speedometer question
Thread Starter
Drifting
Joined: Oct 2008
Posts: 1,369
Likes: 12
From: wichita kansas
speedometer question
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
what typically needs addressed on these things, and can i possibly do it myself? thanks, Rick
Burning Brakes
Joined: Apr 2009
Posts: 807
Likes: 2
From: VIRGINIA BEACH VIRGINIA
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
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,481
From: Southbound
Cruise-In II Veteran
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
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....
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....
Thread Starter
Drifting
Joined: Oct 2008
Posts: 1,369
Likes: 12
From: wichita kansas
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
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
Thread Starter
Drifting
Joined: Oct 2008
Posts: 1,369
Likes: 12
From: wichita kansas
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"
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"
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
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....
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....
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Instructor
Joined: Dec 2009
Posts: 195
Likes: 0
From: Chesterfield Virginia
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
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
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
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.
Instructor
Joined: Dec 2009
Posts: 195
Likes: 0
From: Chesterfield Virginia
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
Instructor
Joined: Dec 2009
Posts: 195
Likes: 0
From: Chesterfield Virginia
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
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
Last edited by Steve's '73; Mar 9, 2013 at 05:39 PM.
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,847
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
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
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