Just bought my first Corvette. 1982 with CFI. Speedometer needle shakes from 5mph up to 75mph. Do I need to replace the speedo or cable? Also dash lights are dim when control **** is all way up. Do I need a new controller / switch or do I replace dash bulbs.
Looking forward to any suggestions - Thanks - J

 

I am in the same situation right now with my 78 . First thing to check is the cables . From what I understand the lower cable is usually the culprit . If you have cruise control there will be an upper and lower cable . Check the cables first . If the cables are good the cruise control transducer is usually the culprit . This is the case with my 78 . You can find the transducers at ecklers or one of the other vendors here . I hope this helps . I am sure others will chime in . I am not a mechanic just relaying my recent experience . Good luck .

 

First of all welcome to the forum, lots of good knowledgeable people here.

OK, as to the speedometer cable, does your car have cruise control? If so, then your speedometer cable is actually two cables if it is still original. These cables meet in your driver's side fender well in a device called a transducer (this controls your cruise control). Easiest way to find it is to trace the cable from the firewall. Once you have it, disconnect it
from the transducer and hook it up to the chuck of a cordless drill. Run the drill in REVERSE slowly and see if your speedometer needle is still jumping, if so then this cable needs replacing. There is a second cable that will come out of the transducer that runs to your transmission (or one cable directly from speedometer to transmission - depending on your situation). This cable needs to be unscrewed from the transmission and the end of the cable checked to see if the plastic tip at the end of the cable has "rounded off". This plastic tip has a corresponding "driven gear" in the transmission that actually turns your speedometer cable. Since both are made of plastic, the square profile they start out as eventually wears and they "round off" and cause your needle to dance.

I had the same issue with my '79 and was lucky enough to get away with just replacing the lower speedometer cable. The driven gear can be sourced from any vendor here on the forum. I don't think your year had too many power train options, so your choice to replace the gear, if necessary should be minimal.

The vendors also carry complete bulb kits (kind of a one stop shop) for the interior, but of course any auto parts store can hook you up there.

I would highly recommend two manuals. First what we all here refer to as the AIM or assembly instruction manual. This is a copy of what the line workers in Kentucky used to build your car - very informative. Second would be the Chassis Service Manual that the mechanics used to service your vehicle at the dealership. Both are invaluable if you plan on turning any wrenches yourself.

There is also a special "sticky" at the top of the C3 section devoted specifically to '82's, so that should prove helpful with any specific questions you may have.

Enjoy you new car, you're in for quite a ride.........literally.

 

what he said . Nice write up .

 

Thank you Guys. I will try this over the next few days. I was debating whether or not to go with the 1982 CFI as I heard it can really be a headache. Was looking at an '81 but this one really had me. I need to also see why it idles hight round 1200 rpm. Even after warmed up. I am assuming these manuals can be bought on eBay too.

Thanks

 

TBI 1981-82 Vehicles-Idle Mixture

Idle speed and mixture are controlled strictly by the computer emissions system. Do not attempt to adjust the idle speed or mixture as these functions are controlled by the computer.


You may need to have a shop possibly adjust the idle speed. The idle speed is controlled by an early model control system.

 

I wouldn't do anything until I checked carefully for a vac leak. This is the most common source of a high idle.

 

Let's see some pictures of this bad boy. Also, I have followed along with interest as Arky has worked on his '82. IMO he would be a guy I would definitely bounce any questions off if I was running an '82. If your comfortable with it, fill in some info in your profile; you may find someone on the forum close to you who can help you out.....or just find guys to hang with.

 

before you go buying a new cable, if in fact you determine it's the problem, I'd just put some lube on it. I just did exactly that on my 79, and it's 99% better. It was bouncing about 10mph back and forth on the interstate. Now it just barely bounces at all. I may take it back apart again for a little more lube and see if that helps. I was able to do my non cruise control 79 by just unhooking the cable from the back of the speedometer and pulling the cable inside the sheath out, lubing in and sliding it back in, and reconnecting to the speedo.

 

I had the exact same problem (both the dim dash/cluster and sporadic speedo) with my 78 and inadvertently fixed it yesterday while replacing my bulbs . Here is what I did. For the dim dash and cluster, I changed out the bulbs with new LED bulbs. Much brighter and worth the $20 for all of them. The center cluster comes out pretty easy (4 screws and 2 bolts through bottom - you will have to take off the side panels to access them). For the speedo, leave the panel in the dash and just unscrew the lens and then the 4 hex bolts on the cover. Then take out the hex bolts on each of the instruments and pull them out. The speedo will have to be pulled out part way and then disconnected from the cable - the tach will just pull out. I figured I should clean up the contacts, re-greased the speedo cable connection while it was out. Took it for a ride at night to actually see the panels (much better) and noticed the speedo was not jumping around anymore! This will also give you access to all the bulbs in the dash to replace. Of course that is the easiest scenario, but worth starting there. HTH.

 

Thanks for the feedback and tips. I noticed one cable from speedo thru firewall going directly under the car. It doesn't hook to any cruise control module. I am assuming it goes to tranny some where? After pulling the cable out of the sheath is it tough to put back in and realign?

Jartanyon where did you buy the LEDs?

Pics soon

 

Your speedo connects to the tranny right above the pan on the driver side.

I bought them off of Amazon - need two sets for both cluster and dash.

 

Thanks for the info.

 

bump

 

Is it possibe to unhook the speedometer cable at the transmission and pull the cable out of the sheath from that end, relube and slide it back in? I have the same problem with the speedo bouncing around, and I know it would be much easier to access it from under the car vs trying to do it from the top side in the dash.

 

Bump

 

I dont know the answer to your question, but I can tell you that it is not that difficult to do it through the front dash panel. I would think it would be more of a hassle pulling it out through the bottom than just pulling off the lens, housing and gauges. It shouldn't take more than 30 minutes and you get to sit in your car instead of being underneath it

 

The last time I had my dash apart, it was quite a task and even after removing the dash pad, trying to reach the back of the speedometer gauge low enough to reach the cable was extremely difficult. I have a car lift, so unscrewing the cable from the transmission would be much easier. I am just not sure if the cable can be pulled out of the sheath from the bottom side, lubed and then reinstalled.

 

Thanks Brian - I appreciate the help and advice -