I've got 35" M/T's with a 2.5" lift. Based on that info does anyone have a formula or experience as to how deep I can go? I measured up to the bottom of the grill and it was almost exactly 36". Thanks.

 

ive gone up with water pass my front bumper. Just dont let it get high enough for the intake to suck in and dont shift gears while in water

 

What he said. Additionally, Jeep says 30 inches, so with that configuration I think you'd be okay to 35" inches.

d = 30 + (t - 30)/2 + l

d = depth
t = tire height (inches)
l = suspension lift height

I cannot atest to the accuracy of this formula, but you said you wanted one.

 

Don't forget about your breather lines. Although your jeep may be raised with both a lift and tires, only the increase in tire size will help you out. Your lift does not lift the diff at all and so your breather lines stay at the same height. Although I have not done it, many have extended their breather lines. Just do a search and you'll see.

 

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I believe both diffs have "snorkels" on them that are cliped to the body. I think the front runs up into the engine bay & the rear only runs to the underside of the rear tub. If that is so then a suspension lift would increase thier height above the ground along with the height gained from the change in tire size.