Highest gear in low range JLR

[J0E]

I've been told a Rubicon won't shift into overdrive (7&8) in low range. What's the fastest a JL Rubicon will go in low range? A crawler I talked to said it's a PITA to stop and shift into high range after you crawl over an obstacle and you've got half a mile or more of 2 WD type dirt road and want to go 35 MPH.

In the good old days of manual hubs and xfer cases, the year was 1977. I was poor and my friend was poor. His parents divorced and his mom bought him a new dodge 4x4 truck with a V8 and automatic. The rich kid in the school had a new CJ with a stick. Rich kid was constantly making fun of the Dodge, so I challenged him to a light to light drag race. The entire school came out expecting to CJ to blow away the truck, but the opposite happened. I had my friend put it in low range and the fast shifting automatic combined with low gears blew away the CJ.

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[jludave]

What's the fastest a JL Rubicon will go in low range?

Please get a copy of and read the Owners Manual.

https://carmanuals2.com/d/115996#page155

4WD Low
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).

 

[J0E]

4WD Low
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).

Is that the non-ruby 2.73 or the Ruby 4:1 xfer case?

It multiplies the torque to front and rear, not just front. It can't provide any more traction, it's a pure torque play. My 1964 manual said the same thing and I routinely drove it 45 MPH.

My corvette manual said don't exceed 100, lol.

 

[jludave]

Is that the non-ruby 2.73 or the Ruby 4:1 xfer case?

It multiplies the torque to front and rear, not just front. It can't provide any more traction, it's a pure torque play. My 1964 manual said the same thing and I routinely drove it 45 MPH.

My corvette manual said don't exceed 100, lol.

That’s from the 21 owner manual. It applies to all JL models. I just copied what’s there. It also didn’t say it multiples the torque. It says it “maximizes” the torque to the front driveshaft so that it forces the front and rear wheels to rotate at the same speed.

It’s ultimately your vehicle. If you wish to exceed 25mph in 4 low, it’s your choice.

 

[SilverSurfer]

I would sometimes use 4L in sand depending on the obstacle and the auto would shift to 7th and 8th easily when I need a bit of momentum to get up a sandy climb but I hardly exceed about 25Km/hr.

I've had 3 JKs and shifting between 4L and 4H in the JL is a lot easier compared to the JKs.

 

[jludave]

I would sometimes use 4L in sand depending on the obstacle and the auto would shift to 7th and 8th easily when I need a bit of momentum to get up a sandy climb but I hardly exceed about 25Km/hr.

If you hardly exceed 25Kmh (15.5Mph) in 4 low, you wouldn’t be in 7th or 8th gear.

 

[SilverSurfer]

If you hardly exceed 25Kmh (15.5Mph) in 4 low, you wouldn’t be in 7th or 8th gear.

I can use my GoPro, record it and show you.

 

[J0E]

I can use my GoPro, record it and show you.

No need. Using the diff gear claculator.xlsx that one of our members provides, with a stock JLR 4:1 transfer case
5,000 RPM in 6th gear is 29 MPH
43 MPH in 8th gear, but it might not go into 2nd over-drive.

 

[J0E]

@wibornz wrote here next time I'll search from google

I think I have been close to 50 mph in 4lo on the sand dunes. It is better to get the speed up for the bigger climbs and manually downshift as you climb.

 

[SilverSurfer]

No need. Using the diff gear claculator.xlsx that one of our members provides, with a stock JLR 4:1 transfer case
5,000 RPM in 6th gear is 29 MPH
43 MPH in 8th gear, but it might not go into 2nd over-drive.

That calc is max RPM speed per gear. In real terms the box will be in 6th and I am doing about 10Km/hr.

 

[J0E]

I added https://bt39.azurewebsites.net/GearWheelSpeed to my site, quick prototype.

@wibornz must have been redlining it.

@SilverSurfer
I'll add a KPM checkbox for you, hadn't thought of that.

I'll add non Ruby xfer case, stick, and other rigs. In the mean time you can edit any parameter.

 

[word302]

It’s not that hard to shift between low and hi

 

[jessedacri]

My JLR regularly sees 7th and 8th in 4L when at trail speeds in between obstacles. The 8AT trans is awesome in 4L because you have such a wide range of speeds available without shifting in and out of low constantly. You're also certainly good to hit 25mph in 4L as the manual states.

 

[J0E]

Just added Gears, wheel, speed to my web site. JLR can do 37 in 8th, a non-ruby 55.

 

[gato]

Just added Gears, wheel, speed to my web site. JLR can do 37 in 8th, a non-ruby 55.

That is with stock tires, I assume. With larger tires you'd be going somewhat faster.

I'll relate that I did higher speeds for a few minutes in between obstacles in my JKUR, and I will never do it again. Even in top (5th) gear in the auto the engine was screaming and there was a distinct smell of things heating up.

I will now pop out of 4L anytime I need to move above 10 or 15 MPH or so for any duration that is more than a few seconds.

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