[nUcLeArEnVoY]

So my dumbass didn't re-route my upper speedo cable correctly after some exhaust work and for awhile, the cable was resting directly on the headpipe. My '79 has the two piece speedo cable where there is an upper and lower cable joined by a gear adapter/reducer box. Didn't finally notice until my speedometer pointer started jittering all of a sudden during a night-time drive after some carb tuning. Very jittery at low speeds, smooths out a bit at higher speeds - the usual. Makes noise, too; sort of a clangy tick like the cable is thrashing around inside the casing, and you can hear it at the speedometer head. I can even feel it when I remove the trim piece and hold the cable where it connects to the speedo while driving - doesn't feel like it's spinning smoothly at all. So I looked under the car, and sure enough the casing was burned right through to the metallic mesh webbing that reinforces it and the cable itself was just about seized. Not totally, but just about - definitely enough to cause binding further back.

Replaced the upper cable after appropriately lubricating, and routed it appropriately away from exhaust and in accordance with service manual specs and fastened to the factory clips with no kinks and soft curves... no difference. Still jittery and making the ticky sound. So I pulled the lower cable and noticed a slight obtuse kink where it connects to the nylon driven gear; maybe that's the issue, and so I'm about to replace the lower cable with a NOS 27" inch unit I grabbed off eBay as well as the speedo driven gear to see if that does the trick. The nylon driven gear doesn't look damaged at all on any of the teeth, and from what I was able to glance at on the drive gear itself in the tail housing, it looked fine, too. But I figured, may as well replace the driven gear while I'm at it.

So if replacing the lower cable and nylon driven gear doesn't work, that leaves the drive gear, (god, I hope not...), the reducer/adapter box (which I doubt since it spins freely and smoothly), and the speedo itself. I'll tackle the speedo before I pull the tail housing off the trans, for sure, so does anybody have any recommendations on a good, reputable company to send the speedometer to for a refurbishment? I'd do it myself if I had some guidance on how to restore them, but I would think these are very delicate units that were never actually meant to be serviced or repaired. Speedo is a stock 100 MPH unit for 1979, with the yellow/gold KPH lines/markings - this rules out replacing the speedometer since the current repros have the blue KPH lines/markings, and I would like the car to remain original.

Thanks!

[Trevor78]

No joyful future?

Regardless of repair, you could probably pick up many a decent used speedo even just to test and be well ahead in costs. They tend to be fairly indestructible compared to other electrical gauges, just have to select the option you want and find one with good lettering that someone hasn't tried to wipe with cleaners.

[Hoodshaker]

Pete Serio at Precision Pontiac is the guy to go to for this. http://precisionpontiac.net/Rally_Gauges.aspx
Search his name here and you'll find plenty of testimonials.

[nUcLeArEnVoY]

Originally Posted by Hoodshaker

Pete Serio at Precision Pontiac is the guy to go to for this. http://precisionpontiac.net/Rally_Gauges.aspx
Search his name here and you'll find plenty of testimonials.

Exactly why I was looking for, thank you!!

I still have to install this new lower cable and see if that's what went wrong, since I'm waiting on some seals for my original speedo driven gear housing bullet plus the gear itself, so hopefully I won't need to send out the speedo. But if I do, I'll send it to this gentleman. Thank you !