LC76 1hz front drive locking up

[Brammair]

Morning all,
I have an ‘07 LC76 LX, with auto hubs and fwd/ rear diff lock (standard on the SA models, I think).
Recently it has developed a very unusual problem: with 4H selected all is normal (also easy to select 2H again) until turning sharply left or right. After turning, the front wheels/ drive seem to lock, the vehicle wont freewheel (even down a slope) and drives with difficulty as though something mechanical is engaged resisting movement. Neither forward or rear diff lock is engaged. Also it is then very hard to select 2H again which can only be done by repeatedly driving forward and back many times, preferably the inverse of what got it locked in the first place. Normally 2H/4H is smooth & easy. .
All the above was never the case and seemed to start after our local mechanic here in Malawi (a 75/79 series expert) changed some seals on the gearbox/ transfer case and also replaced L& R hub seals and bearings. He has run out of ideas as to what might be causing the wheels to “lock up”. Up here in Malawi very few vehicles have the dual diff lock and auto hub system. .
Oh yes, as soon as 2H is/ can be selected the “lock up” is gone.
Troubleshooting to date: the hubs have been re-opened but all is in order. I cleaned and checked forward diff function in case it was partially “on” but this is also ok.
Any suggestions for further trouble shooting are appreciated.
Ralph

[CalDriver]

Does this also happen when the front hubs are manually locked? Our cruiser shifts between 2H and 4H much easier when the hubs are locked mannually.

[Brammair]

Yes indeed, normally the 2H/ 4H shift is much smoother when the hubs are manually locked. Unfortunately this doesn’t make a difference to my issue.

[grips]

This sounds like normal axle wind up in a 4x4 with a part time transfer case. Might just be that one of the auto hubs did not engaged and the mechanic have fixed it. Now you experience axle wind up with proper working hubs.

[Chris8d]

This sounds like normal axle wind up in a 4x4 with a part time transfer case. Might just be that one of the auto hubs did not engaged and the mechanic have fixed it. Now you experience axle wind up with proper working hubs.

Exactly my thoughts as well.

I assume all the tyres are of the same size on the vehicle?

[Craig McK]

Does the lock up occur on loose gravel, or are you only 'testing' on tar/hard surfaces?

[Mike N]

Morning all,
I have an ‘07 LC76 LX, with auto hubs and fwd/ rear diff lock (standard on the SA models, I think).
Recently it has developed a very unusual problem: with 4H selected all is normal (also easy to select 2H again) until turning sharply left or right. After turning, the front wheels/ drive seem to lock, the vehicle wont freewheel (even down a slope) and drives with difficulty as though something mechanical is engaged resisting movement. Neither forward or rear diff lock is engaged. Also it is then very hard to select 2H again which can only be done by repeatedly driving forward and back many times, preferably the inverse of what got it locked in the first place. Normally 2H/4H is smooth & easy. .
All the above was never the case and seemed to start after our local mechanic here in Malawi (a 75/79 series expert) changed some seals on the gearbox/ transfer case and also replaced L& R hub seals and bearings. He has run out of ideas as to what might be causing the wheels to “lock up”. Up here in Malawi very few vehicles have the dual diff lock and auto hub system. .
Oh yes, as soon as 2H is/ can be selected the “lock up” is gone.
Troubleshooting to date: the hubs have been re-opened but all is in order. I cleaned and checked forward diff function in case it was partially “on” but this is also ok.
Any suggestions for further trouble shooting are appreciated.
Ralph

This has nothing to do with front hubs, the car does not shift out of 4H into 2H, or alternatively shift itself back into 4H, so the front axle remains connected and auto hubs think they have to engage. Have your shift linkage and transfer case checked, seeing that the mechanic worked there.

[Brammair]

Thanks for the input Gents,

grips: that sounds reasonable, especially as reversing the action that got it locked in the first place seems to undo the trouble. Remedy for this?

Chris8d: yes, tyres all the same size.

CraigMcK: testing mostly in my yard on concrete but tests on gravel result is the same.

MikeN: only shifting 4H back to 2H once „locked“ is near impossible. 2H to 4H is easy/ normal.

Yesterday I decided to let the Toyota dealer here take a look…still waiting for a report back from them.

Thanks again,
Ralph

[sparewheel]

A mate of mine had similar issue V6 SC , he's been around 4x4's for many years so would have felt drivetrain wind up before.

Described exactly that, drive locks up as if something binds, almost as if front and rear diff ratios were not matched. he had it at Toyota (selling dealer) , they first said the same drive train wind up until he drove with them and showed them the problem.

They kept it and replaced a sensor, unfortunately he doesn't know exactly what sensor and they were I think purposely vague, didn't look like they had diffs stripped or even had the wheels off when he got it back a week later. He didn't press them as he was only too happy to get his van back.

PS his had already had a manual hublock conversion done when he bought it at an Automark dealer, worked flawlessly since

[grips]

A mate of mine had similar issue V6 SC , he's been around 4x4's for many years so would have felt drivetrain wind up before.

Described exactly that, drive locks up as if something binds, almost as if front and rear diff ratios were not matched. he had it at Toyota (selling dealer) , they first said the same drive train wind up until he drove with them and showed them the problem.

They kept it and replaced a sensor, unfortunately he doesn't know exactly what sensor and they were I think purposely vague, didn't look like they had diffs stripped or even had the wheels off when he got it back a week later. He didn't press them as he was only too happy to get his van back.

PS his had already had a manual hublock conversion done when he bought it at an Automark dealer, worked flawlessly since

There is no electronics involved on any of the 70 Series drive train. Would be interesting to know what sensor the changed. Even the diff locks are electric operated with switches reading its movement no sensors.
The only other thing I can think of is a diff lock stuck or engaging with out indication. Maybe a faulty diff lock switch. Same switch as on the gearbox reverse light.

[Brammair]

The Toyota team has laid the blame on worn components in the gearbox/ transfer case which they think leads to the wind up/ lock up when 4H is selected. Still waiting for the parts & repair quote .