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I was checking my speedometer with a gps, and noticed it reads about 25% low when going about 25mph, but is much closer to the gps when going 50mph or above. The gps pretty much matches my car's speedometer within a couple mph at all speeds.

I'm pretty new to this vehicle, so was wondering if others had seen this kind of behavior. It's an Austrian 712 with a 120kph speedometer in it.

Thanks
Scott

Generally, the Pinz speedos read high. Many have a right-angle adapter under the speedo that (I think) made them read several percent higher; I'll assume this was to help keep speeds reasonable even if the operators "thought" they were flying fast.

But the inconsistency that you see between low and high speeds would suggest that the speedo has some real problem. It may only be due to stiff lube after decades or something more serious. I'd suggest just replacing it with a good electronic speedo and be done with the problem.

Hi Jim, thanks for the reply. If there a lube point for this that I can try? Just some additional info. I'm using stock tire sizes 235/85/16. It also occurred to me that when I get the higher error at lower speeds, I'm in 4th gear and when it reads closer to the correct speed, I'm in 5th gear. Not sure if that would matter. This is one of the Austrian trucks that went back to Graz in the late 90s, and as far as I know, has not had any modifications made to the driveline since leaving service.

I may just end up replacing the speedometer as you suggest and be done with it.