Low Range

Submitted: Friday, Jan 09, 2004 at 13:43
ThreadID: 9613 Views:1466 Replies:10 FollowUps:9
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Just curious on what I read in an earlier post. How much time, offroad, do you spend in Low Range?
I personally use it constantly and very rarely use High Range unless it's a graded dirt track or I'm on sand. The rest of the time I use low, the 60 series can do about 50kph in 5th low range and I figure if anything I'm gunna want to go lower rather than higher in gearing? Am I a weirdo or do others use lowrange for the majority of their time offroad?
Cheers,
Justin
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Reply By: troy - Friday, Jan 09, 2004 at 14:06

Friday, Jan 09, 2004 at 14:06
i have limited knowledge on this subject but here goes.
I believe you can spend all your time in low range if the track conditions are appropiate. When i went to Spicer Gap and Sundown National Park one lond weekend I lived in low range bar the high way section between the 2 parks.
I would be very cautious about using 5th gear in low range. Check your 4wds booklet to check if they recomend it. I may be wrong but a diff is very expensive to replace
troy
AnswerID: 42353

Follow Up By: pathfinder - Friday, Jan 09, 2004 at 16:44

Friday, Jan 09, 2004 at 16:44
would say it's more likely to be fifth gear in the gearbox that will need replacing as it's an inherently weak gear and shouldn't be subject to the huge torque produced in low range. I would recommend only using low when absolutely necessary - high range results in less stress on the drivetrain and produces better fuel economy...unless you're labouring excessively of course...
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Follow Up By: GaryInOz (Vic) - Friday, Jan 09, 2004 at 18:35

Friday, Jan 09, 2004 at 18:35
The low range actually roughly halves the torque load on the 5th gear, all the torque multiplication occurs at the transfer gearset not in the transmission. The reason it is not suggested that you use 5th is that 4th is usually a "straight through" locked mainshaft 1:1 ratio and is inherently stronger than any other gear, therefore thought to be more reliable. Notwithstanding that, the 5th gearset is usually the weakest of all of them and is better avoided in anything but flat level ground in 2WD.

Low range can give you an edge in controllability in some instances and better engine braking as well.
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FollowupID: 304836

Follow Up By: Bonz (Vic) - Saturday, Jan 10, 2004 at 08:38

Saturday, Jan 10, 2004 at 08:38
Gary,

Doesnt the torque multiplication occur thru the application of the gearing, i.e 300Nm at the flywheel via a 1:10 gearing gives 3000Nm at the back of the gear box, if 5th gear is at the back of the gear box then it'd get a lot of that extra torque. I ony use low range to 4th gear also due to the "straightthruness" of the gearset

You choose your gears for whatever you are doing, personally I choose high or low back and forth depending on what the track is looking like, mind you once i went down this hill in 4H should have DEFINITELY been 4L silly bugger!, but 4H still turns all the wheels and is easier on the whole vehicleLaterally Literal
Seriously Cerebral
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FollowupID: 304872

Follow Up By: GaryInOz (Vic) - Saturday, Jan 10, 2004 at 18:15

Saturday, Jan 10, 2004 at 18:15
"Doesnt the torque multiplication occur thru the application of the gearing, i.e 300Nm at the flywheel via a 1:10 gearing gives 3000Nm at the back of the gear box, if 5th gear is at the back of the gear box then it'd get a lot of that extra torque. I ony use low range to 4th gear also due to the "straightthruness" of the gearset".

Yes it does, but through each succesive gearset. For example consider a gearbox with 1st gear of 3:1, 4th gear 1:1, and a transfer case high of 1:1 and low of 2.5: 1, and consider points A input to gearbox, B output of gearbox/input of tcase , and C output of tcase.

With 200 Nm at point A:
In 1st high there would be 600 Nm at point B and point C,
In 4th high there would be 200 Nm at point B and point C.

In 1st low there would be 600 Nm at point B and 1500 Nm at point C,
In 4th Low there would be 200 Nm at point B and 500 Nm at point C.

"... but 4H still turns all the wheels and is easier on the whole vehicle...".

Not really.

From looking at the above example it is clear that in 1st high both the gearbox and tcase are stressed to 600 Nm, wheras in the 4th low example, the gearbox only has 200 Nm going through it and the tcase has 500Nm (roughly equal in reality due to friction losses). The tcase is designed for continuous running in low ratio whears the gearbox is designed with a definite duty cycle to get to 4th gear (ie not "live" in 1st, 2nd or, 3rd).

I think there is also a little bit of confusion about "...the back of the gearbox...". This refers to the output shaft and not to the physical location (most 5th gearset are located physically at the rear but in mechanical reality are driven by the same shaft that drives all the other gears). The 5th gearset will recieve the same 200 Nm (in my example) input toque as any of the other gearset would, but it would produce LESS torque output ie. 160 Nm with a 20% overdrive at our point B.

Not criticism, just education......... :-))
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FollowupID: 304912

Follow Up By: GaryInOz (Vic) - Sunday, Jan 11, 2004 at 07:57

Sunday, Jan 11, 2004 at 07:57
"From looking at the above example it is clear that in 1st high both the gearbox and tcase are stressed to 600 Nm, wheras in the 4th low example, the gearbox only has 200 Nm going through it and the tcase has 500Nm (roughly equal in reality due to friction losses)...."

Clarification: "...roughly equal in reality..." was referring to 500 Nm vs 600 Nm.
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FollowupID: 304953

Reply By: Moose - Friday, Jan 09, 2004 at 14:51

Friday, Jan 09, 2004 at 14:51
I use it extensively offroad too but I slip back into high range on any sections where a bit of speed is reached. Don't like going quickly in low. It's easy enough to go from one to the other on the move so I prefer not to stress things out (which I suspect speeding in low range probably does - but I may be wrong).
AnswerID: 42361

Follow Up By: Leroy - Friday, Jan 09, 2004 at 14:58

Friday, Jan 09, 2004 at 14:58
I'm the same Moose.

Leroy
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Reply By: MikeyS - Friday, Jan 09, 2004 at 15:28

Friday, Jan 09, 2004 at 15:28
I tend to stick to (s)low range a lot of the time on slower tracks because the gear ratios are effectively closer together so I get a better choice of gears. Sometimes I just want that extra "in between" gear which I can get in low range.
AnswerID: 42366

Reply By: paul - Friday, Jan 09, 2004 at 16:26

Friday, Jan 09, 2004 at 16:26
i only use low range when i am bogged or to get through a sandy section if i think i might get bogged.

High i only use on soft sandy stretches where i know my AWD wheels are spinning but am doing 60km's and don't wanna be slowed down by being in low range.

i also have a petrol so being in low range means you can see the fuel gauge dropping so i stay out of it if i can.
AnswerID: 42371

Follow Up By: Rob H - Friday, Jan 09, 2004 at 17:02

Friday, Jan 09, 2004 at 17:02
Hi Paul

Forgive my ignorance - I've only ever used low range for extra grunt pulling a boat up a slippery boat ramp / crossing a creek etc.

What advantages have you found in using low range for boggy / slippy / sandy situations? Is it not simply a questions of switching the diff lock on?

Rgds

Rob
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FollowupID: 304820

Reply By: jeff-wa - Friday, Jan 09, 2004 at 17:04

Friday, Jan 09, 2004 at 17:04
My manual TD I used to always be in low if I was around sand or rutty/rocks, high on the tracks. Now I have an auto TD and very rarly touch the leaver!
Low did use a little more fuel, mainly because I would get slack and let the engine work a little harder, also I imagine long periods of Low would heat up the gearbox and transfer case (might be wrong?!) But I agree I probally wouldn't be using overdrive in 5th unless I was just cruising on a gravel track, and then would probally just switch to high anyway.
AnswerID: 42374

Reply By: paul - Friday, Jan 09, 2004 at 17:13

Friday, Jan 09, 2004 at 17:13
To Rob H

Hi Rob

I could be ignorant as well but with an RV6 petrol 90 series prado i find that when bogged in sand 1st low range gets me out of anything 1st go with the tyre pressures reduced. I have tried variouis high range gears but the wheels spin to much digging me in. So its just a matter of gearing. On the other hand going into a boggy section if i want to plow through it i'll hit it in second low at about 3600rpm and it just churns through anything, but if it is just sand and i think momentum will get me through then i save the petrol by plugging it in about 2nd high range and hit it with a bit of speed (speed that i can't easily get it to in low).
AnswerID: 42375

Reply By: paul - Friday, Jan 09, 2004 at 17:15

Friday, Jan 09, 2004 at 17:15
To Rob H again

the other thing - the diff lock - on RV6 manual 90 series prados the diff lock is locked automatically once you shift out of normal gearing into either high or low, there is no manual switch.
AnswerID: 42376

Follow Up By: Bonz (Vic) - Saturday, Jan 10, 2004 at 09:02

Saturday, Jan 10, 2004 at 09:02
the diff lock you refer to is only the centre diff, not a cross axle diffLaterally Literal
Seriously Cerebral
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FollowupID: 304874

Reply By: colin - Friday, Jan 09, 2004 at 19:06

Friday, Jan 09, 2004 at 19:06
Hi Justin, depends on what your vehicleis and how it is set up, i have a GQ patrol 4.2 diesal with a super charger fitted, i very rarely use low range as my set up has so much torgue that i can stay in a higher gear and use less revs and just idle along at 1000- 1500 revs which means less fuel. Some vehicles are not able to tow or labour in 5th gear but i have found with the GQ 4.2 diesal the gear box is in destructable, i have done 270000 ks towing large boats and camper trailers long distance useing 5th and have had no problems at all, i also drive around town in 5th at about 1000revs. Servicing with good quality oils regulary is also a must. Col
AnswerID: 42382

Follow Up By: David N. - Friday, Jan 09, 2004 at 22:55

Friday, Jan 09, 2004 at 22:55
G'day Col,
Hows the FnFNQ treating you.

I use low range off road if and when it suits- the GQ Gbox is built like a brick outhouse and used sensibly will last forever. Have always used whatever is the most sensible gear for the situation which sometimes favours low ratio and sometimes high. Have also always used 5th gear as much as any other with no dramas in 13 years- probably a third of my kays have been towing and much of that in 5th gear!!
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FollowupID: 304857

Reply By: Mad Dog Morgan (Vic) - Friday, Jan 09, 2004 at 21:08

Friday, Jan 09, 2004 at 21:08
Used low range today. A few steep down hills. Don't like riding the brakes.I may be mad but I'm not crazy
BEAM ME UP SCOTTY
â
Hooroo
Ray
AnswerID: 42406

Reply By: Member - Toonfish - Friday, Jan 09, 2004 at 23:20

Friday, Jan 09, 2004 at 23:20
give me low range first in my diesel and as happy as a pig in poop whether uphill or downhill i love crawling the bigguns .
without lower tyre pressure, low gears in diesels tend to dig in soft stuff.1999 NISSAN NAVARA DUALCAB
DIESEL 3.2 & SPRINGY CARLTON TOY
2 awestruck kids (dads driving!)
AnswerID: 42417

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