Prado 120 out of sink

Submitted: Wednesday, Jun 28, 2006 at 10:16
ThreadID: 35356 Views:1738 Replies:7 FollowUps:4
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Did a trip to Robe last week and then up to Mildura and then back home to near Geelong.
While at Robe we did some beach driving and while doing so noticed the back wheels of our Prado driving quicker than the front wheels. Because of this I couldn't keep the back wheels in the same track as the front wheels and needless to say, because of this we got bogged a few times!
My brother in law's got an older discovery with automatic (mine's a manual) and he had no trouble going through the sand. I had to go flat out in low second and he just crawled along.
I know automatics are a great advantage in sand but i still think my main problem was crabbing through the sand. I've also noticed it doing this in mud on the farm, when we use to have rain!
On passed trips this hasn't been as noticeable when pulling a trak shak?
Having spoken to a mechanic at Mildura he asked me what sort of tyres I had and I said slightly worn out grandtracks. And his comment was 'there's your answer, with those useless tyres you track everywhere.'
Is this the answer? Or have i got a problem with the syncronisation of front and back wheels driving?
Brother in law who works for the DSE said he found similar problems with two late model prado's in mud.
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Reply By: Redback - Wednesday, Jun 28, 2006 at 10:45

Wednesday, Jun 28, 2006 at 10:45
I'd say it's a combination of things, to heavy on the right foot, incorrect pressures, bad tyre choice, too low a gear.

Discos are good in the sand anyway, even better if it's the Disco 2, traction control works brilliant in the Disco2 when in sand.

Baz.
AnswerID: 180795

Follow Up By: Lachie - Wednesday, Jun 28, 2006 at 13:29

Wednesday, Jun 28, 2006 at 13:29
Tyre pressure was 15psi. If I was in third the prado would just die. Thats why the automatic is better.The prado is a TD
I have been driving for 35 years with various 4wd and haven't come across this before .
I thought the less agressive tyre tread was better in the sand ??
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FollowupID: 437105

Follow Up By: Redback - Wednesday, Jun 28, 2006 at 14:20

Wednesday, Jun 28, 2006 at 14:20
Try string lining to see if it's crabbing or go into a carpark and park your driverside whell parralell to the line then measure the distance from your back and front passenger side wheels to the other line, surely it should be noticable when driving on the blacktop too, and aspecially when towing, also if it is crabbing drive on a flat road and let go of the wheel should pull to one side.

Other than this, refer to my previous comments or maybe a weight thing but i don't think the Prado is any heavier than a Disco..

Baz.
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FollowupID: 437113

Follow Up By: Lachie - Wednesday, Jun 28, 2006 at 16:05

Wednesday, Jun 28, 2006 at 16:05
Thanks I will try the things you Suggested.
I have rang Toyota and they said they would ask around. The man I spoke to said if all the wheels had equal wear everything should be ok,which thery are.
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FollowupID: 437133

Reply By: mick - Wednesday, Jun 28, 2006 at 11:13

Wednesday, Jun 28, 2006 at 11:13
Different levels of traction/ tyre wear from front to rear tyres perhaps.

Mick
AnswerID: 180800

Reply By: Frank_Troopy - Wednesday, Jun 28, 2006 at 13:17

Wednesday, Jun 28, 2006 at 13:17
Hi,
Pardon my ignorance; does the Prado not have a centre diff lock? Surely it does. If the centre diff is locked, the front and rear drive shafts must be driven at the same speed.

Maybe the knob, button, auto-slip-sensing gizmo or whatever engages the centre lock is not working.

Cheers Frank.
AnswerID: 180816

Reply By: Member - Ed. C.- Wednesday, Jun 28, 2006 at 14:38

Wednesday, Jun 28, 2006 at 14:38
I'm not familiar with the Prado..

Do these have a viscous(sp?) coupling (centre diff)???

If so, I'd be gettin' that checked out.....
Confucius say.....
"He who lie underneath automobile with tool in hand,
....Not necessarily mechanic!!"

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AnswerID: 180828

Reply By: Member - Phil G (SA) - Wednesday, Jun 28, 2006 at 21:51

Wednesday, Jun 28, 2006 at 21:51
I'm with Frank on this one. If the centre diff is locked (as it should in sand), theres no way the front and rear can turn at different speeds. Sounds to me like you didn't have it locked.

Grandtreks are a great sand tyre.
AnswerID: 180929

Follow Up By: Lachie - Thursday, Jun 29, 2006 at 09:53

Thursday, Jun 29, 2006 at 09:53
If it is in low range how is it not locked ?
The man from toyota I rang said he thought one chain drove the back and front wheels when 4wd H OR LOW was engaged. He was going to ask around and get back to me.
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FollowupID: 437271

Reply By: Member - Andrew W (SA) - Thursday, Jun 29, 2006 at 13:27

Thursday, Jun 29, 2006 at 13:27
with a limited slip diff in the rear, all it takes is for significant difference in traction between left and right and one will drive more than the other.

the centre diff is a limited slip diff too, so you can end up with a situation where you are not really driving much at all ...

Doesn't seem that unusual for a 120 series to me ...
AnswerID: 181023

Reply By: Lachie - Thursday, Jun 29, 2006 at 15:49

Thursday, Jun 29, 2006 at 15:49
Toyota rang back and said this is not unusual ( ??? ) The ratio of drive is 60% rear and 40 % front. When things get tougher the the drive goes to the wheel with the most slipage.

It still doesn,t make sence to me. You should still have a 4wd that all wheels drive at nearly the same speed under tough going.

What were the drive ratios of the older type of 4wds where you had to lock the hups in etc.? I know I never had the trouble with the older types.
AnswerID: 181050

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