D_Smith

I recently (three days ago) installed 285/75/r16 (33X11.50) GY duratracs on 16X8 cragar soft 8 wheels w/ 4.5" BS. I have a 2011 Unlimited Sport with a 6 speed manual tranny. Took a trip to go mountain bike in the hill country, and on my drive over there everything was fine ( I had the wind to my back blowing north) Though on my way back (going against the wind) I noticed a giant difference in performance. It topped out at 60 with or with out cruise control if I was in 6th gear. Pedal to the metal just didn't seem to cut it either. Point to all of this is I probably need new gears and to have it tuned for the new tires.
Any suggestions on what gear ratio to go with? Do I need front and rear? Gas mileage went down atleast 8-9 mpg.. Any help to fix the issue would be great.

Thanks,
Daniel

broccoli2

IF you didn't update your computer so it knows you have bigger tires, it is possible it said you were going 60 but you were actually going 65 to 70.
Some of the guys with gear knowledge will chime in soon

KDBinAZ

Running the stock 16 inch rims? Assuming that you are you went from 29 to 33 inch tires (plus over1.5 inches wider) so you will beef to recalibrate the speedo. I'm running 3.21 gears with 32" BFG MT's (255/75/17) and have little issues with using 6 gear. Will have to downshift to 5th (sometimes 4th) on steep grades depending on my configuration, how loaded I am and/or wind

D_Smith

The telling the computer that I have bigger tires sounds plausable. It was just a total let down to see my gas milage plummit like it did. Hopefully I'll find something that works and gets things runnin right again

ZMagic97

Bigger tires do that. In hills and mountains you'll need to hit up 4th or 5th gear for higher speeds.

KDBinAZ

From what I've heard the dealer can only program up to 32" so you will need to buy a programer, plenty to choose from, do a search on the forum. Did you calculate your milage by hand or use the dash computer? If not by hand then this too will he off. Check your actual speed and milage with a GPS to see where your at.

KSRubicon

Generally speaking, regearing isn't even a conversation until you get to 35" tires. Your profile says you have a Sport, but do you know if you have the 3.73 gears or the 3.21...? I'd have to wager that you have the base Sport (3.21) which comes with the 225/75 R16 tire which is 29.29" in diameter. If you move to a 33" tire you're going up 12.7% in diameter and your "real" speed when the speedo says 60 mph is actually 67.63mph. If you know you're running 3.21 gears on 33" tires you might consider the 4.10 gears if you're going to do a gear swap.

KSRubicon

Oh, and getting a progammer is fine, but its just for the speedo reading if you have a stick. A programmer has the added benefit of reprogramming shift points for the guys running auto trans.

matt1608

Depending on the wind, things may have been exaggerated a bit. I was on the interstate the other day going into the wind in my stock x and I had to drop to 5th to go above 60 and the road was flat. Not saying this was what it was, but it's something to think about If nothing else it sounds like a good excuse to get a programmer to give ya some extra power and recalibrate the speedo for the tires

D_Smith

Dang you did your homework... lol. Now I know why it only took me 2&1/2 hours for a trip that was supposed to take almost 4!! I knew the speedo was off but not by that much! A 4:10 gear swap is deffinitely a possibility, The programmer sounds nice but wouldn't it void the computer part of the warranty?