If you go 35's you have to change gears? Is it really that bad stock? 3.8 engine

 

It sucked with mine. Downshifted all the time and I was running KM2s with 4.10s!

 

i got 35" mud grapplers on 4.10 and its fine. i will regear eventually but its not to the point where its a necessity. Downshifts alot but doesnt bother me...

 

I've got 33s with 3.73 gears on the 3.8L. Not much of a noticeable lack of power. AEV procal did wonders as well. I'm looking into 35s in the near future, and I don't intend on regearing. I personally feel you'd be fine based on how 33s feel, but lets hear what others have to say. It also depends on how much you like speed haha.

 

I was running 35's with 3.21's and thought it was bare able until I just regeared to 4.56's now I would say if you have 3.21's definately start saving for a regear as soon as you put on the 35's.

 

No, you don't have to change, but it will suck. You might think it is OK or maybe better than you thought it would be. Then you will regear and wonder what the heck you were thinking!

I am very happy with 4.88 on the '11 Rubicon with a six-speed. It is better than stock gearing and tires.

 

I'm running a 6 spd 3:73 with a Super Chip and it's not bad at all. Cruise 75-80 still no prob Ofcourse the disclaimer of: IN MY OPINION..........

 

Would you mind sharing Rpms at 40 and 75? Assuming you are an auto. Trying to decide between 4.10s and 4.56s.
Sorry- little bit of a thread hijack.

 

It's not that bad stock. A lot of people here like to over dramatize 35's and stock gears. Slight decrease in acceleration from dead stop, after that it's upto the driver. I'm usually always first from the red light and in traffic, just like I was before 35's, and just like I was on different (faster) vehicles. Gears here are not a limitation at all. Mine doesn't downshift like some others said. But I also don't run it in OD. Of course, if you run it in OD, it will suck... and that's driver's fault. I also have a recalibrated speedo. I think some don't, and then they complain. If I regear, it will do pretty much nothing for me. I will not feel any real performance increase... for 2 reasons: 1) it wasn't a real performance degradation to begin with; 2) I will still be running about same or better RPM, except in 1st gear.

 

Gearing can be calculated with a simple math formula.

So with 35's (about 34's for most 35's), 42rle auto tranny:

4.10
3rd gear @40mph: 1621 rpm
OD @75mph: 2097 rpm

4.56
3rd gear @40mph: 1803 rpm
OD @75mph: 2332 rpm

In 3rd gear you'd actually run somewhat higher than indicated above, that's because of the torque converter that comes into play.

I wouldn't do 4.10 for sure, unless you want to run with OD off just as with stock gears. 4.56 is also not enough, your rpm won't be high enough for highway driving. At bare minimum I'd do 4.88, and 5.13 if you have a front D44 or don't wheel much. Currently, I have 3.73 gears, but with OD off, at highway I'm running same rpm as if I had 5.38 gears Can't complain