Performance mods for the 42RE auto?

[sdjeep]

Well, in a nutshell the auto trans on my '06 Rubicon seems to suck the life out of my engine. I've had other 4.0's all with manual transmissions and they felt way more powerful in everyday driving. Is there anything i can to to change this other than buying a stick? Any kind of mod to get a bit more power to the ground? I have looked into some shift kits, but am a little worried about digging far into the trans itself since it's still under the factory warranty. I love the auto in most situations off road, but on road it's killing me

[jeepboyd]

is the jeep stock? if not you need to regear for the auto as it is shift happy otherwise. i had one in my 99 wj and loved it, my buddy had one in his '03 tj , both jeeps had 32's , and it felt like a dog. you could try a shift kit or one of the performance chips as the tj and the wj are tuned differently from the factory. but i think more gear is going to help the most. let us know what you find out

[OverlandZJ]

Is this the same 42RE which was notorious for failure in the ZJ Grand Cherokee's? Or did they improve it?

[sdjeep]

Is this the same 42RE which was notorious for failure in the ZJ Grand Cherokee's? Or did they improve it?

I believe it is the same basic trans, but they have done some improvements over the years. It's not really prone to failure anymore, just seems to take a lot of power to run it.

As for mods to my Jeep, it is running the stock 245/75/16 Goodyear MTR's with the stock Rubicon 4.10 gears. I was thinking of switching to 4.88's because mileage cant get much worse anyway ( 13-14 mixed) and i plan on going to 255/85/16 when these tires wear out in about another 15,000 miles. That may be a while from now however because money is a bit tight.

Which leads me to another question. Is anybody running that low a gear with only 31's?

[JJonesee]

In my unlimited rubi it really pulls the power away.

I would be interested in the 4.88 swap if you do it.

[sdjeep]

Now I just need to convince the wife it's worth the money . Gears are one thing i really don't feel comfortable trying for myself. Hmmmmm.....this may be harder than I thought.

[PhulesAU]

That metric tire thing kills me, but until you get to the 34 / 35 equivilent I wouldn't go 4.88's. you'll really be turning some rpm's. Mine's an 04 LJ on 35's with 4.88's , and with that combo I only run 150 rpm than stock. It kept me well within the sweet spot. Milage vs. GO!!!

[roadkill]

I have 5.13s and 33s. I turn close to 2750 at 70 mph. while 5.13s sound like too much gear, keep in mind the OD ratio is a .69. with stock 4.10s and 33s 70mph was at 2200 rpm (if I remember right). that is borderline lugging the engine, and is lugging it if you were to try driving under 65 and use the overdrive. getting the cruise rpms back in the 24-2700 rpm range puts it back in the powerband. 4.88s is close to the 4.10 ratio I had stock and from my experiance with the 33s I think that 5.13s are the way to go. you'll be good on 33-35s, nothing worse then to spend money and then realize that you need to regear cause you picked the wrong gear ratio or decided to step up in tire size.

[sdjeep]

I don't mind loosing 1-2 mpg if it will give me better performance. My Jeep only turns maybe 2000-2100 at 65-70 and it does really feel like it is bogging down in OD with the converter locked up. I don't see myself ever going to 35's, but 33's for sure. I do want to re-gear before i get tires and i can't do both at once unfortunatly, so i may just have to compromise with the 4.88's so i can still drive a while on the stockers. 5.13's would be cool though if i could afford to do both at once since i do tow a bit and wouldn't mind the extra bit of grunt

[roadkill]

or you could get the 33s now, switch the OD off in town and on the highway (except for tailwinds, flat, downhill, etc) and save up and regear later. I went about a year before I regeared mine doing just as I said, turn that OD off in town and only using it on the highway when it was beneficial to.