Chevrolet Silverado rear end gear ration problem
 

I have a full size Chevy silverado. I put low profile 17’s on it and now the speedo is about the mph off. when I am going 45 the speedo says 55. I would like to change the ring and pinion gear to make up for it because the rear end is already making a noise. not low on fluid though. I don’t know what the stock ratio is or how to tell. but can someone tell me how the ratio’s work. do I need a higher or lower gear ratio.

Keep the stock ratio gear and get the computer programmed for the tires? Much cheaper

It's way easier to add or subtract a few mph on the spedo and will cost a ton less also.

thanks for your advice.. trying to do it, hopefully my trouble will gone :D . Thanks dude..