Bigger lift and tires, struggling Trasmission

[rporter325]

Have a 2019 JLUR 2.0 auto 8 and took a road trip to Savannah from Atlanta this week. I kept finding that as I would try to accelerate over 70 uphill, I would have to drop down to fourth before I can start gaining forward momentum. Couldn’t get to 80 uphill, only flat and downhill. I just lifted my jeep 3 inches and put 37 inch trail grapplers on it prior to the trip. Just seems that 70 mph uphill makes it struggle (Has to drop to 4th and 5k rpm with full pedal). Are the issues I’m having common with not regearing from the 4.10? It still runs great in the city on low end torque, even gets up to 70 right quick on flat ground. A buddy of mine told me that it shouldn’t struggle like that. I’ve already had major headaches with FCA after wheeling it and sucking water into the transmission. Replaced it with a brand new transmission, heater, and cooler from FCA (All out of pocket $7k later) and haven’t been off Road since. Just recently upgraded tires and lift. I’m terrified to take it back after they raked me over the coals last time. Any help on this would be appreciated.

Ps. I only hit 8th gear once on this trip

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[txj2go]

People have reported problems with 33" tires and 3.45 gears. 37" tires with 4.10 gears is actually lower effective ratio than 33" tires on a sport s. However I take it that a lot of people do regear when they go beyond 35" tires.

 

[The Last Cowboy]

Go with 4.30 or 4.56 gears to make up for the size difference. Also make sure you reprogrammed your speedo. 70 indicated could actually be over 80. Use an app like Speedbox to check your actual speed. Just reprogramming the speedo will make it shift much better.

 

[txj2go]

70 indicated could actually be over 80.

Here is the approximate math- on a Rubi going from 33" tires to 37" tires would put you at actual 78.5 mph at indicated 70. Of course this is approximate because 33" tires likely aren't exactly 33 and 37" tires might not be exactly 37 either.

 

[ThirtyOne]

For 37s most guys I know who re-gear are going to 4.88 or 5.13.

 

[oceanblue2019]

Have a 2019 JLUR 2.0 auto 8 and took a road trip to Savannah from Atlanta this week. I kept finding that as I would try to accelerate over 70 uphill, I would have to drop down to fourth before I can start gaining forward momentum. Couldn’t get to 80 uphill, only flat and downhill. I just lifted my jeep 3 inches and put 37 inch trail grapplers on it prior to the trip. Just seems that 70 mph uphill makes it struggle (Has to drop to 4th and 5k rpm with full pedal). Are the issues I’m having common with not regearing from the 4.10? It still runs great in the city on low end torque, even gets up to 70 right quick on flat ground. A buddy of mine told me that it shouldn’t struggle like that. I’ve already had major headaches with FCA after wheeling it and sucking water into the transmission. Replaced it with a brand new transmission, heater, and cooler from FCA (All out of pocket $7k later) and haven’t been off Road since. Just recently upgraded tires and lift. I’m terrified to take it back after they raked me over the coals last time. Any help on this would be appreciated.

Ps. I only hit 8th gear once on this trip

You need to re-gear. I actually don't like how mine drives with 35's with the stock 4.10's and have no idea how someone could tolerate bigger.

Also make sure the computer is re-programmed for your tire size and gear ratio if you change it.

 

[limeade]

Have a 2019 JLUR 2.0 auto 8 and took a road trip to Savannah from Atlanta this week. I kept finding that as I would try to accelerate over 70 uphill, I would have to drop down to fourth before I can start gaining forward momentum. Couldn’t get to 80 uphill, only flat and downhill. I just lifted my jeep 3 inches and put 37 inch trail grapplers on it prior to the trip. Just seems that 70 mph uphill makes it struggle (Has to drop to 4th and 5k rpm with full pedal). Are the issues I’m having common with not regearing from the 4.10? It still runs great in the city on low end torque, even gets up to 70 right quick on flat ground. A buddy of mine told me that it shouldn’t struggle like that. I’ve already had major headaches with FCA after wheeling it and sucking water into the transmission. Replaced it with a brand new transmission, heater, and cooler from FCA (All out of pocket $7k later) and haven’t been off Road since. Just recently upgraded tires and lift. I’m terrified to take it back after they raked me over the coals last time. Any help on this would be appreciated.

Ps. I only hit 8th gear once on this trip

I too have a 2.0 w/8 Spd auto, 37" tires, and 4.10 gears. I live in a very mountainous area of Northern Nevada with very few flat roads. I drive my JLUR in the mountains very frequently. I live at 5,200' above SL and drive in mountains 9k+ ASL. With my current setup, I can drive 80+ mph up mountain grades, passing slower cars if needed, and not have the pedal floored the whole time. When I do this, it will sometimes drop down to 4th on the steeper sections, but usually will be in 5th. If I'm taking it easy and driving the speed limit, the trans will be in 6th going uphill a lot of the time.

Here's an example: When I drive from Reno to Sacramento, CA on I-80, there's a section called Donner Pass. It's a fairly long (couple miles) grade beginning around 5,500' ASL and goes to about 8,400'ASL. Semi-trucks are only going about 25-35mph and most passenger cars are 65 mph or less. I can comfortably drive that grade at 85-90 mph (4th and 5th gear) without the pedal floored the whole time.

My Jeep doesn't lack for power while driving with the 4.10's and 37s. I don't think Georgia has mountains higher than the Sierra Nevada mountains right?? Since our Jeeps are mechanically identical, why is it I can go faster, up steeper grades, at less RPM's?

Everyone else who's replied has said "You need to re-gear", but I don't think they're really seeing what you're issue is. Should you re-gear with 37's? Yes, but with the 2.0 and 4.10's, you should not be struggling uphill with the pedal to the floor and only at 70 mph.

I think there is an issue with the transmission, computer, something. I have no clue what it could be, but I'd start with the transmission and associated control modules since that's what you had worked on.

Do you have a Tazer or comparable programmer in use to reprogram for your tire size? If not, then maybe get one to see if that helps. The auto trans shift points are based in part on tire size and gear ratio.

Your Jeep should be a blast to drive in it's current build configuration. There is something wrong, get it checked out and fixed AND then consider if you need to re-gear.

 

[intentsrig]

How’d you suck water into the transmission?

 

[InvertedLogic]

Did you correct your speedometer yet?

 

[InvertedLogic]

Your jeep doesn’t know you put larger tires on it. All it knows about how fast it is going is what rpm the wheel speed sensors are spinning at, and the ecu does some math to calculate speed and it assumes stock tire side.

As a test, pull up an app on your phone like Waze that shows your speed and compare it to your speedometer.

The fox is either to get a programmer like the TazerJL or AEV Snap pr have the dealer reprogram the ecu with the correct tire size. The ecu also needs this info to choose the right shift points for the trans.

 

[urr2slo]

I have the 3.6 and regeared to 5.13s, problem solved.

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