razman

my 68' speedometer is cosmetically perfect (face plate, needle, color, etc) but mechanically it seems to have a few glitches. i hooked up a cable to it, and chucked it to a drill motor, the needle responds, but jumps all over the place at a constant RPM....plus the odometer does not advance. is this something that a person with pretty good mechanical skills can tear into and fix, or does it require someone with more experience. i have the complete speedometer out of the dash assembly, but have not removed the back of the speedometer from shell. (i don't want to end up doing more damage or have any surprises)

what typically needs addressed on these things, and can i possibly do it myself? thanks, Rick

dgood

I know that Willcox will overhaul them for you. I looked at mine (everything was broke inside) and it was too small and some of the parts were not available on line. there website is www.willcox.com

Scratch

Any speedo repair places near you? They may be able to overhaul for ya.

Easy Mike

Yes. You can replace a speedo head. You might want to touch base with your DMV concerning odo replacement since the new one will read zero.

mrvette

IMO, the head end is the problem, and the odo is not an issue....

it's a simple gear reader off the head end....

you maybe try shooting some graphite down the cable, or up the cable....

or WD 40 works almost as well, really, here in FLORIDA anyway....


IF you need it, I have a head end, and it's not all that complicated, what you WILL hate is the R&R from the car....and so to modify the wiring so you will live longer over the aggravation....

razman

the speedometer is out of the car, as is the dash, and the entire interior at this point, so no prob there!

so at this point, i have the entire speedometer unit detached from dash unit all in one piece ( bezel, face plate, needle etc, all the way back to the cable connection)

when you say "head end" are you talking about the rear end of the instrument? (the portion that the cable attaches to?) do i simply carefully pry the needle from the face and take out a few bolts to separate the two pieces? someone else has suggested that "lubing" the inside of the speedometer may lead to more probs down the road, i dunno? am i on the right track as far as taking this thing apart to see what i have going on inside? i just don't want to damage an otherwise perfect original speedometer (cosmetically anyway) thanks, any more info would be appreciated. Rick

razman

well, i tore into my speedometer last night, this is what i'm down to, and i'm sure the problem is in here. (bench tested, needle goes smoothly up to about 40mph, then PEGS OUT, and makes high pitched noises)
is this the "head end" that was referred to? also, forgot to mention, the odometer or tripometer does not advance during bench test...where to go from here? lubrication or not? checked locally, and can't find anyone qualified to work on "old mechanical speedometers"

mrvette

Raz, as with back channel .com......the unit I have is not a screw on speedo cable, but has a large spring clip holding the shroud in place....

second off, is the forward construction is muchly different, it will NOT work for your install.....

Love your money, but IMO, It's a NO GO.....

like I said 69-77.....GM went the plug in and changed a lot of crap around in all their cars in them early years of production, some dozens of UAW got sore thumbs from screwing on shrouds all day long.....not that I blame the guys, really....

Steve's '73

Next step is to check the three worm gears:

Courtesy of Wilcox



My advice to you is send it to Wilcox. How are you going to calibrate it after?

I tried this:



But, all I ended up doing was wasting time I eventually sent it to Wilcox and it's been working great ever since.

Steve

razman

thanks Steve for the info....how much did it cost to send to Willcox for repairs and calibration? Rick

Street Rat

I've got some speedometer repair places located. That is if you don't send it to Willcox. I would suggest Willcox first as they are a forum vendor. PM me if interested.

TimAT

If youre looking for some place closer to you, there is a load of aircraft instrument shops around Wichita. Let your finger do the walking. If all else fails, Metro Speedometer in Independence Mo did mine for $125.

Steve's '73

Rick,

It's been a while, but I believe it was in the $140 range. Probably varies depending on how many worm gears are bad. If you’re still inclined to do this yourself, the retainer holds the speed cup. Inside the speed cup is a tensioned spring. By moving the horizontal bar on the retainer you adjust calibration up or down.

There’s a possibility that yours doesn’t need calibration. Changing out the worn worm gears might be the fix. But, you certainly don’t want to put the dash together and find out your calibration is off.

Steve

razman

thanks again Steve...where do you get the worm gears? i haven't seen them at most vendors?? Rick

Steve's '73

http://keenparts.com/pages/search.ph...x=0&submit.y=0

http://www.corvetteamerica.com/cf/di...%20speedometer

CA Part # 1604

Or call the shops that repair them and see if they'll sell you the worm gear you need.

Steve

0Willcox Corvette

1968 was the last screw on cable Speedo/Tach, in 69 GM went to the clip on cables. They will interchange and all the components are the same with the exception of the actual housing. (you have to change the cable to a 69).

The first worm bushing is what fails in these old heads. Failure allows the first worm and magnet to move out of alignment with the second worm and this eats the teeth off the first (A) and second worm gears (B). Adding a new gear may get you going for a while but it would only be a bandage.

A new issue that is popping up more and more often is the actual odometers wearing out and locking up and when this happens the gear C on the third worm takes the hit…

IMHO..

Willcox