1989 speedo (cable?)

[BerniniCaCO3]

My 1989 GM has a speedometer that jitters in the low range. Maybe 0-20mph, it vibrates, and gets smoother the faster you go until there's no (discernible) vibration.
I was asking a guy at the shop about this.
He had two answers, depending.

If it's mechanical, which uses a long coil spring like a dremel flex shaft going all the way to the instrument cluster,
then it's probably just sticking, and will need to be replaced, or relubricated at the least.

If it's electrical, then it just means the pulses ..I guess?.. are further apart at low rpms/ low mph, and there's not much to be done about it.


I wasn't sure which ours has-- didn't pay attention last time I was under my car. I've got a transmission apart on my bench, but it was a craigslist buy and the speedo cable, or wire, whichever it is, was already gone. I know there's a gear in the tailshaft for the speedometer, so I'm guessing mechanical?
Oh, and the single electrical connector on our transmissions, the round little thin that goes into the valve body and has 4 pins iirc, what is that for anyway? Just curious. Not relevant to the original question, as i know it's not a speedo sensor.

[86VickyLX]

89 is all mechanical baby. Better than those laggy electronic analog jobs. The 89 and down cars use a mechanical cable, attached to the end of the Vehicle speed sensor. that cable goes from the VSS to the speedo head. I've been meaning to replace mine because it makes lovely noises when it's cold out, and does the dance that you're talking about. When you do get a new one, make sure the cable inside the case is going the same way as the one you took out. Otherwise, the thing can act as a screw pump and puke transmission fluid on your pants.

[gadget73]

Didn't Phil have the backwards cable thing on his car when he replaced it ?

I have heard of people pulling the inner core out, smearing it with grease, and sticking it back in there with good results. Never tried it, though I probably ought to. Mine has the jitters too, but the speedo also gets really retarded on mine in very cold weather. ~20 mph will see the needle jumping from 0 to about 50 until it warms up.

[mercurygm88]

Mine jitters a bit between 0-20ish not nearly as bad as it did when I bought the car though. When I bought it it had been sitting about 8 months with just being started and moved around the guys driveway and the thing would jump around all the way up to about 40. I figure ill let it go till it gives up and then worry about it.

[GM_Guy]

Whatever side you pull the core out of is the side to feed it back in, theres a crimped on ferrule that will only let you remove the cable from one side. I do believe it would be from the passenger compartment end (at least on my truck it is).

Grease that baby up with a graphite grease, if you want to be particular, there is speedo cable grease that supposed to stay put where you smear it and isn't supposed to gum up.

http://www.oreillyauto.com/site/c/detail/DOR9/91812.oap?pt=N0825&ppt=C0134

Alex.

[86VickyLX]

Didn't Phil have the backwards cable thing on his car when he replaced it ?

The inner cable was installed backwards in the shield (proper terminology?), not his fault, but yeah that's where I got that from.

[zoomie]

Mechanic,al cable, and the electrical thingy is the nutral safty switch.....ithink but don.t quote me on it.

[Piece-it pete]

Just changed mine. New fitted cables are very inexpensive ($10-15) and come with grease. Super easy. I still have some jitter though.

Pete

[marquisman]

there is two electrical thingies. neutral switch by the linkage and, the VSS on the end of the speedo cable.