Low range 4X4 wont engage.

[Tailwheel]

Hi Guys, Normally I would engage low range every few months when on sand or grass, or at least off hard surfaces. But lately it has not been done resulting in needing LOW 4X4 and it is not engaging. Hi 4x4 is fine , just the LOW range light flickers but does not engage. I removed the wiring connectors and cleaned then to no avail. Usually when engaging LOW range it 'clunks in' quite loudly, but it's not making a sound.
Any clues welcomed ?

[mydmax]

Hello TW
Do you select high 4 before trying LOW or do you simply push the 4Low button? I ask this because the transfer case has to first determine if the system is stationary or spinning, ie, like shifting to H4 on the fly. That means the TC system has to accelerate to front drive shaft for the SOTF system to engage. Unless the SOTF system has engaged for 4WD then the LOW won't work until it has settled the SOFT system on the front axle. I always select H4 first and when OK then select 4L because the SOTF system is already engaged the front axle shafts. Mine won't go from H2 to L4 without first selecting and confirming H4 on the way through. Sort of two stages of selecting L4.
Therefore, if the SOTF system isn't providing H4 then L4 won't select, ever. The problem may be the front axle SOTF system isn't working, check that H4 is attained before looking for L4 problems.
If H4 is OK and you know drive is going to front wheels, then look at the rear of transfer case s=where the wiring goes into the servo drive unit. If not used for a while the contacts in there may be cruddy and not allowing the shift to 4L. Check wires there too because any fracture may not signal to the controller any feedback info to the shift controller. I think shift controller is under the drivers seat so look there, seat out probably, to make sure the empty stubbies haven't dislodged the connecter of the controller and all wiring and connectors are good.

Hope you find it!

[Tailwheel]

Thanks for the reply MD,
I have always selected H4 before attempting to engage L4, and followed the book. Had it on the hoist to check wiring etc and all appears OK, cleaned the contacts which were a tad cruddy but still no luck. Re empty stubbies under the seat,,,, How did you know? Will pull the seat out first thing tomorrow and check, [and get rid of the empties too]
Will let you know tomorrow,

Cheers,

[mydmax]

TW
Not sure if I mentioned it properly, but if the wiring for the front SOTF system is faulty it may stop the controller from allowing L4 to engage. I will have to think a bit harder about it. It is all sequenced and each section, ie, 4WD and Low 4 probably has to have the SOTF system definitely driving as 4wd before the LOW aspect becomes active and the normal clunk is heard. The clunk is the servo motor on back of transfer case moving the selector ring from high to low as it engages the dog clutch for the epicyclic reduction. If it is not aligned or slightly moved to allow alignment of the dog, then the servo motor will time out and the flashing will stop and go off. The dog clutch is why LOW cannot be engaged while rotating. Slight movement sometimes required to allow engagement, ie, suddenly into drive and immediately out for an auto or clutch out to friction and in again for a manual.

I use free wheel hubs so I can maneouvre trailers, etc, without windup of driveline and often a bit of jiggle is needed to get it into 4Low.

[Tailwheel]

Thanks MD,

Got all of that thank you.
Pulled the seat and no wiring found bar the seat belt loom, and same on pax seat too.
I found some older posts WRT the SOTF functions and 4x4 engagement/disengagement problems, so it's back on the hoist for another look see.

PS: Do you truly think that Nulon works?

[mydmax]

TW
The SOTF change box has about 110ml of oil in it, or should have. Best to check that. Mine does have some Nulon in that oil too, 90 w from memory. If it isn't achieving lock up then Low won't select. If H4 is achieved then that may be operating ok. Then the problem is more likely to be in the TC area, servo or wiring. Unless there is physical damage inside the TC then the servo motor , it's contacts and wiring may be the problem. I haven't opened the rear of the TC servo area, ie, under a round cap, but the system usually, in most vehicles has a rotary plate which send contact info back to the controller by changing finger position on a series of circular tracks. If they are dirty, burned a bit or not touching then motor drive and sensed position of the change system won't be fed to the controller and it will time out.
Have you checked the oil level in the TC?
Yes I do think Nulon G70 does help, only a small percentage of the total volume is required. Not to be used in an LSD or auto box though. I have Nulon G70 in the SOTF system, front diff and transfer case. I always use it in starter motor bearings and Nulon grease in reduction gears mixed with Mobil 1 if just a fluid is required. I use Nulon grease in front wheel bearings and uni joints/ grease gun. Mobil 1 being synthetic doesn't dry out much as plain oil does over time and so allows mechanisms to be lubed for longer, especially aircon blower fan bearings/bushes love it. No more fan resistors burnt out. Some may not agree but it is what I do.

[Tailwheel]

Another excellent post MD, more food for thought. Back up on the hoist when I get the chance, thanks again.