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No speed or miles, found 3 unhooked cables

LanceB

Well-known member
Joined
Jul 18, 2003
Messages
455
Location
Louisville
Corvette
1981
OK on the 77 speedometer and mileage don't work. I found 3 cables that are not connected. 2 of them go into the same unit (something that is near the brake master cylinder), one of these cables comes out of the firewall, the other goes under the car, and they screw on to two fittings on the unit. One of these cables looks hollow, the other has a threaded wire in it, it looks like it may have a broken end, but I can slide this cable w/ threaded wire onto the unit and tighten down, but I don't see how this cable would connect to anything, I don't know if the other one is a vacuum line or something from the unit or if it is supposed to be hollow.

The 3rd wire I was able to research in a repair manual. It is definitely cruise control related (which doesn't work either). It comes out of what is called the "servo?" which is unit with a rubber boot that hooks to this wire/cable with a ball type cable (like something you would pull a bath drain with). The wire coming out fo the spongy rubber boot (that connects to this ball thingy) is frayed. The end stops near the carb and this is where it was disconnected. The manual describes it being connected to the carb. But there is a cable coming out from the firewall that already hooks to the the carb that is very similar to this one. I noticed next to the one already connected to the carb is a square opening the cable can snap into as if it was made to go there, but once it is fitted in it, I don't see the end being able to reach anything. Possibly my carb is missing a part to connect this?

Anyone make sense of this? I will try to provide pictures if would help, trying to describe best that I can.
 

LVMYVT76

Well-known member
Joined
Apr 21, 2006
Messages
664
Location
springfield, mo
Corvette
1976 medium blue
The two cables going to the cruise control servo, one is from the transmission and the other goes to the speedometer. If the servo is broken, you might not get a reading at the speedo. You can bypass the cruise control and get a cable that goes from the transmission directly to the speedo. the cable going to the carb, if it is defective, they don't make these for replacement(if you find a new one let me know). You may find one off a wrecked car, but they are hard to find. This was only used on the 77's.
 

LanceB

Well-known member
Joined
Jul 18, 2003
Messages
455
Location
Louisville
Corvette
1981
Thanks for your advice. The speedo worked before, now I am thinking someone has already by-passed the cruise before. I am looking at the 2 cables that go into the transducer that were disconnected. The one that screws in the bottom is definitely the speedo from the transmission, there is a wire in it that one that slides in the transducer. The one that screws into the fitting on the transducer on top of this one comes from the firewall and it looks hollow (no wire in it). I am going to change the speedo gears and try turning the wire from the transmission and see if it turns. Maybe a new speedo wire and grease are all it needs or a bad transducer (I hope not). What do you make of this?:confused
 

LanceB

Well-known member
Joined
Jul 18, 2003
Messages
455
Location
Louisville
Corvette
1981
Hmmm...so I am assuming since this goes through the firewall that this square cable actually goes to the speedometer? Do I have to pull the speedo to replace this cable or do you think I can get to it from under the dash? Wonder what happened to the cable. Could a piece be stuck in the transducer? Also I am looking at the cable that has a wire in it, it sticks out about an inch, does the transducer just read the revolutions when it spins? Sorry for so many questions, really want to know how fast I am going!
 

6880 Mike

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Joined
Jun 30, 2006
Messages
2,723
Location
The Bluegrass State
Corvette
1968 convertible; 1980 L-82
M-335.jpg


Got the '77 AIM? Lower cable shown, but you can see the square cable inside the sheath.

:)
 

LanceB

Well-known member
Joined
Jul 18, 2003
Messages
455
Location
Louisville
Corvette
1981
I don't see a wire in my speedo to transducer cable, so I think this is my problem. I can get under the dash and see the speedo cable (and get a hand on it), I am trying to disconnect, looks like if I remove a clip it may come loose. I hope I don't have to take dash out to disconnect it and replace it.
 

LVMYVT76

Well-known member
Joined
Apr 21, 2006
Messages
664
Location
springfield, mo
Corvette
1976 medium blue
You do have to . The cable can only go in from one end, and that end is behind the speedo. There is a clip on back of the speedo to release the cable housing. Then you can either replace the complete cable and housing, or replace the cable itself.
 

LanceB

Well-known member
Joined
Jul 18, 2003
Messages
455
Location
Louisville
Corvette
1981
Never removed the dash before, but I guess I am going to learn about that now...any advice before jumping in on that?
 

ratflinger

Well-known member
Joined
Sep 4, 2005
Messages
74
Location
South Central Texas
Corvette
1979 Black Coupe, 396 SBC
Whiskey helps as does removing the steering wheel. The clip is a push clip, push it towards the front of the speedo & that releases the cable. You MAY be able to do it w/o pulling the dash.
 

LanceB

Well-known member
Joined
Jul 18, 2003
Messages
455
Location
Louisville
Corvette
1981
Removed Cable!!!

I got it out without taking the dash out! Looks like I can replace it rather easily. Only thing I am worried about is why it would have broke in the first place. It broke at the end where it connects to the transducer. I can see the square plastic needle on the end of the speedo, this is gone on the end of the transducer.
 

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