Top speed in 4L

[Fly-by]

Hello,

I recently took delivery of a 2023 JTM with 6 speed manual. I bought it to cover ground quickly on FS and logging roads. In 4L it won't go over about 45 mph vs the stated limit of 50mph. It's not HP or RPM limited. Pulls well to about 4k then just stops. Not a hard, jerky cutout like a rev limiter, but definitely limited. I drove test another Sport S on 35s with 3.73s and it would do 52mph or so. Any theories on why this might be happening? Please no questions about why I want to go 50mph in 4L. Just want the vehicle to work as advertised.

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[AstroZombie]

interesting, i've never needed to go 45 mph in low range.

 

[AstroZombie]

not that i ever noticed the speedo

 

[kevman65]

Jeep did something in the transfer case to achieve that 50 MPH in 4Lo on the Mojave. Only model that has the change.

Don't know if it's a guaranteed 50 MPH or an in the neighborhood thing.

 

[Fly-by]

I know it sounds kind of trivial but it amounts to a 10% reduction in top speed in a range I regularly use. If it were 5 mph off the 2h top speed I wouldn't care at all.

Not sure it's Mojave specific as the Sport has the same 2.72:1 T-case and did a little over 50 mph. I think it's the Rubicon that has a unique lower limit of 20mph due to it's 4:1 T-case.

 

[KevinM60]

Here's a copy and paste from the Owner's Manual on the subject

___________________________________
2H
Two-Wheel Drive High Range — This range is for normal
street and highway driving on dry, hard surfaced roads.

4H
Four-Wheel Drive High Range — This range maximizes
torque to the front driveshaft, forcing the front and rear
wheels to rotate at the same speed. This range provides
additional traction for loose, slippery road surfaces only.
N (Neutral)
N (Neutral) — This range disengages both the front and
rear driveshafts from the powertrain. To be used for flat
towing behind another vehicle.

4L
Four-Wheel Drive Low Range — This range provides low
speed four-wheel drive. It maximizes torque to the front
driveshaft, forcing the front and rear wheels to rotate at
the same speed. This range provides additional traction
and maximum pulling power for loose, slippery road
surfaces only. Do not exceed 25 mph (40 km/h).
The transfer case is intended to be driven in the 2H
position for normal street and highway conditions, such as
hard-surfaced roads.
In the event that additional traction is required, the
transfer case 4H and 4L positions can be used to lock the
front and rear driveshafts together, forcing the front and
rear wheels to rotate at the same speed. The 4H and
4L positions are intended for loose, slippery road surfaces
only and not intended for normal driving. Driving in the
4H and 4L positions on hard-surfaced roads will cause
increased tire wear and damage to the driveline
components. For further information on shifting into 4H or
4L Ú page 150.
_________________________

HTH

 

[DylanM]

I feel sorry for the planetary gears in that transfer case.

 

[sharpsicle]

Why are we trying to go 50 mph in 4L? Shouldn’t we be using 4H for that?

 

[KevinM60]

Why are we trying to go 50 mph in 4L? Shouldn’t we be using 4H for that?

That's how I use it.
From what the Manual says there's no limit in 4H and 25mph max in 4L.
I use that 4L torque when crawling or climbing where I need the power but when I'm on open dirt or sand roads it's 4H and bat-out-of-hell speed when I can.
It's fun sliding around soft curves at 65mph while feeling in total control of the slide. My first time at Ocotillo I learned that 4x 360s leave 4 tire tracks instead of just the two rear tires.
Learn something new every day.

 

[Dartboy]

Jeep touted the 50mph top speed in 4L for the Mojave in a lot of places-

The numerically shorter ratio in the Mojave T-case allows a higher top-speed of up to 50 mph in low-range. The Gladiator Mojave can generate much higher wheelspeeds in low range than the Rubicon for running sand dunes and prerunning

https://www.motortrend.com/news/jeep-jt-gladiator-mojave-vs-gladiator-rubicon-whats-the-difference/

Maybe it's the 6MT limiting you? What gear are you in? Is the clutch slipping?

 

[Moe-Jave]

Why are we trying to go 50 mph in 4L? Shouldn’t we be using 4H for that?

Speeds “up to 50 MPH” makes sense in 4L for deep sand with the Mojave. Many prefer 4L for dune running, and that appears to be a design decision for the JTM.

This is also a good option to manage thermal thresholds between 4H and 4L as needed.

 

[FloridaMan655321]

Why are we trying to go 50 mph in 4L? Shouldn’t we be using 4H for that?

NO! 4L or GTFO!
Kidding, yeah, I wouldn't even use Low for anything close to 20mph. Kind of awesome someone got those gears screaming though

 

[KevinM60]

Jeep touted the 50mph top speed in 4L for the Mojave in a lot of places-

I like that.
Makes me wonder if my Owner's Manual is generic and not Mojave specific

 

[Fly-by]

Jeep touted the 50mph top speed in 4L for the Mojave in a lot of places-

https://www.motortrend.com/news/jeep-jt-gladiator-mojave-vs-gladiator-rubicon-whats-the-difference/

Maybe it's the 6MT limiting you? What gear are you in? Is the clutch slipping?

5th or 6th around 4500rpm and the clutch is definitely holding. If Jeep advertises and rates it to 50 mph, it should perform that way out of the box. I put down a deposit on 5.38 gears for install around Thanksgiving so this may resolve itself if 3rd becomes usable in 4H. Still not acceptable.

 

[sharpsicle]

Everything I see says something to the effect of “around 50 mph”. Nothing guaranteeing you will actually hit 50 mph.

I wouldn’t be too worked up about it.

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