Ok, so I'm driving today and my speedometer starts jumping around, and after I come to a stop and take back off....it doens't work. Please provide me with some starting points to check out.

TOMP, I know you're replying, and remember that this is a 92 Firebird. I seem to recall that the Birds had a lil different speedo setup than the Maros.


Thanks guys.

 

I would say the jumping was the cable binding.. the no operate is it so wound up it cant move. try unplugging from trans and letting it "unwind" then pull it from above and spray some lube doen the opening. That might help prevent it from happening later...

 

So I do have a cable? I've been told that it's all VSS.

 

maybe the worm gears in the tranny that the VSS is hooked to have worn a tooth or three?

 

It would help me out a lot if someone could post where the VSS hooks into...that way I can check to see if it's come loose.

 

Pix help.

 

Look at the tailshaft of the tranny. There will be a connector on the drivers side. That's the VSS. You should be able to pull the sensor out and see if the gears are stripped. I have no idea why they would strip though......did you throw a code 24? Also, does your TCC still lockup? Check the wiring also.

 

My convertor locks up (I think..haven't driven too far) I'm thinking maybe a connection came loose? ????

 

Replace the VSS... write down your RPO codes and go to the parts store. They'll have like 5 to choose from. Order the one that matches your RPO. It takes about 5 minutes to swap, just pull the clamp bolt, pull out the old VSS and put the new one in, tighten the bolt again and you're set to go.


My VSS did a slow burn, it would work from time to time but the longer I waited the more it didn't work.

 

Drew, how can I be sure it's the VSS. Right now I am EXTREMELY tight on money so I need to be sure that whatever I replace is it. I just had to replace the shifter cable w/ an OEM one (Aftermarkets suck and didnt' fit right...I tried) so that sucked.

 

Well, there's no way you have a cable.. unless someone swapped the panel and VSS, which is pretty darn unlikely. Yeah, all the speedo's were electric, starting in the very late 80's. I think Firebirds got 'em in '87, and Camaros in '88-89?

I wish I could provide a diag chart for ya, but it won't be in my '86 GM Manual. Hey, I wonder if this circuit stayed the same in later years? I could check out my dad's 88 a-body manual, and 92 blazer manual. There's gotta be a way to measure the output of the VSS to see if it's constant... and if it was, that would mean the speedo would be the culprit.

But Drew did say this same thing happened to him! Are you near any junkyards that you could pull a VSS from?

 

Well if you'd rather troubleshoot...
unplug and reconnect the plug tot he VSS, see if it works
remove the guage cluster and check the speedo circuit board for melted trace lines
This also reseats the cluster.
You could also pull the VSS and the tailshaft on the tranny and check the gears to see if they're stripped or missing teeth.

I did all of the above then I spent $30 on an aftermarket VSS and had it fixed in 10 minutes.

Mine never really gave up the ghost, it just wouldn't work from time to time, it'd read 15mph lower than the actual speed when it did work, etc... after reassembling everythign and checking it all out and recalibrating the speedo, I wished I had just replaced the VSS.

 

Drew...after reading (and I may still be mistaken) the VSS controls TC Lockup, right? My TC does still lock up. Is it possible for a bad VSS to still lock up the convertor?

 

TTT

 

Yeah, when the computer sees 35 MPH from the VSS, it puts the TC into lockup. Will your trans always do lockup, even while the speedo is jumping around?

 

Speedometer doesn't jump anymore...it doesn't move at all!!! It only jumped that one time...after I came to a stop, hastn't moved since. Today all my gauges went out. I replaced the fuse and they work fine now Haven't checked to see if the speedometer works again now or not, but seeing as how the other gauges were working before without it, I doubt it will. Then again, you know how cars are sometimes . Is there a seperate fuse anywhere for the speedometer?

 

I don't have any data about the newer f-bodies, but I don't see why the speedo would run on a separate fuse.

 

Well, all my gauges went out again. I plan to take apart my dash tomorrow and see if just old age might have cause wires to rub and wear thin.