speedo's broken

[BillyBob]

Since buying my '77 a few months ago, the speedo's always been erratic (bounces between 40 & 60 mph at constant speed of about 50 for example). Several weeks ago I began hearing a speed-sensitive ticking - almost as if a wheel spoke was rubbing something on each turn (which it wasn't), or possibly as if it were a stone stuck in a tire (also not). A few days ago, the speedo began working intermittently. So, today I disconnected the cable at (auto) trans and, magically, the noise stopped.

The question is; what's the most-likely cause, and what's a likely source for repair parts?

[Gunslinger]

Sounds like your speedometer cable is in bad need of lubrication. You can try squirting some lubricant down the length of it or pick up an adapter (NAPA, Snap-On, etc.) so you can attach a grease gun to it and lube it that way.

Try that and if it doesn't do it, you'll need a new cable.

[BillyBob]

Speedo once again functional - it was the 'cruise control' servo. Speedo cables were replaced with a one-piece unit, by-passing servo.

FYI: 'cruise' was non-functional as it was missing, as a minimum, the turn signal stalk-mounted controls. I understand the servo currently has no rebuild capability. Can anyone confirm?

[Gunslinger]

Depending on their construction, servos can be rebuilt. I had a '78 Corvette that had a bad servo and found rebuilt servos (for a Vette) are very available.

I would think a lot depends on whether the cruise control in your car is an aftermarket system or one from GM or some other major manufacturer. If an aftermarket system you may be out of luck. If a GM system you can probably get a replacement.

If your cruise control is a GM unit, try looking at companies like Corvette Central, Ecklers, Late Great Chevies, Year One, etc., and you may be able to match one up.

[BillyBob]

OK & thanks!

So, there's possibility the servo can be rebuilt...still missing stalk-mounted controls, as a minimum. Assuming I can find/get that, next question is, 'what electrical is there/is missing?'

While there may be value in cruise control pieces and parts, will save that project for another day.

Again, thanks for suggestion of places to look! Yes, I know, the Hunt is much of the fun in old cars.

[Gunslinger]

I have no idea if the cruise control used is a stand alone system or tied into the car's electronics. Being a '77, there are likely no electronics to speak of, so my guess would be it's stand alone. That would make it easier for finding and using parts.

You'll have to determine if the steering column used was GM, AMC, Ford or Mopar to get the proper turn signal stalk and wiring. I would check with Dan Booth at Nostalgia Motors...he lists a number of different turn signal stalks, depending on the year. Whatever manufacturer the steering column came from should give you an idea of where to source other parts.

If the cruise control is an aftermarket that Avanti used, all bets are off on finding replacement parts. The maker may or may not still be in business.

You can always buy a new aftermarket cruise control...they are available.

[BillyBob]

Mine's an AMC column - yes, probably AMC stalk unit.

...I'm impressed with your commitment and dedication to keeping the cruise and making it functional!

[Gunslinger]

BillyBob...

I happen to be looking through some older issues of the AOAI magazine looking for some other information and ran across some info you can use.

According to some interchanges listed, the cruise control bellows is a Mopar Jeep-Eadgle unit...part number J3226540.

The cruise control switch for the turn signal lever is Speedostat #250-3020.

Another interchange with no part number is that the "cruise control unit" is the same as American Motors units during the same years.

I don't know how good those numbers are or what their availability is, but it's a starting point.

[Gunslinger]

In AOAI issue number 101 there's an article on servicing and repairing the Dana speed control. If that's the one you have, and don't have that issue, send me a PM and I'll make a copy and mail you the article.

[MikeValent]

In the Avanti electrical schematic drawings available on Bob Johnstone's website, there's an AC unit from 1976 shown on page 19A, and a Dana unit from 1981 shown on page 19B. I didn't print out 19A since my Avanti has the Dana unit, so I can't promise that it'll be of help to your but it's worth a try.