Question...How to determine rear end gearing

How can I find out what rear end gearing I have? I need to determine what I have and see if it needs to change based on my wheel size. I am running 35x12.50s on 18 inch rims. What gear ratio would be best?

Thanks for any input...

 

Is there anyone that can answer this? I know there has to be someone. HELP!

 

There should be a tag on your diffs indicating your ratio .
As far as deciding what ratio to go with , it all depends on what you plan to do with the truck .
If you prefer plenty of power and torque off the line , a higher gear ratio is better .
If you prefer fuel economy on the highway , a lower gear ratio is better .

 

You have 3.73's. All of the V6's do.

Since you are an auto, I will recommend going to 4.56's or 4.88's. Looking at your mods I take it you like power so I would get the 4.88's. I am running 4.88's on 33" tires and I love my 4.88's. I run about 2700rpm at 75mph on the HWY and it hardly affected my fuel economy at all and the road noise is still louder than the engine. With 35's you would run about 2550rpm at 75mph.