Programmer or ReGear

dstonerii

Jeep Newb
I have a 2014 JKU Sport automatic trans. I have a 3.5" MC GC, 35x12.5 and factory 3.73 final drive. When I got the lift everyone tells me I need to regear. I purchased a traildash2 to reset the speedo and to give me gauges ( I like to know what my temps and such are). I pull a popup camper (1500LB). So the tow mode and crawl mode are bonus features. I get 18-20 mpg wheelin or not. I now have 80K on it. it is my DD and I offload often.

What is your opinion on gearing or programming? I really don't understand why everyone is saying I need to regear.
 

TheGrendel

Jeep Owner
a programmer and gears are not the same thing. the programmer helps with shift points (if automatic) and making sure the speedo is correct. gears put your engine back in the correct power band.

now, if you are ok with how your jeep drives on and off the road with your current set up then you don't need to change. me personally i don't know how you live with it. i had 13 JKR auto with 4.10 gears and when i went to 35s i always felt the gearing was wrong. now, i have a JKUR 6mt with 4.10s. haven't decided if i'm going 35s or 37s yet. if i go 35s, i'll probably stick with 4.10s for awhile. but if i go 37s, ill regear quickly.

i question very much the claim of 18-20 mpg.
 

macgyvr

Jeep Newb
If it's working for you, then don't regear.

When you add lift and tires it takes your motor out of the factory set power band for the speeds in which you are driving.

When you regear you bring the motor back close to the factory power band so your performance is better. I always go a little more gear than I need to help make up for the extra weight of the wheels and tires and lost aerodynamics. My LJ with 33s is geared to 4.56 gears when the numbers show it could be 4.10s. Yeah its a little more rpm at cruising speed, but it's better performance getting to cruising speed.

Performance programming can help, but it will never replace a regear. I think folks think that the programming can replace a regear because you can do it for cheaper and do it your self. It never really replaces a regear. I think that both a programming and a regear is the best answer. A regear will also put your speedo back to reading close to correct as well.

If I was towing regularly, I would do both. If I could only afford one, I always regear.

Is your 18-20 mpg hand figured or is it off a lie-o-meter?

mac 'all geared up' gyvr
 

Pthorpe84

Moderator
Staff member
Macgyvers advice is sound. I would tell you that I am on 4:10’s and 37’s. It is very doable, much like the 35’s. I would suggest you look at swapping to 4:56 gears only if you are going to tow.

You won’t get 18 mpg. Not on average. 16 would be a good number.

The traildash is needed anytime you go to larger tires for speed-o. Gears are a must if you want the power back like stock. I can’t wait to get 5:13’s. I miss being able to pull trailers up a hill.


Sent from my iPhone using Tapatalk
 

Roan

Jeep Newb
If it works and you like the way it drives, leave it. Especially with 18-20 mpg.

I run a 2016 JKUR on 35s with 4:10s and the same lift and I do just fine. I did the programmer to correct my speedo.

+1 for a regear if towing, but again if it’s working for you...

How do you get 18-20 mpg??? I’m lucky to get 16 on the freeway?!?!?!
 

Brian

Jeep Fanatic
I say Re-Gear 100% and here is why.

First, to really get that fuel mileage one must advance the timing to be right on the edge of spark knock. Does that mean your traildash2 programmed anything when it adjusted the speedo? Probably not, and you are probably not getting 18....

But a programmer would work to get more power out of the motor, advancing the timing, adjusting fuel rations and overall making more heat. Now you start towing with that package with larger tires and you really start making heat. Lets say that the radiator can keep up with the heat created so you really do not notice. But there will be significant increases in stress on the motor because of the programmer and towing.

Re-gearing would allow for less torque to be needed to turn your tires and to tow. Your engine would not have as much load and you would then have less stress on the motor and drivetrain. If you want your Jeep to last longer, re-gear.
 

ratchettt

Jeep Owner
Agree with most comments. I had 4.1 gears with stock tires and got used to the great torque. After moving to 35's the performance downgrade was too much to stand. Biggest decision was 4.56 or 4.88. All this was before adding weight associated with bumpers, winch etc. You will be glad you re-geared in my opinion.
 
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