The speedo (and odometer) in my 87 LS is showing about 12mph lower than I'm actually going. Need to change the speedo drive gear, but don't know which I need (or which one I have).
I've searched a little on the net with few results. The problem is that I'm not exactly sure what to search for.
Do any of you guys have any knowledge of such things?

Thanks in advance.

 

Question...what size tires are you running out back?

 

I've got winter tires on now, they are 195 75/14. The summer tires are 265 50/15. I think they have the same circumference. It's an automatic transmission, three gears and overdrive.

 

http://www.tciauto.com/Products/Tech...eedo_gears.asp

it sounds like you need to change your spedo gears. look at this chart and put your info
and it will tell you what gears to get.

 

Thanks for the link.
What's the difference between drive teeth and driven teeth? And how do I know how many teeth to put in?

 

there is a gear on the output shaft of the trans.(the drive gear) and there is a gear on the speedo cable(the driven gear)
you may have to get them both.