Should I regear?

[cutter1138]

Hello all,

So, I have been having issues with the way my gearbox is acting for some time, as well as what i would consider dismal fuel economy. Now before anyone says anything, I understand it's a big heavy brick being pushed through the air and that it's not prius (thank God.) But I have been routinely getting 14.5 on the highway.

So my setup is as follows:
JT rubicon with 4.10 gears
2 inch mopar factory lift
35x10.50R17 kenda Klever tires (an experiment that has gone pretty well so far)
ARB Bondi delux full width bumper with 9500lb winch
Best top soft cap for the bed
xtrusion overland XTR-1 bed rack with a small roam case on top

The gearbox holds 7th almost all the time, and will periodically try to go to 8th and then drop down to 7th almost immediately. I have been to the dealer and they were less than helpful. The gearbox has no error codes and the y just put it back into learn mode. I have calibrated the tires on two separate occasions despite getting basically the exact same measurements.

My question is would it be worth regearing? and if so, what gear set would you all use? I have been thinking about 4.88. I want to be able to tow a trailer out west some in the future this requires pulling up some significant mountains. I have gone into the weeds a little bit and have been thinking that a shorter gear would help given the weight and drag produced by the jeep, this would raise the engine RPM some but would off load the engine with the mechanical advantage from a shorter final drive ratio. I would use 8th gear more and might actually see an improvement in range (Mostly what I am interested in for going on long trips).

Am I thinking about this correctly or am I missing something?

Thanks

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[bleda2002]

Hello all,

So, I have been having issues with the way my gearbox is acting for some time, as well as what i would consider dismal fuel economy. Now before anyone says anything, I understand it's a big heavy brick being pushed through the air and that it's not prius (thank God.) But I have been routinely getting 14.5 on the highway.

So my setup is as follows:
JT rubicon with 4.10 gears
2 inch mopar factory lift
35x10.50R17 kenda Klever tires (an experiment that has gone pretty well so far)
ARB Bondi delux full width bumper with 9500lb winch
Best top soft cap for the bed
xtrusion overland XTR-1 bed rack with a small roam case on top

The gearbox holds 7th almost all the time, and will periodically try to go to 8th and then drop down to 7th almost immediately. I have been to the dealer and they were less than helpful. The gearbox has no error codes and the y just put it back into learn mode. I have calibrated the tires on two separate occasions despite getting basically the exact same measurements.

My question is would it be worth regearing? and if so, what gear set would you all use? I have been thinking about 4.88. I want to be able to tow a trailer out west some in the future this requires pulling up some significant mountains. I have gone into the weeds a little bit and have been thinking that a shorter gear would help given the weight and drag produced by the jeep, this would raise the engine RPM some but would off load the engine with the mechanical advantage from a shorter final drive ratio. I would use 8th gear more and might actually see an improvement in range (Mostly what I am interested in for going on long trips).

Am I thinking about this correctly or am I missing something?

Thanks

Are you going to 37's any time in the future? If so go 5.13's as they will handle 37's with towing and/or mountains much easier. If you plan on sticking with 35's 4.88 would be fine. I can safely say that in no way shape or form do I regret going 5.13's as it completely transformed the jeep to make it very pleasant even on the big tires.

For reference, Jeep puts 4.56 gears on the XR for its small/light metric 35's, and offers 4.88 for even stock size tires (32.5's or so) on the jl, so anything less than 4.88 is probably not worth the money, and 5.13's isnt much of a stretch.

 

[mdyucca]

By regearing you will be happier with the daily drivability. By regearing you will not see a significant increase, if any, in your fuel economy. It would be interesting to know your Gladiators empty weight as built with a full tank. City driving I average 14.5 mpg. Thankfully fuel prices have dropped a bit.

 

[QuintusMaximus]

You're thinking about towing a trailer? Yes, you should definitely regear. You're already borderline with your current tires and probably should have already geared, but adding towing makes it pretty clear, IMO. Might want to go even higher than your planned 4.88.

Regarding the fuel economy on the highway, what speed are you going? You're going to notice a massive difference between say 60mph and 80mph. If you're getting 14.5 mpg but you're going 80mph, that isn't surprising at all. I bet you'd get close to 20 if you went 65. I don't have to commute (work from home), so I'm never driving when I'm in a hurry, and usually don't have long drives to make, so I have switched to driving in the slow lane going the speed limit, helps a ton with fuel economy.

 

[cutter1138]

Have you installed a Tazer or equivalent to change the tire size in the computer? This helps.

Yes, I have done that. then questioned myself as to whether I had done it correctly so I went back and got a new set of measurements, and they were within a 1/6th of the previous ones.

 

[cafecito]

Have you installed a Tazer or equivalent to change the tire size in the computer? This helps.

This. If your ECU still thinks you're on the stock "33" (31.5") tires, it's going to shift at much higher RMPs than necessary.

14.5 is super low. I just went up to 37s and I am still between 16 and 17 most of the time (no bed rack, but Mopar steel all the way around the truck, so I'm not exactly a flyweight).

 

[cutter1138]

You're thinking about towing a trailer? Yes, you should definitely regear. You're already borderline with your current tires and probably should have already geared, but adding towing makes it pretty clear, IMO. Might want to go even higher than your planned 4.88.

Regarding the fuel economy on the highway, what speed are you going? You're going to notice a massive difference between say 60mph and 80mph. If you're getting 14.5 mpg but you're going 80mph, that isn't surprising at all. I bet you'd get close to 20 if you went 65. I don't have to commute (work from home), so I'm never driving when I'm in a hurry, and usually don't have long drives to make, so I have switched to driving in the slow lane going the speed limit, helps a ton with fuel economy.

I generally run about 70-75mph on the highway. I mean it's a Jeep after all. On state highways I will typically run 55-65. it will do a little bit better at 60.

 

[dcmdon]

The truck will drive better. But to think you are going to get any kind of real improvement in fuel economy with lower gears is kind of fantasy. The transmission is already compensating by running in 7th most of the time.

All of your mods will work against getting decent fuel economy.

I have a Mojave (same gearing) with a cap and 35s. Stock plastic bumper. At 70 mph on the highway, I'm in the 17s in the summer and about 15 in the winter.

Pushing highway cruising speed up to 75 mph would surely knock another 1 or 2 mpg off.

Drive slower.

Do the math. Unless you are running late for something it's not worth going faster than 70.

 

[Uparms]

my 35x12.5 -17slove the 8 speed. I get 8ths sometimes, but off the line and highway driving it is great with factory 4.10s. 17.5 average MPG right now winter gas combined hwy/city. 19-20 when I am on the big highway.

 

[CrazyCooter]

Yes

 

[Lunentucker]

Heavier tires.
Heavier bumper.
Winch.
And you added more brick to your brick.

I've been toying with manually keeping mine in 8th when I'm not in a hurry and cruising along. Typically, the first sign of the slightest incline and it wants to go to 7.
Holding 8 seems to make a substantial difference in the instant mpg and the overall.

Most don't regear for 35s but when you factor in all the other things you've added in weight and brickness, it might not be a bad idea.

You can divide the cost of regearing by the anticipated savings on mpg to see how many years it will take to break even.

 

[jeepstertim]

I have a JTR on 35" with a 1.5 level, canopy, tent, bumper etc. and granted my BFG KOs are small 35s, but they're also light. Tank to tank over the last 6 months I have averaged 20.22mpg and while I sit on the motorways at 65-70, the jeep also sees a good amount of off-road and dunes.

I see 8th 90% of the time but gradients and a decent headwind will have the box dropping to 7th but at 65/70 mph, that keeps the RPM low and the economy good.

None of this really helps you but unless you're caning it, you should be getting better and in my experience, a regear shouldn't really be needed.

 

[Blade1668]

My heavy ass JT gets around that when towing and all the S### it's got loaded in it. With hardshell RTT (that knocked off a few MPG's) from the over 20 MPG's I averaged before if I keep speed under 70 it's better. No lift with 4:10 gears and 33/10.5x17 E rate aggressive AT tires. It will start hunting gears and drop down to 4th on grades towing to almost single digit MPG if big hills.

So if you're asking If you need to re-gear you probably know you want to or need to already. Now the question is what ratio do you want? IMHO I wouldn't regear from 4:10 to 4:56 or 4:88s if it was my $$$ and I was doing a regear it would be the 5:13 or so. 4:56 or 4:88 wouldn't be worth the time or money to make it worth while to me. My XJ had 3:54/3:55 gears stock with 29/30in tires stock I re-geared to 4:56 and ran heavy ass 33/12.5x15 MT and was getting close to 20 MPG afterwards with 35s the speedometer was on. Not the same thing but something to put it in perspective. My LJ is currently on the 33s with 3:73 gears and is a dog on road with them, with 31 MT tires it wasn't too bad....

 

[jensjer]

Hello all,

So, I have been having issues with the way my gearbox is acting for some time, as well as what i would consider dismal fuel economy. Now before anyone says anything, I understand it's a big heavy brick being pushed through the air and that it's not prius (thank God.) But I have been routinely getting 14.5 on the highway.

So my setup is as follows:
JT rubicon with 4.10 gears
2 inch mopar factory lift
35x10.50R17 kenda Klever tires (an experiment that has gone pretty well so far)
ARB Bondi delux full width bumper with 9500lb winch
Best top soft cap for the bed
xtrusion overland XTR-1 bed rack with a small roam case on top

The gearbox holds 7th almost all the time, and will periodically try to go to 8th and then drop down to 7th almost immediately. I have been to the dealer and they were less than helpful. The gearbox has no error codes and the y just put it back into learn mode. I have calibrated the tires on two separate occasions despite getting basically the exact same measurements.

My question is would it be worth regearing? and if so, what gear set would you all use? I have been thinking about 4.88. I want to be able to tow a trailer out west some in the future this requires pulling up some significant mountains. I have gone into the weeds a little bit and have been thinking that a shorter gear would help given the weight and drag produced by the jeep, this would raise the engine RPM some but would off load the engine with the mechanical advantage from a shorter final drive ratio. I would use 8th gear more and might actually see an improvement in range (Mostly what I am interested in for going on long trips).

Am I thinking about this correctly or am I missing something?

Thanks

Why not use the "manual mode" of the auto trans to keep it in 8th or whatever you want on those long drives?

 

[teamblkdog]

I'm heavy with an Alu-cab canopy camper on the back and average 14.5 at 65 on the highway with 33s. MPG goes up to 16-17 when I'm consistently driving in town. No regrets going to 4.88.

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