hmm... my speedo bounces sometimes... i got a 89 toyota that had a 3.0 5speed and now its got the 3.4.. its always done it though... sometimes it will start bouncing way faster than normal and then go all the way to 110mph... shut the truck off and crank it back up and that fixes it sometimes... and sometimes it just fixes itself.. been doin it for about 3 years now... i havent fooled with it but now im thinkin about it