Speedometer reads way too fast

[slovcan]

The tach error means you have a V6 cluster in a V8 truck lol. You can swap out the magneto for the fuel gauge by itself to make it less active again, as well as the odometer assembly. And yes, the magneto should be the same between the US/export models.

Hey, thanks Brandon. Yeah, I figured that was the case with the V6 vs V8 tach. I gather the magneto you refer to is the motor (or as I have seen here "air core motor") that drives the needles?

Do you think - and anyone else who has a thought - that replacing the magneto will restore my speedometer's accuracy? Somewhere along the journey I saw it written that the tachometer and speedometer use the same motor - well, not the same one, but two identical ones identified with an "S". If so, maybe swapping out a tach motor for my bad speedometer motor could resolve this? Of course the tach motor should be out of a V8, I guess...

Thanks,
Glenn

 

[east302]

Dorman does the rebuilds apparently, but I'm losing hope.

The reviews of those on Summit are pretty bad.

I’d try my hand at replacing the air core motors.

https://www.summitracing.com/parts/rnb-599-350#overview


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[AK49BWL]

Hey, thanks Brandon. Yeah, I figured that was the case with the V6 vs V8 tach. I gather the magneto you refer to is the motor (or as I have seen here "air core motor") that drives the needles?

Do you think - and anyone else who has a thought - that replacing the magneto will restore my speedometer's accuracy? Somewhere along the journey I saw it written that the tachometer and speedometer use the same motor - well, not the same one, but two identical ones identified with an "S". If so, maybe swapping out a tach motor for my bad speedometer motor could resolve this? Of course the tach motor should be out of a V8, I guess...

Thanks,
Glenn

The motors for the speedo and tach run off internal gauge electrics, so the motors for them (magneto, air core thing, yes lol) should actually be the same in ALL the clusters (of similar design), v6/v8 notwithstanding. You could give it a shot! Worst case, it just doesn't work. You're not likely to burn anything out trying at least.

 

[slovcan]

The reviews of those on Summit are pretty bad.

I’d try my hand at replacing the air core motors.

https://www.summitracing.com/parts/rnb-599-350#overview


Sent from my iPhone using Tapatalk

The motors for the speedo and tach run off internal gauge electrics, so the motors for them (magneto, air core thing, yes lol) should actually be the same in ALL the clusters (of similar design), v6/v8 notwithstanding. You could give it a shot! Worst case, it just doesn't work. You're not likely to burn anything out trying at least.

Hey, thanks guys. It looks like I have to try changing the motor on the speedometer. There are a couple on eBay, but postage is stupid high - especially with that eBay Global Shipping Program that steals our money for fictional import fees. Maybe I'll try to swap the tach motor out of the next cluster I get from the salvage yard if the speedometer one is buggered but the tach is accurate. Strange that the speedometer is the one that fails in all of them when the tach one does as much or more work.

Cheers,
Glenn

 

[slovcan]

Well folks, still struggling with this. I picked up another used cluster today. It looks better in that it only has 197,000 kms on it versus my 281,000 kms. The speedometer and tachometer needles don't fall at all or just a mm maybe when the cluster is held inverted. BUT, this one's tachometer only goes to 5000 with a 4000 redline versus mine which is 6000 with no redline. Also, this new one's speedometer only goes to 160 km/h (100 mph) where mine is 180 km/h.

So, a couple of questions - what year/model would that be out of and would the speedometer/tachometer motors be the same "S" motors like mine has? If this cluster's speedometer is accurate I'll try swapping the motor over to my speedometer.

Thanks you,
Glenn

 

[slovcan]

Well folks, still struggling with this. I picked up another used cluster today. It looks better in that it only has 197,000 kms on it versus my 281,000 kms. The speedometer and tachometer needles don't fall at all or just a mm maybe when the cluster is held inverted. BUT, this one's tachometer only goes to 5000 with a 4000 redline versus mine which is 6000 with no redline. Also, this new one's speedometer only goes to 160 km/h (100 mph) where mine is 180 km/h.

So, a couple of questions - what year/model would that be out of and would the speedometer/tachometer motors be the same "S" motors like mine has? If this cluster's speedometer is accurate I'll try swapping the motor over to my speedometer.

Thanks you,
Glenn

UPDATE:

Well, I tried that cluster. With a redline starting at 4000 and only going to 5000, I suspect it is out of a diesel, even though the gas gauge doesn't say Diesel Fuel Only. The speedometer is about 6 or 7 km/h high at 80-90 km/h and maybe 8 km/h high at 100 km/h.

Today I moved the speedometer motor over from the replacement cluster to my original. The speed error is the same as I noted with that cluster which means the fault is with my original motor and not the electrics in the cluster itself. The error with the lower mileage motor is: dead accurate up to 55 km/h, reads 63 km/r at actual 60, reads 75 km/h at 70, 86 at 80. In other words, my old one was 25-30% high at speeds up to 40-50 km/h and 17.5% high at 100 km/h. This one's maximum error is 7 or 8%.

Now, here's where it gets interesting. Both the speedometer and tachometer are "S" motors with the speedometer marked "S 1F" and the tachometer marked "S 1E". Apparently these motors can be interchanged. I think this might be a great idea because the tachometer spends most of its life at a needle position less than half of the speedometer needle position, relatively speaking. This could mean the tachometer motor works less than half as hard as the speedometer motor. It's always the speedometer that reads high, never the tach.

I tried this today and I really think it will work. Someday I may try it. The only thing that needs to be done is to trim off two little plastic locating tabs (about 2mm each) so the tach motor can be put in the speedometer location.

Cheers,
Glenn

 

[east302]

BUT, this one's tachometer only goes to 5000 with a 4000 redline versus mine which is 6000 with no redline.

The 95 (TBI) had the 5,000-rpm tach. 96 and up had the 6,000.


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[slovcan]

The 95 (TBI) had the 5,000-rpm tach. 96 and up had the 6,000.


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Ahh, OK then. Not from a diesel.

So I did cut those two locating tabs off the bad speedometer motor this afternoon and mounted it on the tach location on my "spare" cluster. So, that will also work to mount a tach motor for the speedometer. When I get tired of having even the smaller error, I'll put the tach motor in and see what happens.