What would cause speedo needle to stay at 20mph when I'm sitting still after a drive?

[5spd GT]

Well I have been having a bouncing speedo problem all the way to 70-80mph (real irratic between a 15mph span or so)...and well a couple days ago I noticed that I'm running 15-20mph slower than what it is showing on my speedometer. It kind of just came all at once

So anyways...now I noticed a couple times that my needle is stuck at 15-20mph when I just pull up somewhere and stop??? Why is that?

I'm hoping it is the speedo gear...but after I put in a new speedo cable it got worse (the bouncing)...

Anyways...just wanted ideas...though I have an idea what it could be...

Thanks

 

[speedytang]

The cable is new but it is still binding. The cable is winding up because either your speedometer is catching and causing the cable to do this or your cable is bent wrong coming out of the transmission causing the bind. It is usually the bend coming out of the transmission. To test this unscrew the cable from the transmission to lay it flat and hook a cordless drill to the cable and watch the needle and when you turn off the drill see if the needle drops to '0'.

 

[5spd GT]

Thanks speedytang...I'll have to check that out...

I think I'm going to get a new speedo gear as well when I do that...

 

[Swarzkopf]

OH NO! You're car has developed the dreaded speed locking problem! Your car can never stay parked or sitting at idle, it will always move at 20mph due to this fatal issue. Your only option is to junk the car and get a new one. Sorry man.

Good luck with it, hopefully speedytang is right on.

 

[5spd GT]

OH NO! You're car has developed the dreaded speed locking problem! Your car can never stay parked or sitting at idle, it will always move at 20mph due to this fatal issue. Your only option is to junk the car and get a new one. Sorry man.

Good luck with it, hopefully speedytang is right on.

Lol...anyways...

The bouncing speedo I had got worse when I put in a new cable with that lube that comes with it. It is green and sticky...I put it on the whole cable...isn't that what I'm supposed to do??? I didn't put any on the ends...

 

[HISSIN50]

curious. bump for prime time.

 

[5spd GT]

Well now (as of today) the needle is stuck at 40mph when I'm sitting still It was at 20-25mph yesterday???? Eventually it will probably be at 100mph sitting there.

It is bothersome when your doing 60mph and the speedo says 100mph

 

[ALMOSTFINISHED]

Maybe the magnets inside the speedo itself have worn out and are sticking. If ya know anyone with another stang, swap out the cluster and see what it does. It might be time for a speedo recalibration.

Nick

 

[5spd GT]

(bump)

I have been told that I could spray some wd40 in the guage and clean it out because dust will get in there and make it stick? Sound feasable?