34 inch tires with 3.73s

[Snzzbry_Ovrlnd]

Ok guys. I have 295/70-R18s on my JTO, and even after calibrating with my Tazer, it still doesn't want to go into 8. I find it in 6 or 7 most of the time, even at 74mph. What speed does your transmission shift into 8 at? @Armyman247 @Georgia Jeeper

Lin

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[Georgia Jeeper]

Edit—-you did the 2.5 leveling? Usually when I hear leveling kit for the JT my mind goes to the Teraflex 1.5.
[/QUOTE]

Yep. I did this Rough Country 2.5" leveling kit. Overall I am happy with the quality of it, and the ease of install.

 

[Tufelhundin]

Ok guys. I have 295/70-R18s on my JTO, and even after calibrating with my Tazer, it still doesn't want to go into 8. I find it in 6 or 7 most of the time, even at 74mph. What speed does your transmission shift into 8 at? @Armyman247 @Georgia Jeeper

Lin

Quick question, do you also get crap mileage?

Just curious...

For if it does then it sure sounds like some do well and some do not “mine”

 

[Georgia Jeeper]

@Snzzbry_Ovrlnd mine goes into 8th cruising down the highway as long as it is flat. If it is flat it will run in 8th anywhere from 70 to 80 MPH. I have found though, that any slight incline knocks it back down to 7th. It typically goes back and forth between 7th and 8th, and I only drop down to 6th if I'm pulling a big hill or really get on it.

 

[jjdustr340]

Ok guys. I have 295/70-R18s on my JTO, and even after calibrating with my Tazer, it still doesn't want to go into 8. I find it in 6 or 7 most of the time, even at 74mph. What speed does your transmission shift into 8 at? @Armyman247 @Georgia Jeeper

Lin

Did you actually measure the height of the tires and plug that in?
Most tires are not actually the height listed and if you plug that number in with a programmer, it still won’t be correct.
I had 315/70/17 on my JKU which is supposed to be 34.4 inches tall. Mounted on a 9 inch wide rim, under weight and inflated to 30 psi, they PHYSICALLY measured 33.25. Once I plugged that number into the calibration the speedo was dead on and shifting issues went away.

295/70/18 shows as 34.3 inches diameter. I’d guess when you measure it you’ll find it closer to 33.5 maybe.
There’s 2 different schools of thought in the measuring of the tire. One is to measure all the way across from ground to top.
The other is measure from ground to center of wheel then multiply by two.
Im not going into which is better/right/preferred here. That’s for another day.

 

[Snzzbry_Ovrlnd]

Did you actually measure the height of the tires and plug that in?
Most tires are not actually the height listed and if you plug that number in with a programmer, it still won’t be correct.
I had 315/70/17 on my JKU which is supposed to be 34.4 inches tall. Mounted on a 9 inch wide rim, under weight and inflated to 30 psi, they PHYSICALLY measured 33.25. Once I plugged that number into the calibration the speedo was dead on and shifting issues went away.

295/70/18 shows as 34.3 inches diameter. I’d guess when you measure it you’ll find it closer to 33.5 maybe.
There’s 2 different schools of thought in the measuring of the tire. One is to measure all the way across from ground to top.
The other is measure from ground to center of wheel then multiply by two.
Im not going into which is better/right/preferred here. That’s for another day.

JJ,
I'm going to measure them this morning. They are currently on stock rims at 39/40 psi.

 

[Snzzbry_Ovrlnd]

JJ,
I'm going to measure them this morning. They are currently on stock rims at 39/40 psi.

My tires were 33.3 inches on full load. I've changed the Tazer. I didn't get up to highway speeds yesterday but when I do I'll post if it shifts into 8. Thanks for the hint to use the exact measurement and not the advertised height.

Lin.

 

[jjdustr340]

My tires were 33.3 inches on full load. I've changed the Tazer. I didn't get up to highway speeds yesterday but when I do I'll post if it shifts into 8. Thanks for the hint to use the exact measurement and not the advertised height.

Lin.

Absolutely. It should be much better now. Even with the measurements, sometimes you need to compare the speed shown to a gps or gps app and adjust again. However, changing to the measurement you got should get you really close. Let me know how it goes!

 

[Tufelhundin]

My tires are 315/70-17 and I had to go to 33.25 to get the gps and speedometer to match up as well.

 

[Snzzbry_Ovrlnd]

Absolutely. It should be much better now. Even with the measurements, sometimes you need to compare the speed shown to a gps or gps app and adjust again. However, changing to the measurement you got should get you really close. Let me know how it goes!

I was up to 60mph and it naturally changed to 8. I call that a success.

 

[tysongladiator]

Ran my JT on 34s and then 35s on the 3.73s for over 65,000 miles before I regeared. Towed a camper, boat, and ATVs with it and wheeled with it. You'll be fine.

 

[JerseyMike]

I'm currently on 315/70/17 (35's) and with stock 3.73 and auto. It honestly feels ok after programing with Jscan but when I display the gears I do see that I am rarely in 8th (has to be perfectly flat with slight decline or no incline). II thought long and hard and partly because there is a great gear shop near me (Globex that did gears in a mustang for me and my brothers JL) I am getting 4.88 put in next week. At first I regretted not getting a max tow but now I am happy as that money can go towards more aggressive gearing. It will cost me a bit more in the end (not that much as Globex has great pricing) but from what I have heard it will give a great performance bump and I can go 37's down the road if I choose.

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