new2-80vette

I just recently bought my Uncles 1980 corvette from him and it needs some work. I have already done a fair amount of homework on the problem areas and have just started spending money.

I have run into a problem when finding out how to repair the speedometer (stuck at zero with no movement). I was hoping it would just be the cables but I have removed both and they are both in good working order. I have also checked that the speedometer moves as the upper cable spins. So... I think I have it narrowed down to the Speed control transducer (the box the two speedo cables run into). I am not positive that this is the problem and do not want fix it if it isn't broken. How can I be sure that the transmission is not the culprit?

Also if this is the problem how much am I looking to spend?

Thanks in advance...

speedreed8

i had same problem on my 79, i did like you and removed upper cable, turned it and speedometer moved, i disconnected the lower cable from the trans, and turned it with a drill , and nothing. i removed both cables and installed a single cable (car W/O cruise cable) from orielly auto. ($22) the rebuilt transducer unit is about $129 from most vendors. i temporarily removed the transducer for now. good luck

0Willcox Corvette

Speedreed is right, bypassing the transducer will get you going.

If you want your unit rebuild we do them, here is the link: http://willcoxcorvette.com/product_i...ducts_id=12661

We will only build your unit, we do not do these on exchange basis any longer.

Willcox Inc.

blk79nj

I did the same thing on my '79. It could also be the gear in your transmission, but I would try the one cable first.

new2-80vette

I am reluctant to try the single cable because If at all possible I want to keep the car functioning as designed. Any other suggestions???

Thanks for the help thus far!!

photomike_

79 vette speedometer didn't work...Replaced transducer then drove car, speedometer worked for about a mile then went out AGAIN!!! any help???

7T1vette

Since you will be under the car anyway, I would recommend that you take the cable loose from the transmission and remove the cable drive gear to check it out. The gear is plastic and it connects to the cable via a square 'hole' in the shaft of that gear. That 'hole' can get cracked or rounded-out over years of use. With the cable loose, it may turn OK...but when some resistive load is applied, the drive gear just spins around it and nothing happens. If that gear 'hole' is worn out, you can get another drive gear at about any car parts store or at tranny parts internet site via mail order. If the drive gear is still OK, the cruise head is your problem. It has a 'friction wheel' inside of it which can slip to the point that there is no output to the speedometer. Good luck.

new2-80vette

Sorry I didn't update earlier but I did find the problem. What had happened is the lower cable that runs into the transducer had actually broken off at the transducer. The first time I looked at it I didn't check to see how long the square plastic piece (red) except that it was there and it spun the cable. I came to find out after a second look that half of it had broken off into the transducer. All that I had to do was get a new cable ($20) remove the broken end from the transducer and screw in the new cable. The new cable is all metal so that the plastic end doesn't break off in the transducer again when it gets brittle. The job only took about 15mins and now the speedo works great. Good luck!!!

blk79nj

Just keep an eye on it. When the transducer goes bad, it gets harder to turn, which puts more tension on the lowere cable. Thats why the lower one will always be the first go... The good thing is that it's also the easiest to change.

7T1vette

The fact that it broke in that manner may indicate that the lower cable is seeing more stress than expected. If the same thing happens again...or if your cruise speed doesn't hold steady...it would probably be a good idea to pull the cruise transducer and check it out. It is not a complicated piece of equipment and someone with decent mechanical abilities can take it apart, clean it up and check the condition of parts fairly easily. You might want to 'plan ahead' and search for some info on check-out/maintenance/repair of a GM cruise transducer; they are all very similar from late 60's through late 70's (until they changed to ECM based cruise circutry). Once you are familiar with how one works and what parts are in it, you should have no problems doing so.

new2-80vette

Thanks for all the suggestions I will plan on taking a look at it again. I don't want to burn through anymore money/parts than I have to.

tonyponykay

my 80 vette has exact same issue, i undid the bottom cable and I think its broken at transducer, a white plastic piece is stuck in the transducer, the there's nothing on the endof the cable cept the stub of the white plastic ..

funny that the top cable hole in transducer looks different than the bottom one, the top one looks like what the bottom one looks like at transmission,, but the bottom one port on transducer has a copper piece sticking out, i guess the plastic piece goes inside... wierd..

can't find a proper diagram of this on AIM, so wondering what to do.. how hard is it to connect speedo cable to the speedometer at dash?

can a large man with large shoulders and neck injury get under there to do it? I don't think its possible ... I wonder cause i wonder if I could convince my wife to slide under the dash... how difficult would be the connected of the cable to the gauge?

thanks
tk

Roger Selzer

On a 1980 Corvette, how can I troubleshoot the cruise control system (transducer and turn signal lever switch). Roger

hugie82

My Cliltons manual had a very detailed fix for the vette cruise control system.

hugie82

If you can turn the tranducer with your fingers with easy and see both inlet and out spin without the square holes being striped out than your good as far as your speedo working. My top cable was binding and when it warmed up from the friction. It would bind up and break.
I had too ream the cable casing out and oil her up with lithium grease.

To test your speedo just have someone sit in the car and turn the upper cable by hand quickly. They will see the speedo jump if it works.

Roger Selzer

Thanks, but my speedometer works fine. What i'm asking is how do I troubleshoot the cruise control system, i.e., the criuise control transducer, and the cruise control/turn signal lever switch? - Roger

BLK89Corvette

Do they make an adapter to connect the 2 cables together? (upper and lower) to avoid going under the dash and doing one longer cable?

REELAV8R

Found this. It might do the trick. You'll have to measure, or figure out the size of your ends to see if they match up.

http://www.ebay.com/itm/like/360670239826?ul_noapp=true&chn=ps&lpid=82

Blondie - C3

Did you try the patch cable option ? I have the same thing going on my 81.

M Pete

I'm bumping this up to see if anyone has an answer to the last question.