Speedo bouncing

I have a 99 Gt with a vortec supercharger, its an automatic,since i put the charger on I have had a few problems the latest is the speedo will bounce around and you can feel the trans shift slightly, I have had the speed sensor changed but that wasent it. any help would be helpful

The only time i've heard of a speedo bouncing is when you go faster than the speedo says.This guy i noe is very crazy and he did that.
Sorry if i am 0 help.

You mean your speedo just kind of flops around all over the place under acceleration? Its probably a stripped speedo gear in the tranny.

Do you have the 3:73 gears? I have yet to put in the Brothers speed calibrator with the stock gear. I have the aftermarket gear in there to compinsate and after about 3 months it gets chewed up and bounces all the time. Change the gear first, then get the calibrator.

yeah i have the same problem my spedo gear was chewd up to but i have not gotten a new one yet. where is a good place to buy those

I used to have a 91 with a speedo that bounced. On mine the problem was a dry speedo cable. I pulled the intsterment cluster out and sprayed wd40 down the exposed end of the cable. So far its work for 4 years.