JK auto issues

[TomCBR]

Hello,

I am new to this site, so I hope this has not been covered before. I did have a look.

I have a 2014 JK 4 door automatic unlimited and love it. Recently I fitted a lift kit from DBOR which is awesome. I also fitted bigger 33 inch Tyers, nothing to big. Last weekend I went for a drive at Yalwal near Nowra and noticed my fuel consumption was through the roof even before I left the main road.

I have now realised that the transmission is not shifting into top gear. Also when I accelerate on the high way to over take for instance it will hold 3rd gear and not shift up until I back right off the gas. It is quite dangerous if your not expecting it. If I manually shit there is no issue.

I did find a forum in the states where someone else had Experienced something similar. Has anyone ocally Experienced this or am I special?

I intend to take it back to the dealer, but would like hear if anyone is aware of this.

Cheers,

Tom

[Paul-JK]

You can get devices such as the Procal that re-program the JK computer to account for the larger tyres. This will mean that your speedo will read correctly again and it should change the shift points in the auto so that they the change at more appropriate times. You'll need to check if this is available for the 2014 model. I have it for mine but mine's a 2010 model (different auto box).

You will notice an increase in fuel consumption from the larger tyres. The size has an affect, as does the extra weight of the larger tyres and the more aggressive tread pattern (assuming you have more aggressive tyres). I put my 33's on at the same times as fitting a 2" lift and all up I had a 1-2l/100km increase depending on the type of driving as was doing. The computer readout for fuel consumption on mine is always wrong though and sometimes by quite a bit so I wouldn't put any great faith in that if I were you. Changing the settings for the new tyre size should make it a little more accurate I think. If you really want to keep an eye on fuel consumption then do it manually.

[TomCBR]

Thanks Paul.

I had a feeling that may be the issue.

I have been doing the fuel calc manually each time I fill up. Last week before I realised the issue my fuel consumption was up around 18-19L per 100.

Thanks again.

[chris0375]

Something isn't right. Even without adjusting for tyre size consumption shouldn't be that bad on the highway. You sure you haven't hit the overdrive button?

[ozjeepster]

Go get a Superchips Flashcal off ebay and program the tyre size up too a 33 and your shift points will return to normal its also a great little code reader that not only tells you the DTC code but what it is , will also change the ratios if you upgrade later on plus a heap of other stuff like disabling the TPMS and you can also download 4 engine runes from Superchips via the Spark software once you register the unit online @ a cost $170 bucks last time i looked at the extra downloads .

OIIIIIIIO

[TomCBR]

Chris,

I'm fairly sure it was due to driving on the high way in 3rd and 4th gear. The road was quite windy and I had the music pumping so I did't notice it. Haha

Thanks ozjeepster, will look into it.

[Paul-JK]

Originally Posted by TomCBR

Thanks Paul.

I had a feeling that may be the issue.

I have been doing the fuel calc manually each time I fill up. Last week before I realised the issue my fuel consumption was up around 18-19L per 100.

Thanks again.

As chris0375 mentioned that sounds high.
It did take mine a long time to loosen up when new. For the first 7000km I couldn't get below 12l/100km even going down a hill with the wind behind me and it was often up in the 13's. Slowly started to loosen up at around 7000km and fuel consumption continued to drop steadily until about 20000km. How many km's does your's have?
Even allowing for that and the the larger tyre's your's does sound high though.