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Apparently there are two school of thoughts.. one encourage driving in 4 L with 4/3 gear while the official version is to avoid. 

 

I would like to Offroader driving FJs to share their opinion on this.

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The owner manual will clearly mention that it should be avoided for speeds above 30-40 kmh. For speeds below that, you have indeed the choice of driving in 4L but then again why would you risk it ? and what would be the benefit of potentially damaging the transfer case ?

Driving in sand requires you to keep your engine revs in the powerband. If this can be achieved in 4H then this is by far the better option.

 

PS i am not an FJ owner (anymore) ;) 

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"Go as far as you can see; once you get there, you'll be able to see further."

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@Ashok chaturvedi also take into account the group and their link to certain garage(s) as a backdrop for their recommendations to run full ride in 4L.  

Also testing their recommendation comes at your own risk (vs theirs) - if you do play around with it to form your own decision, be sure to share your findings.  I accidently kept in 4L after a recovery and did a few climbs before noticing - I didn't 'feel' the benefits/difference however it was hardly a scientific test. 

Edited by Niki
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Not FJ, but I remember one of my convoy buddy @Ali Shahduring our last week drive in Liwa, mentioned that he struggled to climb on 4H but considerably better when he switched to 4L in his Pajero.

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Hello Ashok Bhai @Ashok chaturvedi thanks for asking this question . I am not an Fj owner . But this is the way how understand it  , please correct me all if I am wrong , and here I am talking about 4WD off course . HI gear it means that you can drive to higher speed because the gearbox will sheft you automatically up or you will manually if manual shift the stick from 1 to 2 from 2 to 3 .. etc and you gain more speed ( creat momentum ) with lesser Torque ( strain on the previous gear as you shift up ) . However aborting the sheft by keeping the stick on 2 for example or the gear shifter in D2 or even D1 your torque ( pull ) will increase to maintain the speed ( momentum ) but at the expense of your gear ⚙️ life span .

now at lower gear climb it looks like as if someone is winching you up hill with tremendous traction and if the engine power is given more input ( that’s why modern vehicles will cut it off no matter what you do as a protective mechanism ) your transfer case will die sooner or later .

for me the adequate speed builds momentum which is the one we rely on to take us from one dune to the next smooth and nice 

Edited by M.Seidam
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I drive my FJ on 4H, i had to engage the 4L only for self recovery and while declining a steep ramp for engine break. But 4H is doing just fine all the time at least for me, sometimes i keep a low gear on 4H when i need to climb up tall steep ramp but i keep it always on the High didn't need to go to 4L for high climb yet.

On the other hand someone kept driving on 4L because he didn't want to get stuck at the end the transmission overheated and broke in the middle of the desert but just to note it was a fast drive.

 

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*Not an FJC owner

The only time I actively use 4L for long-ish periods is when I’m doing climbs up extremely steep inclines in Wadis on rocks where my speed is never rising above 20 kmph. Through a consistent pressure on the pedal and carefully watching my RPMs, I find the 4L works a lot better than 4H when doing the steep grades.

Beyond this, in the desert, I rarely ever use 4L unless I’m doing self recovery. Switching to a lower gear and improving my line of ascent is a much better process for me.

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Hi @Ashok chaturvedi. I guess I know where your question is coming from. With bigboys drive, definitely 4L to keep up with the pace, especially for long high dunes that require power+speed.

With carnity drives, you are ok on high gear, which is definitely safer for the gearbox and the engine.

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Hi @Ashok chaturvedi, this is not an FJ-specific thingy, I have a marshal friend who drives his Jeep in 4L 3rd gear consistently and some Nissan buddies also drive in 4L 3rd gear. I will get into the general stuff first, and at the end dive specific to A750F transmission which is used by FJ Cruiser to answer your question mathematically 😁

1. Generally for older 4-speed & 5-speed automatic, people drive in 4H 2nd gear and downshift to 4H 1st gear when climbing or need more torque. In contrast for modern 6-speed & 7-speed automatic, some I've noticed drive in 4L 3rd or 4th gear. They're pretty similar, and I'll prove it mathematically at the end of this post...

2. My Nissan buddies drive in 4L 3rd gear because driving in 4L allows them to turn off VDC (Vehicle Dynamics Control - computer will try to brake to fix understeer & oversteer), TCS (Traction Control System - brakes spinning wheel + cut-off fuel to engine and/or close throttle valve to reduce torque) and ABLS (Active Brake Limited Slip - Nissan's version of Toyota A-TRAC), as can be seen from this manual section:

842089487_Drivemodes.jpg.76b9924299e2f2e55698a0bbdf9d594f.jpg

 

3. If you're already in 4L, during stucks you don't need to shift from 4H > Neutral > 4L > 1st gear 'cos you're already in 4L, which sounds like an excuse a lazy driver would make 😂

 

FJ Cruiser A750F transmission: 4H or 4L?

These are the Gear Ratios for FJ Cruiser / any car with Toyota A750F transmission: 

FJCruiserTransRatio.png.a518545dbbe800d86e3a4c8a9dda64a6.png

Now I'll probably do a deeper dive with diagram what these different gear ratios mean, but for now I will use a cheat calculator to produce the numbers:

Problem Question: I want to drive 50 km/h (31 mph) in sand, what do I use? *The 50km/h is intentional as some manuals recommend this speed when driving in 4L, and also on average we usually drive below this speed for Newbie to FewbiePlus

Putting the A750 Gear Ratio numbers above, you can easily reach 50km/h in 4H 1st Gear after around 4000 rpm, which is what you'll probably do when climbing a steep dune... then shift to 2nd gear to keep RPM below 3000 for noise & fuel-efficiency.

  • 3.727 : Differential Ratio / Final Axle Gear Ratio
  • 31.6" Tire Diameter,  FJ stock is 265/70R17
  • 31 mph : Desired Speed (50km/h) 
  • 3.520 : 1st Gear Ratio

FJ_4H_1st.png.da1bf671f9c7831be18ad631c6891287.png

4L and Gear Reduction

Transfer Case in 4H is 1:1 (mentioned in A750F spec as High 1.000 above), but when you switch to 4L, it becomes 2.566:1 , this is why 4L in 1st Gear is slower and useful for crawling (but still with torque). But for the sake of fun, how much engine RPM do we need to make 31 MPH in 4LO 1st Gear ?

  • Transmission Ratio now becomes = 2.566 (4LO) x 3.520 (1st Gear) = 9.032

FJ_4L_1st.png.f8c27473a9e5db692309147b0122cfc0.png

Your Tachometer is usually maximum 7000 rpm, so this 4LO 1st gear will not do, let's skip to 4LO 3rd gear:

  • Transmission Ratio now becomes = 2.566 (4LO) x 1.400 (3rd Gear) = 3.592

FJ_4L_3rd.png.f50abf2477b877b76e4750fc6f6a4455.png

And there you have it, using 4LO in 3rd Gear, you will reach 50 km/h (31 mph) after about 4000 rpm engine speed... very similar to 4H in 1st Gear...

To recap:  If you trust the factory's book recommendation and will not go above 50 km/h in sand, then 4LO sounds safe as it disables all those pesky electronics (VDC, TCS, ABLS, ABS) without pulling any fuse. Otherwise if you're driving long-range dunes and flats and will go beyond 50 km/h in sand, you may want to use 4HI + kill-switch to ensure ABS, TCS, VSC are off.

 

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