Speedometer Noise and sketchy readings

[Jason LeBlanc]

88′ GMC Suburban, 5.7L 350CI 2WD, 209k Mi.
Project car. Runs great aside from the things which make it a project, hah.

Anyways, currently I’m trying to figure out what is causing my speedo to act up. When driving, about 70% of the time, when I reach over 25MPH the speedo will start making a whirring noise and it will kind of ‘bob’ up and down between readings. I can guestimate my speed fairly well based on watching it’s average and the fact that I’m used to the feel of the car but still, the noise gets annoying. The sound goes away and the accuracy returns when I drop back below 25MPH most of the time. Sometimes it doesn’t act up until over 45MPH, sometimes it doesn’t act up at all. I think it happens more often in colder whether, though it does still happen in hot whether.

From some searching online I’ve read that it may be the cable is kinked or the lube has dried(with the car being 27 years old, this would not surprise me).

Two things
1): What’s y’alls thoughts on this?
2): Is this an issue I can fix/remedy, or should I have my mechanic do it?

Topic

[Lorrin Barth]

I think you need a new cable. Before they went electronic the last cables were lined with some sort of slick plastic. When that wears through you have this trouble.

[Donnie]

^
I have the same issue with my 83 Pickup. Speedo cable was replaced, which stopped the squeaking, but the Speedo head need replacing, before itll read a steady speed.

[Author]

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