2001 Prado - Centre Diff Lock Problem

Submitted: Saturday, Apr 16, 2011 at 21:27
ThreadID: 85670 Views:7532 Replies:3 FollowUps:1
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Hi all,
I am hoping that someone here can shed some light on a problem I am having with my 2001 Prado(5 speed manual). Approximately 1 year ago, I cooked the oil in the centre diff whilst towing my boat. I had left the caravan park and about 10km down the road, I could smell this awful stench, which turned out to be the oil cooking in my centre diff. Stupid me left the stick in HL and hadn’t realized. I have no idea why I didn’t see that big orange light on the dash that tells you the centre diff lock is engaged. I took the car to my mechanic the next day and he changed the oil in the centre diff, he told me at the time that he did not detect any metal in the oil. A few months ago, I started to have trouble with my centre diff lock. When I shift between LL/ HL and H, the diff lock light on the dashboard would not extinguish. I would have to have to reverse the car down the road for a bit in order for the light to extinguish. I select low range when pulling my boat up the ramp, which is approx 60 meters total distance.

In recent weeks, things have now deteriorated to the stage where the only way I can get the light to extinguish is to jack up the front wheel and let it unwind. As soon as I jack up the front wheel, the light immediately extinguishes. Today I took the car down to a huge gravel car park and selected HL, as soon as I selected HL, I could here a meshing type noise coming from the front end. I immediately stopped and changed back to normal mode (H). No matter what I did, the diff lock light on the dash would not extinguish. I crawled home(which is 1km from the car park) and jacked up the front end and the wheel unwound and the light went out.
Do you think my centre diff lock is cactus ???

Regards
Jason
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Reply By: StormyKnight - Saturday, Apr 16, 2011 at 22:14

Saturday, Apr 16, 2011 at 22:14
Its pretty normal for the light to stay on or off when you have selected to unlock or lock the centre diff. The reason is the lever is just an electrical switch with gives power to a solenoid. The solenoid engages & disengages the actual locking of the centre diff. The centre diff will not lock in if the gears are not lined up. This often means having to drive a bit forward whilst turning the steering wheel so that the front diff rotates at a different rate to the rear diff. Similarly, if the car is locked in it will not release whilst there is pressure on the centre diff, so for it to unlock the pressure has to be released, again by turning the steering wheel to release the pressure.

If you have overheated the unit it may mean it doesn't operate as well as it did originally, perhaps the heat has affected the mechanism, but becuase you say you lift the wheel is enough to fix it, I can't see that being greatly different to moving the steering wheel.

BTW, you do have the same sized tyres with near equal wear on all 4 corners don't you? If not that will be your problem for sure. It will be impossible to turn enough to release the pressure without some tight turns.

The Prado is a constant 4WD, have you tried pulling the boat up the ramp without locking in the centre diff? If you are on concrete & a flat surface (& the rear wheels have good traction) it should be fine...

Cheers
AnswerID: 451472

Reply By: Member - Bruce C (NSW) - Sunday, Apr 17, 2011 at 07:31

Sunday, Apr 17, 2011 at 07:31
Hi Jason,

I think the centre diff lock on the Prados is a viscous coupling. A silicone based block which expands as the friction factors increase and so pushing the centre clutch into operation. I think the later 80 series and the 100 series use the same.
My 96 80 series has the electrically operated locker and a switch on the dash.

Try reversing a little then going forward a little to get it out as you have proven it is just the diff windup that is holding the clutch in.

It could be that the silicone has deteriorated and needs replacing

Always good to pick up one of those gregories workshop manuals, if they are available for your model, as they are very helpful in understanding how the beasts work even if you do not do your own work on them.

Cheers, Bruce.
At home and at ease on a track that I know not and
restless and lost on a track that I know. HL.

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AnswerID: 451490

Follow Up By: Member - Phil G (SA) - Sunday, Apr 17, 2011 at 08:50

Sunday, Apr 17, 2011 at 08:50
Gday Bruce,
The only Landcruisers with a viscous coupling were the Sahara 80series - everything else (including all Prados) have a conventional centre diff.
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FollowupID: 724115

Reply By: prado-wolf - Thursday, Apr 21, 2011 at 14:17

Thursday, Apr 21, 2011 at 14:17
Hi Jason,

i have a 2002 Prado and i had the same issue , i was so concerned that i decided in birdsville not to do the Simpson but in fact go around to Alice and see the Toyota place there.

What a waste of a trip and so much un neccessary talk , Toyota Alice told me they knew about the issue and like an other guy here suggested showed me to go on a gravel road and disengage and go slowly forward and turn the wheels left to right and back a few times and light comes off.

After that i never got concerned about this anymore and never had an issue with the centre diff.

must just be a glitch.
AnswerID: 451989

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