We have a problem with one of our trucks. It's a 1984 Chevy Blazer. The Speedometer will only go up to 35, but of course the truck will go faster. I know the transmission is new...so maybe it has something to do with it? I'm guessing since its old, it has a speedo. cable? Can this cause this problem? I know its a chev, but does anyone have any idea what it could be?

 

Speedo cable problems don't discriminate between brands....

Could be the cable, the gear--chipped maybe, maybe a stuck speedometer unit.....

 

yeah Im thinking possibly the cable, could also be that gear inside where the cable goes.

 

Sorry for the way late udate:

More info on it. The speedo doesnt mark anything right at all. Say im going 10mph...it'll mark around 5mph. Also, when it hits the 30mph and gets stuck, it starts bouncing up and down. Very odd.

 

Does it have cruise control? If so, does your cruise control work? I ask that because on trucks with cruise, GM used a big cruise control driver with 2 cables. One from the tcase up to the cruise driver, and once from there to the speedometer. Point is, you might be lucky and it might only be the short cable from the cruise module to the dash.

Just a thought.

 

If the needle is moving at all, that means the cable is intact. I'd say check the guage itself...maybe something mechanically wrong with it.

Being a chevy and all....

 

When I worked at a Chevy dealer in the 80s we had an account with the "local" speedometer shop to fix the Chevy heads because you use to fix them instead of returning them under warranty. Not unusual to drop off 2-4 a week. I would not be surprised if the head was bad.