Armydad

Hi all,

I have a 98 GT that i will be putting 3.73 gears in. They dont have the proper tranny speedo gear for those rear gears, I think there is a small box unit sold somewhere that needs to be installed to correct the speedo. What will the mph difference be from the stock gears to the 3.73's, I may just run them and do the math while I drive.

lizzyfan

Mine were off about 20 MPH and then I got a Speedcal that you are talking bout

eventer289

Yes, it's called a Dallas Mustang Speedcal. They are very simple to install, and the unit just splices in between the tranny and the gauge cluster. Based on your gears, you just push certain sliding switches on the inside in a particular sequence and it re calibrates the signal. All you have to do is splice into a powered line. I just spliced into the cigarette lighter power cord.

Armydad

Thanks guys,
Damn 20mph is more than I thought it would be, looks like I'll be ordering the magic box,
thanks for the install rundown eventer, sounds easy enough, where did you mount it, I think they reccomend under the center console by the shifter.

lizzyfan

Yea, it's under the console in front of the shifter, fits fine and does not move around

Armydad

Thanks, already found it @ A Muscle, $99.00. What is the stock GT ratio, 3.27?

tbirdscwd

Yup, 3.27:1 is the stock rear gear. I think 2.73:1 on autos, but could be wrong. But I run the SpeedCal and it's very easy to install and adjust for changes.

Here's a calculator that will show you how fast in each gear you will go and you can adjust tire sizes, gear ratios, and transmission. Thanks Cliffyk

http://www.paladinmicro.com/PalMFrame00.htm?wks=spd