooth drive gear (it actually comes out to 10.435 teeth so maybe an 11 tooth gear would do)?

[Bigfella237]

I've got 205/60 R13's, 3:55 ratio diff, off a M20 box.. car is an LJ, red 6..

On the highway I'm doing around 3,000 rpm and the speedo's showing I'm doing around 130kph PLUS when I'm actually doing somewhere just above 100kph..

 

G'day Ian (sorry, I thought we were shortening names here now),

 

It will depend on which drive gear is inside the gearbox, if you remove the speedo cable and look inside the hole you should be able to identify the colour of the drive gear on the output shaft. You may even need to change this drive gear depending on whether you can find an appropriate driven gear?

 

If you have the red 7 tooth drive gear, the closest I come is the dark blue 22 tooth driven gear, which should read 99.7km/h @ 100

 

Or if you have the white 8 tooth drive gear, the closest I come to is the light blue 25 tooth driven gear, which should read 100.3km/h @ 100

 

None of the other drive gears even get close with such a low diff ratio. Looks like the red drive gear is not available from Rare Spares but the white one is, along with a variety of driven gears... see here:

 

http://www.rarespare...OMPONENTS&pno=3

 

If your speedo is currently reading 130km/h @ 100 then I'd guess you either have a white drive gear with a pink driven gear, or a blue drive gear with either a dark blue or green driven gear?

 

EDIT: My gear ratio calculator says that with your tyre size, in fourth gear, a 3.55:1 diff should be doing 3,266 RPM @ 100km/h

 

A 3.36:1 diff ratio would be doing 3,091 RPM @ 100km/h

 

Tyre Size = 205/60R13
Tyre Revolutions = 552 per km
Gear Ratio = 1.00 : 1
Diff Ratio 2.60 : 1 = 2392 RPM @ 100km/h
Diff Ratio 2.78 : 1 = 2558 RPM @ 100km/h
Diff Ratio 3.08 : 1 = 2834 RPM @ 100km/h
Diff Ratio 3.36 : 1 = 3091 RPM @ 100km/h
Diff Ratio 3.55 : 1 = 3266 RPM @ 100km/h
Diff Ratio 3.70 : 1 = 3404 RPM @ 100km/h
Diff Ratio 3.90 : 1 = 3588 RPM @ 100km/h
Diff Ratio 4.11 : 1 = 3781 RPM @ 100km/h

Edited by Bigfella237, 29 November 2016 - 07:59 PM.

[Bigfella237]

Bloody hell, ran out of "edit time" again...

 

Just for interest sake, your shift points for that combo (at 5000 RPM) should be:

 

 

Tyre Size = 205/60R13
Tyre Revolutions = 552 per km
Diff Ratio = 3.55 : 1
5000 RPM in 1st Gear (3.05 : 1) = 50 km/h
5000 RPM in 2nd Gear (2.19 : 1) = 70 km/h
5000 RPM in 3rd Gear (1.51 : 1) = 101 km/h
5000 RPM in 4th Gear (1.00 : 1) = 153 km/h
5000 RPM in Rev Gear (3.05 : 1) = 50 km/h

 

Edited by Bigfella237, 29 November 2016 - 08:12 PM.

[N/A-PWR]

Go to a 5 km roadside marker 'Start and Finish',

 

 look at the speedo distance reading,

 

 do the 5 K, and re-check speedo distance reading.

 

 

If you have Miles, 5 K is 3.1 Miles

or the calc is 5000 divided by 1.6 = 3.125

 

 

 

 

When the correct gears are in,

 

 the distance reading is right, and the speedo speed reading is right.

 

 

Then if everyone is overtaking you, the speedo speed reading is wornout!

Edited by N/A-PWR, 29 November 2016 - 09:45 PM.

[Bigfella237]

looking at the gear shift chart I'm thinking that my box may be an M21 as I'm sure I get more speed out of 1st & 2nd then what the computer says

 

Are you absolutely sure you've got a 3.55 diff and not a 3.36?