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Gwagensteve wrote:After 2 high performance front wheel drive road cars I can tell you exactly why I drive a full time 4WD (STi WRX) It's as fast and sticky on a wet road than a front wheel drive in the dry.
Steve.
Fast and Sticky.
2 things full time 4WD's are not.
AWD's, well, that's a whole other kettle of fish
AWD and 4WD. Isn't the official difference that AWD does not have an option for low gearing via the transfer case, whilst 4WD do.
Full time 4WD have a centre diff, Part time don't???
My mate has had GQ and GU Nissan Patrols and has just purchased a L/Cruiser V8 T/T diesel. He reckons he will never purchase a part time 4WD again due to the stability and traction he gets out of the Toyota.
When he had the Nissans, he would whack it down to 4WD if the bitumen road was wet but realises that he would have been loading up his transfer case in doing so and wonders why he never broke one.
he never broke anything because ita s patrol
Oh well, he did throw a rod out the side of his block when on full boost.
I am the Nightrider! I am the chosen one. The mighty hand of vengeance, sent down to strike the unroadworthy!
bad_religion_au wrote:
why??? a part time 4wd is a 2wd when driven on road when it comes to economy figures.
i'm not disputing complexity, traction gains or anything else, JUST the claim that AWD's/full time 4wd don't use more fuel on the road.
A part time 4wd in 2wd is heavier and still has more turning parts than a 2wd version of the same vehicle.
Final drive ratios are often different as well.
Hence not a good comparison.
My fulltime 4wd rangerover gets better economy than any part time diesel hilux.
me3@neuralfibre.com wrote:
How many part time 4wd cars don't even have free wheeling hubs on many variants?
Land Rover never fitted FWHs from the factory - probably as the engineers realised they were useless, and it was better for lubrication to keep everything turning (How many PT toyotas and nissans have to get diffs replaced because 1/2 the crownwheel is rusty and pitted).
FWHs were offered by dealers though, and seemed to really gain popularity in the 70's (when fuel prices were high). Same time some cars were fitted with vacuum gauges.
ROGQ wrote:But isnt it true that if you own a full time 4wd that you should lock the centre diff in this situation.
No, it's not true.
ROGQ wrote:I have heard that the actual center diffs themselves aren't the strongest things and on loose traction surfaces such as dirt roads they spin like crazy causing premature wear.
That's wrong. The only way the centre diff can "spin like crazy" is if the front and rear driveshafts are at massively different speeds. If all four wheels are travelling at roughly the same speed, how will that happen?
ROGQ wrote:If this is true then they dont really offer an advantage over part time on the dirt.
It's not true, there's no problem, they really can offer an advantage over part time on the dirt.
When a vehicle travels around a bend, all four tyres travel a slightly different distance. A part time 4wd (or locked centre diff) needs a tyre to slip to "correct" for this difference. In a full time 4wd (with unlocked centre diff) the differentials allow for the difference, and no tyres need to slip. That sounds good to me.
FWIW, on soft sand on a beach, I find it easier to drive with the centre diff unlocked - the car seems happier to follow existing wheel ruts and doesn't throw from side to side as much.
I dont think the front and rear shafts would have to be at massivly different speeds. On a dirt road there will be wheel spin, proably so minute you wont even notice it. But this is enough to make the centre diff work hard causing early wear. This was said by Peter @ Aawen4x4 on the 4wd monthly forum
Just be a little wary of running a constant 4WD on dirt roads WITHOUT the centre diff lock engaged! If the road is loose enough to allow wheel spin at either end, then your centre diff is going to be spinning like a banshee!! And those centre diffs are much smaller than the diff at either end of the car! You let them spin due to differences in wheel speed at each end too much, and they wear out fairly quickly!! That's why there are guys around the place making a MINT out of converting constant 4WD's to Part Time 4WD's! So where there is a likelihood of poorer traction allowing different wheel speeds at each end, or wheel spin anywhere, you should be engaging the centre diff lock, or you WILL pay the penalty (unless you manage to unload the car onto some other poor sucker first!)
ROGQ wrote:I dont think the front and rear shafts would have to be at massivly different speeds. On a dirt road there will be wheel spin, proably so minute you wont even notice it. But this is enough to make the centre diff work hard causing early wear.
You really don't understand how diffs work.
ROGQ wrote:This was said by Peter @ Aawen4x4 on the 4wd monthly forum
I've read Peter's posts on diffs before. Now I know where you developed your understanding.
ROGQ wrote:Just be a little wary of running a constant 4WD on dirt roads WITHOUT the centre diff lock engaged! If the road is loose enough to allow wheel spin at either end, then your centre diff is going to be spinning like a banshee!!
No, it won't.
ROGQ wrote:And those centre diffs are much smaller than the diff at either end of the car! You let them spin due to differences in wheel speed at each end too much, and they wear out fairly quickly!!
No, they don't.
ROGQ wrote:That's why there are guys around the place making a MINT out of converting constant 4WD's to Part Time 4WD's!
Like Peter?
ROGQ wrote:So where there is a likelihood of poorer traction allowing different wheel speeds at each end, or wheel spin anywhere, you should be engaging the centre diff lock, or you WILL pay the penalty (unless you manage to unload the car onto some other poor sucker first!)
You really shouldn't go around preaching on subjects you don't understand. I'll continue to use 4wd on dirt roads, and have all four tyres gripping at all times. You continue to use 4wd on dirt roads and have tyres randomly slipping.
ROGQ wrote:
I dont think the front and rear shafts would have to be at massivly different speeds. On a dirt road there will be wheel spin, proably so minute you wont even notice it. But this is enough to make the centre diff work hard causing early wear. This was said by Peter @ Aawen4x4 on the 4wd monthly forum
If you are scared of your vehicle parts "wearing", then leave it safely locked up in the garage.
I have a fulltime 4wd transfer box which has done around 500,000km (speedo says 330,000, it has been wound back an estimated extra 200,000km). It is not worn out.
ROGQ wrote:
Just be a little wary of running a constant 4WD on dirt roads WITHOUT the centre diff lock engaged! If the road is loose enough to allow wheel spin at either end, then your centre diff is going to be spinning like a banshee!!
That's what diffs are made to do. I can light up individual wheels on dry tarmac and haven't yet blown one up.
I have no idea why people want to convert a fulltime 4wd vehicle to part-time, but those guys aren't going to get any money from me. The reasons you've listed are fiction.
ROGQ wrote:I dont think the front and rear shafts would have to be at massivly different speeds. On a dirt road there will be wheel spin, proably so minute you wont even notice it. But this is enough to make the centre diff work hard causing early wear.
You really don't understand how diffs work.
ROGQ wrote:This was said by Peter @ Aawen4x4 on the 4wd monthly forum
I've read Peter's posts on diffs before. Now I know where you developed your understanding.
ROGQ wrote:Just be a little wary of running a constant 4WD on dirt roads WITHOUT the centre diff lock engaged! If the road is loose enough to allow wheel spin at either end, then your centre diff is going to be spinning like a banshee!!
No, it won't.
ROGQ wrote:And those centre diffs are much smaller than the diff at either end of the car! You let them spin due to differences in wheel speed at each end too much, and they wear out fairly quickly!!
No, they don't.
ROGQ wrote:That's why there are guys around the place making a MINT out of converting constant 4WD's to Part Time 4WD's!
Like Peter?
ROGQ wrote:So where there is a likelihood of poorer traction allowing different wheel speeds at each end, or wheel spin anywhere, you should be engaging the centre diff lock, or you WILL pay the penalty (unless you manage to unload the car onto some other poor sucker first!)
You really shouldn't go around preaching on subjects you don't understand. I'll continue to use 4wd on dirt roads, and have all four tyres gripping at all times. You continue to use 4wd on dirt roads and have tyres randomly slipping.
as i said guys, was said on another forum. Thanks for clearing it up.
Kiwi I Think the point was not parts wearing,of course all parts wear. but the point was reducing the wear. And i think the point he was saying is that the centre diffs are only small diffs, not that strong.
Scott no i dont know how diffs really work, and im not preaching mate. Just trying to bring up a point that may help people out, and if i was wrong, it is now cleared up so more poeple like me who didnt know now understand. Thats what these forums are for, im entitled to post just as you are. No need to be so uptight and smart.
ROGQ wrote:Scott no i dont know how diffs really work, and im not preaching mate. Just trying to bring up a point that may help people out, and if i was wrong, it is now cleared up so more poeple like me who didnt know now understand. Thats what these forums are for, im entitled to post just as you are. No need to be so uptight and smart.
My apologies for mis-interpreting your post. At times I get frustrated by seeing statements which are just plain wrong being repeated on multiple forums. The internet is still the world's best source of incorrect information.
When a differential is locked, both output shafts turn at the same speed. When it is unlocked, and there is only a minor difference in wheel speeds, such as when rounding a bend, the difference in shaft speeds is the same as the difference in wheel speeds - minor, and, as you pointed out, barely noticeable. The amount of wear caused by such a difference in speed is so small that I struggle to work out how it could even be measured.
If one shaft is spinning and the other shaft is stationary, then I agree that this is not an ideal situation, but it will still not cause significant wear - any such wear would need to be measured over years, not hours or days. But such a high difference in shaft speeds will not happen during "normal" driving on dirt roads.
lay80n wrote:Totally random though, the Dana solid axles under your jeep have uni joints, not CV's. So just like in your driveshafts they have an acceleration and deceleration phase. Maybe a possibility. Or it could be the ackerman angle is not perfect, making the tyres scrub, or it could be the toe-in/toe out variation on the wheel alignment. There may be a million and one things. Many cars will start to chirp/scrub the edges of tyres at full lock.
Layto....
I spoke to Hammond 4WD (Jeep Specialist) about it and they say it's normal because it has a tighter turning circle and different design. It's normal isn't a good enough explanation for me though.
Shane
be from under steering, as in your simply pushing the front wheels forwards while on full lock.
lower the power output on the motor that would fix that problem, lol
ROGQ wrote:And i think the point he was saying is that the centre diffs are only small diffs, not that strong.
As with everything else, this is also wrong. Centre diffs ARE geometically smaller than diffs in axles, but for the amount of torque they see, they are quite strong.
Torque is multiplies by the gearing. The axles see torque loads which are 3-5x what the centre diff sees.
The rockcrawling guys who use rover full time t-cases use the handbrake to lock the rear output solid, forcing the front output to spin (to do front digs). They rarely break anything (in the t-case).
im not to sure about the nissan, toyota and other brands of 4wd systems, but the landrover fulltime system in early rangerovers, early discoveries and all coil sprung landrovers is very good and easy.
you can have 4 high or 4 low on tarmac no worries. very very handy with loads, trailers, boat ramps etc
lock the center diff by moving lever to the left. NO ELECTRICS full mechanical system!
now i have driven all landrovers. i tell you with any load or a trailer fulltime is great = better handling, better grip, better braking
as far as free wheeling hubs on part time 4wd systems, stop kidding your selves they dont make enough of a difference to fuel consuption.
as far as saving those moving parts.... well they were designed to move and should be to be kept in good working order.
i really dont see how going back to 2wd in a defender can be any good, yes it will reduce backlash, but if its that bad maybe it needs adjusting or parts replaced! i tow a big ass trailer everyday in my 110 and the back lash isnt that bad.....
One thing that seems to be missed in all these discussions is the legality of converting a factory full time 4wd to a part time. If the vehicle left the factory with full time 4wd it is illegal to alter it in any way without an engineers certificate and compliance plate. If you have an accident without one it gives the insurance companies one more reason to deny your claim and may well render your vehicle un-roadworthy in the eyes of the law. The regulations about modifications are screwed down pretty tight and worth a read if you plan to modify your vehicle.
Alan.
Was talking to a fella who converted his LC80 to part time not long after he bought it many moons ago. Why? He didn't like how it drove. He wanted it to feel more like his Patrol did. He also disliked the amount of diff backlash provided by having 3 girly little diffs working on rotating his wheels. He said that after the conversion his fuel economy improved by ~2L/100km, tyres were chewing out less and it was a much nicer vehicle to drive.
Still wishes he still had his patrol though.
Not really useful but meh. I prefer AWD where available. RWD is alright but in a patrol it sucks. When 2.5t of mass breaks traction in the wet its usually a matter of hold on tight and hope for the best.
As what happened to me this morning. Must have hit a bit of diesel on the road or something becaue the bastard thing broke loose at no more than 30km/hr and i was the passenger in a magnificently slow 180 degree slide where my steering and throttle inputs did not affect the direction of travel in the slightest. Was hillarious at the time.
Yom wrote:Was talking to a fella who converted his LC80 to part time not long after he bought it many moons ago. Why? He didn't like how it drove. He wanted it to feel more like his Patrol did. He also disliked the amount of diff backlash provided by having 3 girly little diffs working on rotating his wheels. He said that after the conversion his fuel economy improved by ~2L/100km, tyres were chewing out less and it was a much nicer vehicle to drive.
I've heard the exact opposite experiences from an 80 series converted to part time.
Became a dog to drive, especially in the wet and cornering. So much so that when it was sold, the next one was kept full-time.
I find 2L/100km improvement highly suspicious. Unless he had no oil in his front diff.
99% of people who prefer part time 4WD must be people who own that kind of vehicle and can't accept that an alternative design might be better.
Anyone who converts a full time 4WD to part time may have some reasons, but guaranteed he is also one of those people who does a lot of other weird shiat that leaves people scratching their heads.
A lockable centre diff is a great thing to have in a 4WD, definitely better than not having one.
Gwagensteve wrote:After 2 high performance front wheel drive road cars I can tell you exactly why I drive a full time 4WD (STi WRX) It's as fast and sticky on a wet road than a front wheel drive in the dry.
Steve.
Fast and Sticky.
2 things full time 4WD's are not.
AWD's, well, that's a whole other kettle of fish
My STI is more of a "4WD" than a 44" tyred car with open diffs - it runs three tight LSD's stock.
I (seriously) don't know what the difference is between a 4WD and an AWD. I know that most people think an AWD doesn't have a low range, but that's not relevant to this discussion.
I'm not actually crazy about the handling of constant 4WD cars (or 4WD's) but they do improve traction and drivability, especially in the wet and in cars with a large range of loaded/unloaded mass.
Steve.
The STi u drive does it comes with helical, suretrac or proper competition clutch pack lsds in the front and rear?
Are u running a viscous coupling center diff or the DCCD?
Always wondered how does the funky electronic diff works.
So cool u can lock it 50:50 or bias as much to the rear wheels.
I heard if u have the Motec ECU with the software unlocked u can mess around with the center diffs settings to apportion the right amount of torque.
To be on the safe side nothing beats full time 4wd.
But if u want to drift all day, a miser when it comes to fuel consumption part time.
Anyway we shouldn't be driving 4x4s to begin with if i want to be stingy and safe the environment.
