Larger tires

[RELBUS]

Thanks! Mopar 2" lift. I've noticed I only get in 8th at around 80mph when perfectly flat with the cruise on. If I so much as spot a hill in the distance the Jeep drops a gear. Its not bad power wise at all, its just not good as it was.

I probably expect too much out of 8th. I am used to my cummins ram that will hold the top gear pulling my TJ on a trailer at 80mph up a mountain pass.
I will say, I love how the Jeep displays the current gear next to D in the cluster. Pretty slick, FCA cluster and infotainment just keeps getting better.

Sponsored

 

[aug0211]

Thanks! Mopar 2" lift. I've noticed I only get in 8th at around 80mph when perfectly flat with the cruise on. If I so much as spot a hill in the distance the Jeep drops a gear. Its not bad power wise at all, its just not good as it was.

I probably expect too much out of 8th. I am used to my cummins ram that will hold the top gear pulling my TJ on a trailer at 80mph up a mountain pass.
I will say, I love how the Jeep displays the current gear next to D in the cluster. Pretty slick, FCA cluster and infotainment just keeps getting better.

We are definitely having different experiences with 8th. Do you have your rig programmed for your larger tires? Maybe that's the difference.

I'm hitting 8th regularly and I don't need to hit 80 MPH to get into 8th.

I will check on the way home, but on flat roads I bet I hit 8th once I am holding steady around 65-70 MPH. I then drop in to 7th if I decide to accelerate up to 75 for instance- but as soon as I stop accelerating and hold steady at 75, I'm right back in to 8th. It's basically the "highway cruise" gear for me - no acceleration, but is used all the time to maintain normal highway speed.

 

[RELBUS]

Yep, Jeep is programmed with Tazer Lite for 37's. I confirmed using speedbox app on my iphone that speedo is accurate.

I will pay closer attention on the way home from work, but so far it seems like its rarely in 8th. I am rarely using the cruise too in my commute so that may have something to do with it. Im flying in Chicago rush hour traffic on I80. I will add that stock it didn't seem like it took much for the Jeep to want to drop a gear from 8th.

Again - I am coming from 500+hp diesel pickup that NEVER downshifts at highway speeds

 

[aug0211]

Yep, Jeep is programmed with Tazer Lite for 37's. I confirmed using speedbox app on my iphone that speedo is accurate.

I will pay closer attention on the way home from work, but so far it seems like its rarely in 8th. I am rarely using the cruise too in my commute so that may have something to do with it. Im flying in Chicago rush hour traffic on I80. I will add that stock it didn't seem like it took much for the Jeep to want to drop a gear from 8th.

Again - I am coming from 500+hp diesel pickup that NEVER downshifts at highway speeds

Interesting! Do you remember what size you have programmed in your TazerJL? I actually just played with mine a bit, so I may have thrown things off for my drive home. We'll see.

I have been comparing my speed to the speed in the Waze GPS app - I will have to compare to SpeedBox as well.

 

[RELBUS]

37.063 or something like that was the closest to 37" I could get. I assume waze and speedbox are both using the same GPS data to display speed, although I did not try waze for comparison

 

[RELBUS]

Ok- I hit 8th around 58-60 and can hold it until 70 ish. From 70-79 it doesn’t want to hold or shift into 8th. At 80 it will go into 8th but downshifts at the thought of an incline.

I’ve only got roughly 200 miles with the 37’s. On my commute home I’d set the cruise and bump it up a few mph at a time and then wait to see if it would shift into 8th or not
Starting at 57mph and working my way up to 83mph.

 

[aug0211]

37.063 or something like that was the closest to 37" I could get. I assume waze and speedbox are both using the same GPS data to display speed, although I did not try waze for comparison

One note here - TazerJL runs off of actual tire size, not "advertised" size. So, you want to measure your tires to see what their actual height is under load, and get the closest number the TazerJL offers to your actual measurement. My guess is it will be slightly below 37", but it could also turn out to be exactly what you have I am still playing with mine to get as precise as possible based on vehicle reported speed and GPS app speeds. Also, you were correct - Waze and the other app match 100%. I learned something fun - if I plug my phone in to CarPlay, the vehicle forces the GPS apps on the phone to use the vehicle speed! So interesting! So, when I have Waze open, it might be 3 MPH off from the vehicle reported speed - then if I plug my phone in, the Waze speed miraculously changes to match the vehicle 100%. Lesson learned.... do not try to "match" speeds with the phone plugged in, make sure it's disconnected (Bluetooth connection seems to be fine).

Ok- I hit 8th around 58-60 and can hold it until 70 ish. From 70-79 it doesn’t want to hold or shift into 8th. At 80 it will go into 8th but downshifts at the thought of an incline.

I’ve only got roughly 200 miles with the 37’s. On my commute home I’d set the cruise and bump it up a few mph at a time and then wait to see if it would shift into 8th or not
Starting at 57mph and working my way up to 83mph.

I tested on my way in and I was in 8th at 55 MPH when cruising. I will note - if you're slowly creeping up a few MPH at a time, I wouldn't expect to hit 8th while you're creeping up. I think you already know that, though. I can see it having a tough time holding 80 MPH in 8th gear - that seems fair to me, I guess - there is a bit of power required to keep the brick moving at 80 MPH with all of the rolling resistance we have on our tires and wind resistance we have in our elegant metal slabs

 

[RELBUS]

Yep, I figured it was actual tire size. I'm happy with how accurate it is, prob wont bother measuring. This sure beats speedo gear changes, and the dakota digital signal interface used to correct the speedo on my TJ!

Interesting on the carplay changing the speed in the app to match the dash. I need to experiment with this. I honestly can't recall if I was plugged in when I used speedbox or not. Now you have my questioning my earlier results.

I am running an errand here shortly and intend to double check

 

[coukos34]

Finally got my wheels and tires on.
Quadratec 41 17x8.5” wheels with +10 offset
BFG AT KO2 315/70r17

 

[Daniwood]

I put 35's the day I got it and have not noticed any problem, mine is the 2.0 turbo, they are Nitto Trail Grapplers 35x12.5x17, I took them off my 2017 Rubicon.

 

[Uhdinator]

Sport = 3:45 ratio
Sport S/Sahara = 3:73
Rubicon = 4:10

Probably a good idea to mention what gear ratio you have if stating 37's are fine.
37's probably fine with 3:73 as well if you only go to the mall.
37's most likely not a big deal for a Rubicon.

I wouldn't put 37's on my Sport 2 dr HT with 3:45 axle ratio. It does fine with 32-33" and doesn't feel gutless with an 8 speed and has been re calibrated, and gets 25-26 mpg. The re cal was done wrong by the dealer at 34," I measured at 32" even though the mfg says they are 32.7 (likely maybe at 65PSI) I run at 30 PSI. Dealer evidently guessed at tire size and speedo was off 7mph.
Just saying.........results may vary depending on Axle ratio, intended use, transmission type, and Speedo calibration, 4 dr vs 2 dr.

35's might be fine on a Sport 2 dr soft top with 3:45 axles and auto, but be a dog on a 4 dr Sport, manual with HT, Steel bumpers, Winch, skid plates, added armor etc.

 

[Huehue80]

I have experienced the same as you on my turbo JLUR. I barely see 8th. I thinking a regear would fix this. What gear ratio were you thinking. I was thinking 4.88 so if I want to run 40's I won't have to regear in the future. When I did the calculation to get back to factory spec it was between 4.56 and 4.88.

37x12.5r17
3.5 metalcloak game changer lift with Rocksport long travel shocks.

Rides smooth as stock

View attachment 102460

 

[GARRIGA]

Guys going 80 on 37. What mpg are you seeing on a flat road on instant? If you don’t mind.

Sponsored