A few off road questions

[Fred63 Advanced Member Find all posts View Profile Close Fred63]

And second start.

Learnt that real quick. nearly buried myself in sand when i didn't use it in soft sand.

[JohnC80 Junior Member Find all posts View Profile Close JohnC80]

Regarding 2nd start. Can't you just tap the auto up to 2nd as you take off. You would move less than a ft before it hits 2nd.

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

Regarding 2nd start. Can't you just tap the auto up to 2nd as you take off. You would move less than a ft before it hits 2nd.

Why when there is a button there already?

[JohnC80 Junior Member Find all posts View Profile Close JohnC80]

Maybe you want 3rd gear so 2 quick taps will do the trick. But as explained I'm new to these prados.

[Fred63 Advanced Member Find all posts View Profile Close Fred63]

the Prado will always start in 1st unless you use 2nd start
in S mode it will only change up to the gear you have selected.
If you select 3S it will shift thru the gears but not shift any higher then 3RD
it does not automatically change to the selected gear.

[JohnC80 Junior Member Find all posts View Profile Close JohnC80]

So if you select 1st, let foot off brake and the car starts to move. If you hit the selector to 5th for example would it change to 5th gear immediately.

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

So if you select 1st, let foot off brake and the car starts to move. If you hit the selector to 5th for example would it change to 5th gear immediately.

No.

[JohnC80 Junior Member Find all posts View Profile Close JohnC80]

Thanks. Might have been part of my problem as 1st low in the soft stuff won't cut it.

[vk2ss55 Senior Member Find all posts View Profile Close vk2ss55]

Hi r4ndll
I can't understand how you can have an uneven front to rear power split when there's a mechanical connection from the transmission to the front and rear diffs . I could understand if there was some sort of hydraulic coupling in the transfer case but I'm pretty sure there isn't . Can you please explain where you got this info from ?
Cheers Ross

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

Google Torsen differentials.

https://m.youtube.com/watch?v=JEiSTzK-A2A

That is a rear differerential so 50:50 split. I will try and find an easy explanation of the torque splitting centre diff.

https://en.m.wikipedia.org/wiki/Torsen

Doesn't explain how though.

http://torsen.info/products/T-3.htm

The essential difference is where the output shafts are driven from by the planetary gears.

[r4ndll Avid PP Poster! Find all posts View Profile Close r4ndll]

Hi r4ndll
I can't understand how you can have an uneven front to rear power split when there's a mechanical connection from the transmission to the front and rear diffs . I could understand if there was some sort of hydraulic coupling in the transfer case but I'm pretty sure there isn't . Can you please explain where you got this info from ?
Cheers Ross

note - I got it wrong about 100% as the toyo site says max 30/70% split, but in everyday use (unlocked) its 40/60%.

The centre diff is not a normal diff, it's a mechanical LSD called a TORSEN (TORque SENsing) diff that allows power to be apportioned differently. Different designs of the gears allows a different bias to be applied front and rear. Toyota use the Torsen III in the Prado, to be explicit, which uses planetary gears to allow the diff to distribute torque unevenly between front and rear axles during normal operation without inducing wind-up.

Some light reading for you:

http://www.awdwiki.com/en/Torsen/
https://en.wikipedia.org/wiki/Torsen
https://youtu.be/JEiSTzK-A2A



The actual figures come from Toyota themselves:

http://www.toyota.co.nz/about-toyota...-road-terrain/

At the heart of Prado's full time 4WD system is a Torsen mechanical limited-slip centre differential.

The Torsen LSD system helps optimise traction.

The torque sensing system can automatically and instantly change the torque split ratio front and rear depending on driving conditions.

Under normal conditions the drive torque is split 40% front, 60% rear and is variable up to 30% front, 70% rear dependant on driving conditions.

For example, the system provides a 30:70 torque split when the vehicle is accelerating around a curve to suppress the chance of under steer and enhance cornering performance.

In more aggressive off road situations, the centre differential can be locked using an electronic system. Locking the centre differential splits drive torque 50:50 between the front and rear axles, making it easier to navigate rough terrain.

[batb0t Lurker Find all posts View Profile Close batb0t]

H4 is pretty good most times but I agree when the sand is so soft you are down to 16psi and below L4 is the only sensible choice. And second start.

Wow never thought of using 2nd start in L4 - cheers!
Can't wait to give it a go... having the trans move through L4 1st gear is painful (and slightly boggy)!

Great thread

[Stoo Junior Member Find all posts View Profile Close Stoo]

Just thinking about why low range may be better than high range in soft sand. It reminded me of the argument about towing and not to go above 4th gear because in 4th gear the torque converter 'locks' whereas in other gears it doesn't.
Does this explain why the transmission stays cooler when driving in low range through soft sand - because you're more likely to be in 4th gear rather than 2nd or 3rd?

[mjrandom Out of control poster! Find all posts View Profile Close mjrandom]

I'd say it is about torque input. If you need 800Nm at the wheels in high range you are inputting (say) 100Nm from the engine in high 2nd while in low range that is 50Nm. Ish.

[MidLifeCrisis Out of control poster! Find all posts View Profile Close MidLifeCrisis]

A few untruths here, allow me (self proclaimed expert to correct them):

1. The 150 Prado is in H4 permanently
2. The 150/120 Prado uses a Torsen LSD centre, it is neither open nor locked
3. The centre Torsen diff can be locked at the push of a button in either H4 or L4
4. The torque split is always 1:1 (often incorrectly referred to 50:50 - why not call it 200:200? see?)
5. There is about a 10% difference (seat of the pants) difference between unlocked centre and locked centre with TC still on\
6. There is a very slight difference between H4 TRC and L4 A-TRC (H4 retards throttle and brakes wheels, L4 only brakes wheels)
7. 99% of the time if your tyres are down to 18psi you can drive on and off the beach and along it in H4 with both TRC and VSC on and it won't bother you (I have extensively tested this and it so long as you are not half bogged leave it on, but there is no harm in turning it off)
8. I tested climbing a 600mm high vertical drop off in H4, L4, diff unlocked and locked and found the best combo with TWO wheels off the ground was ironically L4 diff UNLOCKED, don't know why.
9. The off road manual clearly states to leave the diff unlocked and only lock it when you are having trouble
10. THe prado will not spin one wheel if it comes of the ground, one rear wheel always has drive (centre diff lcoked or unlocked) the difference is about 10% drive loss in LSD mode.
10. You can tackel 90% of off-road terrain in H4 with TRC and VSC still on
11. L4 is useless on sand, the 410nm or 450nm is more than enough to move the Prado along with ease in H4, L4 will just burn fuel and heat the engine and oil up for zero benefit. (always makes me laugh watching someone revving the crap out their car in L4 and going no where, while someone else idles along slowy behind them in H4 1st or 2nd.

I agree with Simo except for point 9. Too much video of others with one rear wheel in the air failing to go where I have gone with front and rear lockers which suggests otherwise. Oh, and no idea re point 1.

One other quick point after reading all this, be kind to your rig, if you have lockers, use them, centre diff lock, use it when in HL, LL, or normal in a Grande. Look after the rig and it will take you just about anywhere.