Help understanding Drivetrain

[spooler]

Hi all!

I have a 2007 ML Triton Auto with factory locker and I recently got it seriously bogged for the first time
I am not an experienced 4WDer but the guy with me was and I followed his advice. We went down a track at a farm we were spotlighting on. I wasn't going to go but he wanted a look and the last time I was there it was dry so I left it in 4H. Went around a bend and there was mud and water everywhere! Cool I thought as I ploughed in and keept the momentum up and it was squidgy but all good.... no fear of bogging there. The Dick Cepek F-CII's in 265/75/16 were doing well considering there was 38psi in them and I never intended tackling really muddy shite! Anyway, got to a section where the track looked like an olympic swimming pool ahead to I hard righted it into what looked like a grassy area to do a 3 point turn.... this is where the grass was only a thin veneer over clay As soon as I slipped I should have gone to 4L but didn't as my mate said 'she'll be right!' We let the tyres down to 20PSI (had no compressor and 30kays to the servo) and stuffed sticks under the rear and front tyres. Still no luck and 4L was engaged. There was some crunching of gears when Reverse was selected but he said that was cause the drivetrain was loaded due to us being in a hole. Anyway, down to the question....
The rear locker was on so I understand that both rear wheels would have been spinning at the same time but my front drivers was stationary. Others have said that the front passenger one would have been spinning and the LSD prevented the front drivers from spinning but my boss here at work has been 4WD in jeeps (he is an American.... and made me show him where this mud was!!) for decades and recons that once in 4L the LSD should be negated but others have said to do that you need to fit a front locker as well. I thought you either got a front or a rear and not both? Is this the way the Triton drivetrain works or is there a potential problem? Maybe the grinding upon engaging 4L meant that it didn't engage and was in some 'phantom' gear and hence was only in 2wd?? Thanks for any explanations!!

Andrew

[daryn]

Quick comment Spooler,

4wd means that front and rear wheels should be spinning, with the rear diff lock both rear should be, with no front diff lock either both or at least one should be spinning.

You do not have a LSD in the front, 4L does not negate any rear LSD if fitted, 4L only alters the gear ratios to lower gearing of course.

You can have both a front and rear locker of you choose to fit them.

Just because you slipped does not necessarily mean you should have gone to 4L, it just means that in 4H you would have had to negotiate the obstacle still with the correct amount of revs but at a higher speed.

Are you thinking that you have a front LSD ? If you have a rear diff lock you do not have any LSD's installed in your truck at all, I think the term is open diff (someone correct me) for the front.

Not knowing how far you have travelled, but it seems you had travelled well over 100m in 4H prior to the wet stuff, so your front autolocking hubs should have been engaged by then for sure. Maybe the transfer lever was not engaged correctly, hence as well the problem going into reverse.

LSD's are for rear only.

[spooler]

Daryn,

Thanks for the info. Definately only a rear locker not a front and it seems from your comments as well as other elsewhere that the front right not spinning indicates that the front left was and that this is normal. I am not going to get a front locker fitted since I doubt it would have helped in this instance and also I am not a mad keen mud runner!!! Hence the AT tyres even if they are pretty aggressive.

The car had been in 4H for about an hour prior so was definately locked in.

Thanks for the info re LSD diffs as well.

Andrew

[NowForThe5th]

With the Easy Select you have no centre differential - just a transfer case which splits front/rear 50:50. So, if you were in 4WD High or Low your front wheels would be getting drive if the front "hubs" were engaged (these are actually located inboard at the diff but the effect is the same). Was your dash light flashing or steady? Quite often the front does not engage straight away and needs the front wheels at the straight ahead position. If the light was flashing then you were still in 2WD hence no drive at the front. Hard to say without being there but there are only two possibilities as I see it: that you had not engaged 4WD (or maybe disengaged but not re-engaged) or that there is/was a problem with the front axle drive engagement.

The front diff is "open", i.e. not LSD or lockable so drive will go to the wheel with the least traction.

The new, Super Select system is quite different and drive can vary front to rear to quite some extent but never 100% one way or the other.

[spooler]

Yeah I have no doubt that the 4WD hubs were engaged. I had been driving everywhere that night in 4H since I didn't want to rip up the farmers pasture by spinning the back wheels and it was quiet wet there. I never disengaged the 4WD so going from 4H to 4L shouldn't be a prob. When 4L wouldn't engage at first I did go back to 2H but didn't engage drive so the hubs would have remained locked. The little light stayed solid orange as did the rear locker indicator so I am sure the passenger side front wheel would have been spinning like a mad man!

Thanks for all the advice guys. Will just have to alter my driving habbits and learn a bit more about offroad driving.

Andrew

[chick_magnet_0001]

was in a similar situation i found 4high with the centre diff lockedand rear locked(ie 4h in a glx/ 4hlc in glxr,vr,gls best for getting out of mud because you have the wheel rpm to clear mud going forward and in reverse, it just low range seemed to slow and the clutch slip of 4h was very little due to the torque of the 3.2d(probly could have pushed my ute out in 4L 1st and jumped back in to driveaway, would have made it interesting

[Homer]

Sometimes it's worth riding the foot brake just a little to get both fronts driving - works better when crossed up than in mud though I think - maybe not effective in that situation.

[spooler]

Yeah I think that I was just plain out of luck the minute I dug myself into that slop.... will be getting some of those roll up trax before tackling anything like that again!!! And using them before I dig a hole a foot deep