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
Performance mods for the 42RE auto?
- Thread starter sdjeep
- Start date
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
Expedition Leader
Is this the same 42RE which was notorious for failure in the ZJ Grand Cherokee's? Or did they improve it?
OverlandXJ said:
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?
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PhulesAU
Explorer
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
Adventurer
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.
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:smiley_drive:
roadkill
Adventurer
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.
Hmmm, that could be an option also. I take it you did lose a bit of power even with the OD off around town though? How bad was it? My problem is money seems to have a way of burning through my pocket and falling into my wifes open hands to pay bills
Otherwise I would try to just do them both at once. If i do go with the 5.13's and 33's, is a 1-2 mpg loss about right, or is it more? I'm getting about 13-14 with a highway best of almost 17.
Otherwise I would try to just do them both at once. If i do go with the 5.13's and 33's, is a 1-2 mpg loss about right, or is it more? I'm getting about 13-14 with a highway best of almost 17.
roadkill
Adventurer
you'll loose a little but its not too bad. mostly noticable at hwy speeds (and in od) I get 11.5-13.5 in town and got as good as 14.8 on a road trip recently (loaded down heavy and 70-75 mph in on the way to Big Bend). I know I can probably do a little better if I slowed down and lightened up my rig. winch, bumpers, tools, hi lift, skids and armor all adds up.
C-Fish
Adventurer
roadkill said:
That is exactly how I drive my WJ.
2003 WJ 42Re
285/75/16 (33" equivalent)
ARB bumper, Winch, Rear tire carrier bumper=heavy to an already hefty rig.
I want to regear, but I'll loose the ARB in the front due to the carrier break (3.54 and lower). This adds more to the cost, so I've chosen the live with it for now and not use OD unless on flat or downhill grades. I am seeing 15.5mpg combined (using the computer readout), with highway miles being 75/25.
I will say that those of you running roof racks might want to evaluate their use to you. I ran one on the WJ for the first few weeks of ownership and my mileage was only 13.7 combined (same highway/city ratio).
I took it off and gained almost 2mpg + I lost the weight associated with it.
I do tow a bit with my LJ, so the 5.13's would be nice for that if i get the tires first. But if i get the tires first, my towing performance will suffer untill i get the gears so i should go with the 4.88's first. But if i go with the 4.88's first, then i can't go to 5.13's when i get the tires! AHHHHHH! It's a viscious circle!
roadkill
Adventurer
what do you tow? I pulled my M416 with up to 1000lbs in it with stock gears and 33s. I suffered on the hwy a bit but around town I was fine, the key is keep that OD turned off when pulling. I can now leave it on while towing. it has good power and I have yet to have the tranny hunt for gears while towing.