[Gwagensteve]

OK brains trust, I need a hand here with a question on our club FB page.

Owner is complaining his SJ50 with 205/70/15 tyres has a very inaccurate speedo - 100km on the speedo is 84km/h road speed.

Axle ratio is stock - 3.9.

I have crunched some numbers and I think I can confirm that 15" rim 1.0 and NT 1.3 15" rim will use the same speedo drive ratio. (~2% difference)

However, 6.00 X 16 variants have about an 11% taller tyre, so they must use a different speedo gear -AFAIK all the speedo gauges have the same calibration

I can see 12 and 19 tooth speedo gears advertised on line, but the application guides are no help at all, with everything fitting everything apparently.

Can anyone confirm if there are different part numbers based on tyre diameter/variant?

The FSM is no help to me as it doesn't list part #

[sideways]

It depends on the year but SJ40 or earlier SJ50 will have an FR78 tyre as standard which is 27.8".

Speedos can say whatever they like, especially after 30+ years. It's possible to adjust the spring tension or move the needle and make them say anything. He needs to check the accuracy of the odometer to see that speedo drive is correct. For example, the speedo in my old Land Rover is 20% out but the odometer is only 5% out. The speedo drive is correct but I'd say the clock spring has lost its tension.

[Gwagensteve]

Both relevant points, but the difference between an FR78 and a 205/70/15 is only 5%, but a 6.00 X 16 is 28.8", almost exactly the difference the OP is seeing.

Good point on odometer though.

[pete_79]

Can confirm that coily speedo gears are totally different to normal Sierras, but can’t comment on the specific models you’re asking about.
Makes sense that there should be different number of teeth on the factory fitted 16” variants.

[Beery]

I'll just put this out there. I have a transfer in bits that I was told was out of a tray back, so a 16" variant. I can't confirm 100% but the guy I got it off knows Suzuki's, although he did have a few cases there, so it could have been mixed up.

Anyway, it has a 20 tooth speedo gear.

I busted my speedo cable again (SWB 15") on the weekend too. I'll pull the gear out and compare when I change it if you don't come up with an answer by then.

[Gwagensteve]

I’ve seen 19 and 12 advertised but not 20.

Interesting.

[Beery]

you made me go count again but yes, definitely 20.

There's a few advertised on eBay and other sites. I searched samurai instead of sierra:

https://www.ebay.com/itm/134412167095

[Beery]

I also won't need to pull my speedo gear out. I just found this photo in my build thread:



You can see the gear perched up in the egg carton. It's certainly not 12 teeth. It's 20 as well judging from my zoomed in 1080p screen. I'm not sure what this means, maybe the other case I have Isn't from a tray back. My SWB is the weird 88.5 crossover model, so maybe something going on there.

[Brenno]

I have definitely pulled two different ones out of cases I've had. They are long gone but they were similar in tooth just a smidge different. I assumed it was because of the WT/NT diff gear differences?

[TASSIETOYUKI]

Bit of a grave dig, but did you work out what was going on with the vehicle in question?
My Baleno electronic speedo conversions odometer is reading about 10-11% lower/slower than actual and I have a theory why.

Interested to know what the outcome was from the mentioned reading faster.

[Gwagensteve]

No, I wasn’t able to add anything so as far as I am aware this is still unresolved.

[Blkfxx]

TASSIETOYUKI wrote:

Bit of a grave dig, but did you work out what was going on with the vehicle in question?
My Baleno electronic speedo conversions odometer is reading about 10-11% lower/slower than actual and I have a theory why.

Interested to know what the outcome was from the mentioned reading faster.

I recently put my other cluster in, with a baleno speedo and yellow box for speedo correction. Ive had the speedo reading correctly but odo was out (20km on the odo, 15km actual), Ive adjusted the ratio to fix the odo but then speedo is now out quite bit and doesn't have the same resolution. Not that this helps anyone, just thought I'd mention it

[TASSIETOYUKI]

Blkfxx wrote:

TASSIETOYUKI wrote:

Bit of a grave dig, but did you work out what was going on with the vehicle in question?
My Baleno electronic speedo conversions odometer is reading about 10-11% lower/slower than actual and I have a theory why.

Interested to know what the outcome was from the mentioned reading faster.

I recently put my other cluster in, with a baleno speedo and yellow box for speedo correction. Ive had the speedo reading correctly but odo was out (20km on the odo, 15km actual), Ive adjusted the ratio to fix the odo but then speedo is now out quite bit and doesn't have the same resolution. Not that this helps anyone, just thought I'd mention it

Hmm.. Very interesting. I need to do more digging and maybe grow a few more fingers to help with my math..

[TASSIETOYUKI]

My research has located 3 possible different speedo gear sets in switched transfer cases.

4x12 = 3:1
7x20 = 2.85:1
7x19 = 2.71:1

That is a 5% difference in each step.

Megazip suggests that,
4x12 were used on late 1.0 Sierra and MG410 narrow track?
7x20 were used on some 1.3 narrow track, 1.3 wide track and MG410 wide track?
7x19 were used on some 1.3 narrow track

[Gwagensteve]

Excellent work!

[sideways]

TASSIETOYUKI wrote:

My research has located 3 possible different speedo gear sets in switched transfer cases.

4x12 = 3:1
7x20 = 2.85:1
7x19 = 2.71:1

That is a 5% difference in each step.

Megazip suggests that,
4x12 were used on late 1.0 Sierra and MG410 narrow track?
7x20 were used on some 1.3 narrow track, 1.3 wide track and MG410 wide track?
7x19 were used on some 1.3 narrow track

Nice work!

[TASSIETOYUKI]

I have confirmed that my 1990 MG410 narrow track has transfer has 4x12