285/70/17 on stock JL Willy 2021 problems?

[Willywong]

I noticed hardly any difference at all going from LT255/75R17 Destination MT2’s to the LT285/70R17 KO2’s.

I guess I’m the one in a million because that’s what I read too but no my car is struggling to shift to 8th gear

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[Willywong]

There is a lot of discussion about tires and gearing and 8th gear. A lot of people do report trouble with 8th gear running larger tires.
I have a 2018 JLU Sport V6 8-speed. I put on Rubicon takeoff tires, they fit ok, no problems with the fit or the ride, but there were a lot of situations where I couldn't maintain 8th gear anymore. On the freeway at the speed limit, level ground, I could normally maintain 8th gear but any little incline or headwind and it would drop to 7th gear. I didn't really notice any changes to acceleration, it still seems to drive the same as it did before.
It is what it is, running that tire size was/is important to me for what I use the Jeep for so I have to put up with 7th gear sometimes. I also added Rubicon springs and shocks and new Mopar lower control arms. It's a little taller but it still pretty much rides the same way.

I’m probably getting the superchips to let the computer know what tire size I’m running hopefully that works

 

[drrobinson]

Yesterday I put 285/75/17 Falken Wildpeaks on my 2021 Willys with stock wheels and a 1.75" wheel spacer. And I ordered a Superchips product today so that the tire size can be recalibrated. However even with my larger tires than yours, I am still able to get into 8th gear no problem even before the computer adjustment. I have the 2.0T.

I’m considering a similar setup. Just out of curiosity, why the wheel spacer?

 

[Willywong]

Yeah, you'll probably want to buy a Tazer or Superchips product to adjust the tire size settings. Not telling the computer that you have larger diameter tires is likely to cause several of the issues you are reporting.

Yesterday I put 285/75/17 Falken Wildpeaks on my 2021 Willys with stock wheels and a 1.75" wheel spacer. And I ordered a Superchips product today so that the tire size can be recalibrated. However even with my larger tires than yours, I am still able to get into 8th gear no problem even before the computer adjustment. I have the 2.0T.

did you have issues in 8th gear or anything similar to that. Would the superchips correct the issue of the car not shifting to 8th?

 

[@DesertRubi]

I’m considering a similar setup. Just out of curiosity, why the wheel spacer?

I wanted a little bit of tire poke without having to give up my Willys wheels. And I wasn't sure if the 34" tires would rub without the spacers. There's plenty of clearance with the spacers installed. Tomorrow I'm installing a Teraflex 1.5" spring spacer kit.

 

[@DesertRubi]

did you have issues in 8th gear or anything similar to that. Would the superchips correct the issue of the car not shifting to 8th?

I don't have any issues in 8th gear. The only changes I notice so far are that the ride is more stable and it takes a bit more to bring the Jeep to a stop. I believe part of the reason of recalibrating the tire size has to do with the computer interpreting when to shift, so maybe that would help. There are a lot of messages in the forums about needing to recalibrate the speedo and tire size when installing bigger tires/lift.

 

[Willywong]

I don't have any issues in 8th gear. The only changes I notice so far are that the ride is more stable and it takes a bit more to bring the Jeep to a stop. I believe part of the reason of recalibrating the tire size has to do with the computer interpreting when to shift, so maybe that would help. There are a lot of messages in the forums about needing to recalibrate the speedo and tire size when installing bigger tires/lift.

Thanks man I guess I’ll have to give that a try and fingers crossed that works!

 

[azwjowner]

It could also just be the new tires and the feeling disappears after 200 miles. Every time I buy a brand new set of tires they feel softer and harder to turn until they break in. Last time I went up 0.5" with new tires it felt oddly sluggish but that went away as the tires settled in.

 

[Willywong]

It could also just be the new tires and the feeling disappears after 200 miles. Every time I buy a brand new set of tires they feel softer and harder to turn until they break in. Last time I went up 0.5" with new tires it felt oddly sluggish but that went away as the tires settled in.

You think that would have an impact on what its doing to my transmission?

 

[Zandcwhite]

Do you know if this gear shifting etc. factor be the same with the diesel powertrain?

The diesel makes so much torque it still drives and shifts fine on 37's. You'll need to correct for tire size, but no need for a tune.

 

[azwjowner]

You think that would have an impact on what its doing to my transmission?

My experience was on a 4-speed, so hard to say. If it were me, I'd drive 250 miles and see how it felt. I always have a brief drop in MPG with new tires, meaning that the rolling resistance is higher, which puts more effort on the transmission. So maybe. The transmission might also adapt over time as well.

 

[blnewt]

I run slightly larger 295/70/17s on my 19 2dr w/ V6 & 8AT. 8th speed kicks in, but mainly when I'm running on the flat, slightly downhill, or with a tailwind. I have the Tazer Lite, and it helps w/ the shift points and seems to get a bit better mpg than prior to adding the Tazer. I have some 315/70/17s waiting in my shed to install soon. I'd imagine 8th gear will just be for show or if I manually shift it.

@Willywong I'd consider adding Rubicon springs to your Willys (you already have the Rubicon shocks) and the longer Mopar lift LCAs, this will give you decent clearance for those larger tires, uses Mopar parts, typically won't cost much, and the longer LCAs will make your Jeep track great at hwy speeds. You could get a takeoff set on the site for $200 or less and have an extra set of shocks.
Here's my install thread on them, and post #4 for the LCA install.
https://www.jlwranglerforums.com/forum/threads/rubicon-suspension-on-2-door-sport.40700/

 

[Willywong]

I run slightly larger 295/70/17s on my 19 2dr w/ V6 & 8AT. 8th speed kicks in, but mainly when I'm running on the flat, slightly downhill, or with a tailwind. I have the Tazer Lite, and it helps w/ the shift points and seems to get a bit better mpg than prior to adding the Tazer. I have some 315/70/17s waiting in my shed to install soon. I'd imagine 8th gear will just be for show or if I manually shift it.

@Willywong I'd consider adding Rubicon springs to your Willys (you already have the Rubicon shocks) and the longer Mopar lift LCAs, this will give you decent clearance for those larger tires, uses Mopar parts, typically won't cost much, and the longer LCAs will make your Jeep track great at hwy speeds. You could get a takeoff set on the site for $200 or less and have an extra set of shocks.
Here's my install thread on them, and post #4 for the LCA install.
https://www.jlwranglerforums.com/forum/threads/rubicon-suspension-on-2-door-sport.40700/

Thanks that was really well written and step by step. So after you installed your tazer your Jeep still wasn’t switching to 8th? I was hoping on getting the superchips to hopefully address the issue. You think it’ll do anything? I’ll definitely be looking for some springs

 

[Mudduck]

I’m still on stock Willys KM2s, no lift yet and i dont get into 8th unless its downhill or flat with a tailwind.

 

[Willywong]

I’m still on stock Willys KM2s, no lift yet and i dont get into 8th unless its downhill or flat with a tailwind.

you’re with the stock Willy tires 255/75/17? And you don’t go into 8th? When I had those my car would go into 8th on highways or when I’m flooring it on the streets.

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