Front/rear diff lock reluctant to disengage

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

On our recent snowy trip there was a day we were in and out of diff lock nearly every time we drove the car. The locking mechanism was really reluctant to disengage after the gear lever was changed. The light on the dashboard stayed on and I could feel the car was still in locked mode. It took sometimes 10 little changes from forward to reverse to 'bump' the diff lock out, which is a bit annoying in a queue of snow traffic.

We use the car 99% on bitumen and the diff lock is only used very occasionally. Whenever we are on any sort of soft surface I always try to engage the diff lock for a few metres to lubricate everything in the transfer case.

Is there any ideas on things I might do before a trip to help with this problem?

Does turning too tightly on a hard surface with the diff lock engaged cause it to jam in place as the places I had most trouble I had just left a tight parking spot with the lock engaged?

And 1 more question: when parked at the snow resorts and snow is expected should it be left parked in locked mode? I worry about being stuck if unable to get the transfer case gears to change when so cold.

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

My old 90 had the same issue just putting it in low.

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

Hey Robbo,

I don't believe there's any need to engage H-Lock just to "lubricate" the gears as the lock/unlocked gears are all located in the same part of the case anyway. In actual fact there's more planetary gears in use when it's unlocked. Do it if you like, or not - whether you practice it or not, there's no harm.

Nothing to be done before trips - except of course the usual maintenance items which includes replacement of the transfer oil per schedule (can't recall, is it every 50k?).

The most important point is that you're correct about avoiding sharp turning whilst H-Lock is engaged. It definitely does cause significant strain on the drive line & transfer and makes it harder to disengage the lock. Whilst it is possible to engage/disengage lock on hard surfaces, it's better to do so loose surfaces instead.

Remember:
- Engage/disengage H-lock during straights, preferably soft surfaces.
- When H-locked avoid the combination of hard turns and hard surfaces.

If you find yourself caught on a hard surface with H-Lock engaged, lets say when parked, your first attempt to disengage the lock should be by shifting into Neutral. I find neutral helps significantly in most cases. If not, try driving out of the spot in a straight motion, then return to the spot (back and forth) - the further you drive without turning the better. Again, popping into neutral once and a while can often solve it. Any minor turns you make during this process should be equalised with a proportional amount of turning in the opposite direction.

If those first two methods don't work and you must exit the parking with a sharp turn, do so, but you'll need to release the "transmission wind up" as soon as possible by turning in the opposite direction. Ie, if you exit a parking in forward direction whilst turning sharp right (wind up), you should continue straight until your first opportunity to turn left (release). Avoid turning right a second time as it will increase the wind up. You'll feel the tension build up through the steering wheel during your first sharp turn, and when turning the opposite direction you should feel the steering get lighter again.

It's okay to continue a few hundred metres down a tarmac road whilst trying to disengage the lock, as long as you're staying reasonably straight and trying to release the wind up tension via minor corrective steering. Again, pop into neutral occasionally.

Finally, I would avoid this entire scenario by leaving the centre UNlocked unless absolutely on loose surfaces. There's no need to lock up for parking on a hard surface even if there is snow, as the open 4WD system in this transfer seems to work well enough on snow. Even if lock is required the next morning, it'll engage very easily in slippery conditions.

[Anth120playdo Banned Find all posts View Profile Close Anth120playdo]

Yes Toyota does recommend engaging it once a month for lubrication. But I wouldn't stress.

Try making sure your driving str8 whenever you want to engage, or disengage.

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

Yes Toyota does recommend engaging it once a month for lubrication. But I wouldn't stress.

Try making sure your driving str8 whenever you want to engage, or disengage.

Who or what document from Toyota recommended this? Does it apply on the 90? They have different transfers then 120/150's.

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

Yes Toyota does recommend engaging it once a month for lubrication. But I wouldn't stress.

Try making sure your driving str8 whenever you want to engage, or disengage.

Who or what document from Toyota recommended this? Does it apply on the 90? They have different transfers then 120/150's.

Yes #### where is this written and which models does it apply to? Bit confused. I know the 90 used to be troublesome getting in and out of 4wd at times but the 120 and 150 (both electrically actuated) have been no issues so far though I guess Hutch will beg to differ.

Not the Prado but since putting the FEL on the tractor I need to run that in 4wd all the time so at the end of the day I lift the front wheels off the ground and drop the transfer case back into 2wd to let the drivetrain relax a bit. Without lifting the front wheels there are times when even strong language won't shift the lever from 4wd to 2wd.

[Anth120playdo Banned Find all posts View Profile Close Anth120playdo]

Who or what document from Toyota recommended this? Does it apply on the 90? They have different transfers then 120/150's.

Not sure if its the back of the sun visor or the owners manuals I have read it in.
As you might know, the transfer cases are very similar.

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

are your tyres all the same size ???

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

Not sure if its the back of the sun visor or the owners manuals I have read it in.
As you might know, the transfer cases are very similar.

My feeling is that it's just something people like to do, after being used to the same practice on part time 4wd's with disconnecting hubs. However, you said "Toyota does recommend it for lubrication" - which has my interest. If that's true, I'd love to know why.

I thought the 120/150's have a slip-sensing torque system in the transfer? The 90 is completely open with a double pinion planetary gear set.

[glen_ep Addicted PP Member Find all posts View Profile Close glen_ep]

Yes Toyota does recommend engaging it once a month for lubrication. But I wouldn't stress.

Not sure if its the back of the sun visor or the owners manuals I have read it in.

I believe this is incorrect.

I've just checked my vehicle manual and the 4wd instructions attached to the sun visor, no such thing is mentioned.

I just wanted to be clear about this because stating "Toyota recommends..." can be quite misleading.

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

Are we talking manual or auto????
What oil is being used in the transfer case??? because if your have the wrong oil it doesn't like it very much so that could cause the issues your having.

With my vehicle, it drops in and out very easerly but it is an auto and last week while playing up on duck creek road I actually never had to lock the centre diff nor use the lockers on the front or rear while others (in Jeeps..... poor buggers..lol) had to.
It may be driving style, it may be a mechanical issue, I don't think anyone here can really say. All I can say is lock it in and out a few times each day at home in the driveway without moving the vehicle and see what it does.

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

Thanks for all the ideas. Sometimes in the resort car parks it can be impossible to find anywhere to drive in a straight line. The issues were a snow covered parking spot, a narrow road and no possible way to drive straight out of the parking spot, and wheels spinning in unlocked mode. Making the opposite turn to unlock the wind up would have taken us into the river!

Car is an auto, transfer case has correct grade of semi-synthetic Penrite gear oil.

My idea of lubricating the gears comes from the assumption the gears sit in a bath of oil and that oil is distributed around all 360 degrees of the gears only when they spin. By not spinning the Low Range gear it potentially sits at the some rotation and the top part is never lubricated. This is why I always like to engage low range whenever a soft surface is available, as it's pretty much a town car otherwise.

I'm pretty sure the transfer case oil is 40K, changed in the big 80K service and again each 40K in the medium service. The 40K has all the diffs and transfer case, the 80K has those again as well as the transmission oil. Car is around 190K so it's been 30K since the transfer case was done at 160.

I probably just would it up getting out of the parking spot.

I see your point that it's easy to get it into lock mode, so should park it unlocked. However when driving without any 4WD snow experience at all it's very hard to know when to engage the lock. It's too late when you are parked in the bushes after sliding off the road.

All the rangers tell you is to engage 4WD. Sorry mate, I'm already in 4WD!!!

I would have loved to take it for a spin across some real snow in the driveways of some of the lodges but was worried about getting stranded. Just how much snow can a Prado handle in Low range. I guess it depends on the tyres?

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

Car is an auto, transfer case has correct grade of semi-synthetic Penrite gear oil.

When you say correct grade, is that for hot climate or cold climate, if you use an oil that's ideal for hot climate is freezes in cold climates, you need to use a thinner oil to stop the thickening of the oil from the cold temps.
Same goes for using an oil designed for cold climates in hot climates, the oil is then too thin and doesn't lube all the bits that need lubrication.