Speedometer reads way too fast

[slovcan]

Mine is reading 35 at 30mph,47 at 40,58 at 50,70 at 60 and 82 at 70. 103000 miles-had smaller wheels(diameter) for a while-I don't know how long. Changing wheels to about regular diameter made no difference whatsoever. I drove for a while with gps on until I memorised these numbers.

Even though yours is miles and mine is km's, the error in both of ours is virtually identical at 17-17.5%.

 

[slovcan]

Here’s a link that should help with the odometer:

https://www.gmt400.com/threads/changing-mileage-odometer-cluster-swap.46145/

Per GM, a speedometer reading within 4-mph of a GPS was within spec.


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Thank you east302. That is exactly what I needed to go along with the video. I should be able to get this done.

 

[Erin]

Hi folks,

OK, about these clusters with the speedometers reading way higher than they should. I have determined that my speed sensor and odometer match my GPS (speed via the OBDII port). That seems to be the "they all do that, sir" problem of the speedometer itself. It also seems the solution is to replace the cluster.

So, question 1) At what mileage does this problem generally rear its ugly head? Mine was doing it when I get it at 239,000 kms (148,500 miles). It hasn't changed in the past 41,000 kms. I have a replacement on the way with 144,000 kms on it (89,500 miles). No returns allowed.

Question 2) What are my odds that this will be a good one?

Question 3) Is there a how-to somewhere that I can follow to move my odometer over from my current cluster to the replacement?

Thanks all,
Glenn

If you’re able, there is a place in Washington you can send your cluster to and they will repair it. My uncle had same problem and it cost him $189.

 

[slovcan]

If you’re able, there is a place in Washington you can send your cluster to and they will repair it. My uncle had same problem and it cost him $189.

Thanks Erin. Could you ask your Uncle for the name of the place for me? Maybe I can ask them if they'll do a core sort of exchange or something. I can't really do without it for a month or more.

I wanted to just replace it with a good used one, but they are as rare as hens' teeth up here. I thought I found one and the local salvage yard brought it in for me only to find it had 340,000 kms on it instead of the advertised 144,000 kms. MPH clusters are a dime a dozen, but no Km/h ones.

By extension, does anyone know of a DIY repair I can do? Can I maybe change the speedometer drive motor?

Thanks,
Glenn

 

[Erin]

Thanks Erin. Could you ask your Uncle for the name of the place for me? Maybe I can ask them if they'll do a core sort of exchange or something. I can't really do without it for a month or more.

I wanted to just replace it with a good used one, but they are as rare as hens' teeth up here. I thought I found one and the local salvage yard brought it in for me only to find it had 340,000 kms on it instead of the advertised 144,000 kms. MPH clusters are a dime a dozen, but no Km/h ones.

By extension, does anyone know of a DIY repair I can do? Can I maybe change the speedometer drive motor?

Thanks,
Glenn

Issautomotive. Said he got it back in 4 days. I don’t know any DIY fixes.

 

[slovcan]

Thanks Erik. Much appreciated.

 

[east302]

It looks like there are a few links in this video for the air core motors. Maybe it will help.

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[slovcan]

It looks like there are a few links in this video for the air core motors. Maybe it will help.

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Thanks east302. I'll get in touch with them, too. I have to try to find out if it is the motor or the circuit board that causes the optimistic speedometer. Changing out the motor looks simple enough. The circuit board would likely require better soldering skills than mine.

 

[slovcan]

Hi folks,

Well, I'm batting zero. The cluster I had ordered turned out to be junk so the salvage yard called to say it was a no-go.

Then I found another yard that wasn't part of the national network. He has a bunch of these trucks. The first cluster I got from him had 471,000 kms on it. The speedometer error was the same as my original and the gas gauge was way more active than mine. He exchanged that for a lower km one (20,000 kms less) and it also had the same speedometer error as my original. The tach, though, read about 300 high at idle, 1500 high at highway speed and hit 6,000 RPM at 3/4 throttle automatic shifts. AND, it was out of a manual transmission truck. All the needles on that one were much better damped than mine, though.

So, he is getting me another one to try this week. If that doesn't work out he'll refund the money. It's refreshing to find someone who bends over backwards to help AND will refund electrical parts. Old school, in his 70's and his own private yard.

I tried emailing everyone in the links and who you guys recommended. I didn't get a single answer. Maybe because I'm in Canada, who knows. CarID used to sell rebuilt clusters, but don't have any now and aren't likely to have any, let alone in kms. I can't find them on Rock Auto like someone said they were. Dorman does the rebuilds apparently, but I'm losing hope. I guess that leaves trying to find one of those motors for the speedometer. Does anyone know if the motors are the same on the km/h and mph ones?

Thanks,
Glenn

 

[AK49BWL]

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.