trust96xj

I just put on some 31's not exactly sure what my gearing is, but my speedo is spot on and I don't feel any power being robbed. Any ideas on this? And if anyone knows that's be rad. My jeep is:

96 xj sport
4.0
aw4
4x4
8.25 rear/d35 front (I think)
2" lift
Blah blah blah.
Thanks guys.

NorCalJeep

The AW4 comes with 3.55 gears; unless you got the tow package(which is rare) which comes to 3.73 gears.

Kuro89

Your speedo is off by a percentage, the faster you go the more it's off, also your odometer will be thrown off as well and you'll think your mpg's took a huge dive too
Another thing to think about is the stock tire size for jeeps was tiny, usually around 27"-28" then people often slap on 29" since they fit nicely on a stock jeep and that's where a lot of people start so 29" to 31" is much but it's set up for ~27" from he factory so the increase from stock is about 10% but only 5% from what you previously had, deep breath,
So with 31" @ 25 mph you actual speed is only 27.5mph not generally ticket worthy stuff but at 65 mph your actual speed is 71.5 mph
So Im sorry what was the question?

trust96xj

Speedo is 55mph @55mph. Is it just me or is this Wierd?

Kuro89

How do you know its 55 cop radar?
Long winded edit above ^

TheCK4x4

I have a 4.5 lift and 33s. 93 auto with 3.55gears and when my spedo says I'm going 35 I'm actually going 38. So I can believe it's spot on. My moms 04 Lj has 31s and rides no diff it did stock

Ps: I believe your front axle is a d30, not a d35 lol.

mike mike

Even when new speedos can off by a couple mph and with 20-30 years of wear/use could be worse. And if the devise your using to measure with is off 1 or 2 mph, and if your tires aren't a true measured 31in. and and and.
My AX15, 3.55 gears and 30 tires is off 4-6 mph depending on speed.
Be happy, drive it till it dies!

B_Nichols

When I was on 31's my speedo was perfect through out the whole range. When I put on my 33's........ now its off by like 10 MPH at 65-70 on the speedo.

trust96xj

Yea I checked it on one of those light up signs that tell you your speed. I was just told that they'll mess up your speedo and power and whatnot if you go above anything but stock, but a quarter tanks lasted me over 50 miles all city driving? I don't know I guess 31's aren't as bad as I was told. Thanks for the input guys! I appreciate it.

Kuro89

No they aren't bad at all, I am happy with 31" and stock gearing, but those signs suck and aren't that accurate

VTJeep

I have 235's and my speedo reads a consistent ~2mph slow. Should be spot on when I get the 31's I suppose :|

odgreen

Nope. The bigger tire you get the slower your speedo will read.

VTJeep

Oops... I guess I'll be awaiting a "Newb of The Day" award in the mail.. Thanks for the correction!

VTJeep

And in thinking about.. I suppose that would be the reason it reads slow now..

vlsgmc

What tires did you have before the 31's and did the previous owner make any mods???

Maybe the speedo gear has already been changed in the past.