I actually had the same problem the other day, passed some guy, got up to 120 (km/h) then it started bouncing from 120 up to 140, back and forth, and did't stop till i went back down to 100, then it didn't do it again.
there have been several threads about this, even since I've joined. Several different possibilities and opinions. Try search under "speedo". Could be the cable; could be the guage bushing needs some grease.
serious? thats kinda screwy. The lower mileage thing wouldnt matter, you have to get it certified if you swap it, and if you dont and then re-sell to someone, and they determine that the vehicle has more mileage than what the speedo says, then you get a fraud charge and a $10,000 fine, and jail time.
i came across the same problem, so i took the speedo guage apart. i found that the little spring that controls the way the needle comes back down got tangled somehow.
you have to get a replacement spring, or just change the speedo guage itself form a j/y.
you can try to untangle it, but it will not be accurate.
yeah... i just installed c/s indiglo guages and ever since i filed some of the gauge platform to run the wires it has not been acurate... it started being really bouncy like i would hit 60 in first gear and i would be doing like 20 when i was just crawling up to the light but now (i think i may have just gotten some filings in it) its just high... like 45mph i am going like 50-55 on my spedo (and i think it grows exponentially) when im doing like 75 my spedo says like 85-90 but i have picked up a new cluster, that i would like to do some cool stuff with before i swap it out.
Mine did the same thing so I changed the cable - still did it. :? I went to the J/Y and changed the speedo with a low miles speedo - still did it. :roll: Went to the J/Y a second time and changed the speedo again - still did it. 8O Once again for the third very pissed off time I went to the J/Y and got yet another speedo - it still does it. :evil: I gave up and I no longer care. Each speedo I got bounced a little different so I picked the one that bounces the least and put it in. For some strange reason beond my explaining it has been getting less bouncy everyday. Now it barely does it. On the bright side - I can change a speedo in about eight minutes now. :lol: