I own a 04 Jeep TJ Wrangler. It has the I-6 and 5 speed tranny. I plan on putting a 3-4 inch suspension lift on it and running 33's. My concern is with my rear axle which is the 35C, Can it handle the tire size? should i re-gear it?. The Truck sees mostly pavement during the week and will be lightly off roaded on the weekends. Im also going to be running a cold air intake to help with gas mileage. Any help here would be greatly appreciated.  

If you limit it to 33 and DO NOT install a replacement locker. the 35c should do okay. I would not go bigger or lock it. Some may tell you its okay but I am a bit conservative and do not try to push limits too much because walking and getting towed stinks and I do not need any trail war/break down stories. On axle ratio, I would regear. At least a 4.10 if mostly street and 4.56 if you live at altitude or in hilly area. BTW, cold air intake is not going to save you any gas and could leave you open to intake water ingestion. I strongly recommend that you leave intake alone.  

Now a snorkel instead of a cold air kit....that would be cool! don't know how they affect performance or mpg's but they sure look goooooood!  

if you had the 6 spd manual you could get by with the 4.10's w/33's..

the 5 spd needs at least a 4.56 to make 5th gear usable. the performance and mileage is extremly poor w. 4.10's and still stinks w/4.56's.  

mudb8-.:
if you had the 6 spd manual you could get by with the 4.10's w/33's..

the 5 spd needs at least a 4.56 to make 5th gear usable. the performance and mileage is extremly poor w. 4.10's and still stinks w/4.56's.

There is not a lot of difference between top gear in 5 speed vs 6 speed and the 6 speed will fair no better in OD than 5 speed with 4.10's  

theres a difference in the OD ratio of the 6spd and the 5... 2100 and 2300 makes a difference w/ the 4.0

.84 6spd vs .73.  

Actually we are both kinda off on this one. OD is .828 on jeep 6 speed and .73 on NV3550 (I was thinking AX15)so there would be 330 RPM difference in cruise RPM in OD at 65 with 33's. So a 4.10 as you suggest would be better with a 6 speed.  

Thanks for replying it really helps. Im not gonna go any bigger then the 33's and not planning on locking the rear. I was just under the impression that the cold air intake would help with mpg even if it wasn't to substantial. I dont think im gonna put a snorkel on it as its my daily driver and drilling a hole in the body kinda makes me cringe. Any ideas on how to help with gas mileage once the lift and tires are on? I knew the vehicle wasnt terribly fuel effecient when i bought it but i wanted a jeep.  

cool, ya found the actual ratio for the nsg..

ya can buy alot of gas for a $300 cold air system...  

There is a lot of misunderstanding about what a cold air intake can and cannot do. As far as MPG, in theory it should be better without it with FI because mixture is controlled regardless of intake temp and warmer air is less dense so there is less pumping losses power wise with warmer air at a cruise. Colder air might give you a extra HP or two WOT but then you run the risk of water ingestion if you play hard in water. If it was me, I would leave stock intake on it.  

a lesson the little boys learned the hard way......



 

I have to point out that a well designed "cold air" kit does more than catch cooler air. a good one such as K&N eliminates restrictions for a more natural air flow. true enough they can make it easier to "take a drink", but a stock box is no set of gills either. My  current truck, an '06 Chevy, is a perfect example. that truck instantly felt more alive just by installing a more open breather. I don't go anywhere near water these days, even with floaties and flippers. I learned the hard way in 1994 the reason the Navy doesnt have trucks. In a hardcore off road rig that might take a dip in the drink, maybe they're not a great plan. but a daily driven truck can benefit. I suppose it all comes down to what this guy will do with his truck. As mudb8's pics clearly illustrate with water that deep it wouldn't matter what ya had yer bobbin' fer apples.  

yep! how do ya like them apples now?.....


 

Im still thinking of running a cold air intake on my jeep as it sees a lot of highway during the week. And when i do get chances to wheel it its usually not very severe (done quite done paying it off yet) so im not to worried about water getting in. Im leaning more towards the banks ram air although its a bit more i like the look of it and it has that nice little shield around it.  

if your really crafty,and unwise with a little extra cash, there are adhesive thermal shields that are heat reflective,or just get some shiny heavy aluminum foil and aome duct tape,wrap that rascal shiney side out,ANY heat kept out of the airstream is good.heck,grab a can of some aluminum paint and spray the intake manifold, just mask off the rest of the engine.