Just another Speedo Gear post

[Judhudson]

Ok, my speedometer reads 10 mph faster than what I am going.  This is because I changed the wheels/rim size.  I'm trying to figure out the correct Speedo Gear I need to get.

I am following this chart:
http://www.mymopar.com/speedometer.htm

My Tire Size is 235/60/15 and the wheels I am running are 15x7 Vectors all around.

So by my calculations (if I am right) are:

235mm/25.4mm = 9.25" Section Width
9.25 x 60% = 5.55" Side Wall Thickness
5.55 x 2 = 11.1" Total Side Wall Height
11.1 + 15 = 26.1" Diameter

So I fall under the 26" Overall Tire Diameter.  Good.  Now here is where I am stuck at.  I don't know my Axel Ratio or even how to tell what rear-end I have!  Anybody have an idea if 73 Chargers SE with a 400 BB 4 Barrel shares the same rear end?

Also, is changing the speedo gear a difficult process or is it a piece of cake?

[Ghoste]

Changing the speedo gear is easy but first you'll need that ratio.  Lift the back of the car and turn the wheels and count the number of revolutions of the driveshaft to one revolution of the wheel.  It's crude, but it'll get you in the park.

[Chryco Psycho]

you will lose fluid but it is easy to change the gear