I'm not sure if I did my math right, but my stock setup was 3.08s. I added 33" tires and 3.55s. If my math is right which isa stretch at times, I'm thinking my speedo should be close to correct. If not,what code should I be using?

 

I've been looking at that chart online but from what I'm reading, it doesn't say anything about great changes and doesn't say anything for 33s.

 

On a 1994 the gear ratio has nothing to do with the speedometer read out.

 

How is that the case? And if so, which code do I use for my truck now?

Does this mean I can change gears any time I want and it won't change the speedo at all?

 

The speed is read as a signal off of the ABS sensor in the rear diff housing, and a tone ring that's bolted to the ring gear. It's based on tire revolutions.

The only time you'd need to change the constant is for a tire size other than what the truck came with from the factory.

 

Got ya. That's simple enough.

 

You need to know your wheel size when it came from the factory so you that you will know the number of teeth of your tone ring.
Example 15" would be 108.
16" would be 120.

Then you would go to the tire makers web site to find the revs per mile of the tires you bought.

Then the math is:
Conversion constant= (Revs per mile) * (number of teeth of tone ring) / 8000

 

The chart shows 8.59 conversion constant. It's that all I need?

 

Assuming you have 33" tires (which I think you do), yes.