JK sluggish at Highway speeds

[Senoma]

Hello Jeepers, I am new to the forum and new to owning a Jeep.
I bought my Son has a 2011 JK 2 door 3.8 manual with a 2"lift and 32"tyres, runs great, but boy is it slow on the highway! 6th gear is useless unless going down hill, 5th isn't a lot better and it seems you are forever changing gears trying to keep it up with the traffic, with the amount of road trains and idiots on the PDH being slow is dangerous.
I have been searching through the forums looking for suggestions on what I can do to make it safer for him when he's out on the dreaded PDH.
Diff Gearing - change to 4.56 gears?
Fit a Steinbauer [or similar] Chip
Supercharger [not sure how this goes with P plates]
Could the cats be blocked? can these be cut out and replaced with straight pipes, if so what to do with the sensors?
I hope you guys can help

[Thol]

You can spend lots on trying to get more power but balance this against upgrading to something with the 3.6L 2012 onwards. More power 209kw. Maybe not helpfull if your committed to the 2011. Tyres aren't that much oversize otherwise I'd suggest reducing diameter. How much stuff is bolted to it for weight and aerodynamics, roof racks, barwork etc?

[Fishframe]

The Wrangler, aka ‘brick on wheels’ is not known for it’s incredible acceleration.

My 6 speed TJ, 6th is so tall it is hardly usable. 5th ok but without a run up often need to drop back to 4th to overtake at anything under 90 kph.

I drive it more like it’s a small truck than a car. Happy to chug along and not be in a hurry.

[Fishframe]

Senoma, this will interest you -

https://www.jk-forum.com/forums/stoc...seless-177604/

[humdingerslammer]

Originally Posted by Senoma

Hello Jeepers, I am new to the forum and new to owning a Jeep.
I bought my Son has a 2011 JK 2 door 3.8 manual with a 2"lift and 32"tyres, runs great, but boy is it slow on the highway!

I have the 07 JKU Rubicon (4 door) 3.8 Manual also and it does not fly at jet speed. I have learned to live with it. It has done 235000km. The JKU has a 2" lift and 265/70/17 tyres which r slightly bigger than stock.

I have towed a caravan or trailer all over the country, bitumen, dirt off-road etc and typically have the JKU at its maximum weight. I have no trouble keeping in 6th gear on the flat. I usually sit on 90 - 100k/hr. Go back to 5th when up a hill and sometimes down to 4th/3rd. All this is standard for a manual: u do have to work the gears....it's not an automatic. Also, it's not a Ferrari!! so don't drive it like u expect it to be.

Given that your vehicle is used/second hand, I suggest changing the plugs and plug leads as it is important that these r in top condition. Don't use the long life ones... not necessary and anyway they don't last as long as they say, in my experience. I usually get 60000km on the clock when I change the plugs and leads... do them both since they r relatively cheap items and preventative maintenance is always a good mantra. Also change air filter and oil and oil filter (I use 5/40 recommended or 10/40 (synthetic or semisynthetic is best).

Things like bullbar/roofracks etc add to deadweight and wind resistance so if u don't need the roof rack on, take it off. Unlikely that a Steinbauer will make much different (aren't these 4 diesels). If u still want an engine, don't fit a supercharger! Unlikely that the cats r blocked but u might want to change the oxygen sensors and the EGR valve and the PCR valve.

I assume PDH means Peninsular Development Highway going up the centre of Cape York. Why the hell would u want to drive fast on that "highway" if this is the one to which u refer?

Hope all this helps.

[Senoma]

I assume PDH means Peninsular Development Highway going up the centre of Cape York. Why the hell would u want to drive fast on that "highway" if this is the one to which u refer?

Hope all this helps.[/QUOTE]

Cheers for the advice, I have changed plugs and leads, also the throttle body and there is no roofrack on it just a small steel bumper replacement type bullbar.

and the PDH is the Peak Downs Highway

[Banshee]

I have a 2008 3.8 manual, and you're not wrong about the top gears! When I got it, the cruise control couldn't hold speed at 110 or 100 on the slight hills on the M4 west of Sydney and I was constantly going down to 4th to keep it at speed.

These days, I'll just set it to 100 instead. Replaced plugs & leads as well, and I could never tell any difference with the tuners. (I got one because I found I was pinging a lot going up the Blue Mountains, where I live. The best fix to reduce that was an AEV snorkle that dropped my inlet temps significantly. ~5-15C over ambient now, depending on engine speed.)

Interestingly, I don't seem to have the same issue now with the RIPP Long Tube Headers. I didn't get them for power, but because they were not significantly more expensive than getting the Y pipe with cats from CJD would have been, when I had a cat failure. They're a bit noisy with the RIPP full system and the roof off & tube doors on, I will likely replace or add another muffler if I get the spare cash...