Well, I knew it was a long time coming because the needle had been bouncing unsteadilly ever since I bought the car. But tonight, whilst driving home, it was working as "normally" as it ever had, and then just dropped to zero as if it had been disconnected. I don't think it's coming back, either.

This is an '89 IROC, so I know it is a mechanical (non-electric) speedo. However, I've never serviced one of those so I'm not sure really even how one works. I'll have to check, but I think it's safe to say that the speedo-cable connection down at the tranny--and the gears within--are just fine (the were last I checked).

Any ideas on what I need to be checking, and what I will likely need to replace?

( If it helps to narrow things down, I will say that I occasionally heard a very audiable "scraping" sound come from the dashboard that varied with the speed of the car. It sounded almost like a metal disc spinning against plastic. This would continue until I stopped the car, at which point it no longer made the noise. )

 

sounds like the line inside the speedo cable broke.... same thing happendd to me on a different vehicle

 

You think this is something that can be easily serviced from within the dash inside the car, or will I need to go tracing that cable all the way down to the tranny?

 

This probably won't be a surprise to any of you who have had this problem, but I just drove the car again and noticed the SES light come on when I got on the highway. I checked the codes when I parked, and got a code 24: "Circuit fault in vehicle speed sensor".

Couplea questions:

1. Where is the VSS located?

-- and --

2. What are the consequences of driving around with the ECM not knowing how fast the car is going? This is a MAF (not SD) car, so hopefully this isn't as critical in this case.

 

ur guess is as good as mine on that one but does make better sense

 

As far as the emc not knowing how fast the car is going, I believe it gained power from it, perfect example here (and the one I was referring to) is my first vehicle a 1988 S10 Blazer I bought it for 50 dollars and built it and wired it end to end, the motor and trans came out of 1991 S10 truck with electric speedo and it ran pretty fast and so when I put it in the blazer it didn't run any different, except a constant check engine light but it would pull the front wheels from the ground if I mashed to the floor (not enough to brag but it won me a lot of money) although I,ve goten racing tickets, spent time in jail over racing and at least 12 speeding tickets were caused because of no speedo (but that only was cuased by no speedo) I had fun but it shouldn't hurt if not help.

OH yeah the VSS should be located in (or on) the tranny or on the back of the dash cluster, if not there it should be on the firewall.

 

Remove the cluster. The following link will provide some info on that as well as some other suggestions on speedo heads:

https://www.thirdgen.org/forums/faq-...-fix-pics.html

Once the cluster is removed, simply grab the speedo cable and pull. If the problem is there, I'd recommend pulling the cable housing at the tranny end and thoroughly cleaning it (I used brake cleanerm, IIRC), before replacing. I don't know if you'll have a one- or two-piece cable. If two, I assume that the break could be at either piece.

The Vss box is on the backside of the cluster. You can see it in the above link.

JamesC