Clutch issue ?

[izanagi]

(05-28-2019 09:07 AM)Ivan141 Wrote:  Mine had a bit of drag in neutral as well IIRC, for me it was not enough to move the car though.

In neutral there is no connection between the input and output shaft of the box, but components are spinning close to each other and can transfer some motion
through the thick oil. Did you put in the correct grade of oil and what was the ambient temperature?

I put the correct grade of oil.
By the way I was thinking that the problem would come from the release bearing.

[Bean]

As mentioned before when you are in neutral and no pedal pressed the input shaft will still spin (only pressing the clutch will stop that) so any movement transferred to the rear wheels happens inside the gearbox.
When you changed the gearbox oil did you find any metal particals in the old oil/drain plug?

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[Ivan141]

For what it's worth, the problem will probably dissapear once you get the box up to temperature.

[jondee86]

There is a bit of conflicting information here about the symptoms and
exactly what might be causing this (or these) problems. The shotgun
approach may get to the bottom of the mystery, and so I will throw in
something that fits some of the symptoms

Here is a generic clutch master cylinder diagram that I believe represents
what is found inside the Aisin master cylinder.



When the clutch pedal is operated the piston moves forward closing off
the vent port and applying pressure to the slave cylinder. When the pedal
is released, the piston retracts and uncovers the vent port so that any
excess fluid can return to the reservoir. So far so good = normal operation.

However, if the clutch pedal has been adjusted to raise the pedal and
there is no longer adequate freeplay, the piston may not be able to retract
far enough to uncover the vent port. When this happens, it is possible for
extra fluid to pass by the high pressure seal and enter and become trapped
on the (now sealed) high pressure side of the piston.

Under these circumstances the fluid volume is slowly "ratcheted" up as the
pedal is operated, resulting in the slave piston creeping forward and exerting
pressure on the cltch fork. This will reduce the clamping load exerted by the
clutch, bringing it ever closer to slipping. Eventually, the clutch will be unable
to transmit sufficient torque to drive the car and will burn up.

Simple enough to get under the dash and check the adjustment of the clutch
pedal linkage according to the Toyota Service Manual. Alternative check is to
get under the car and open the slave bleeder screw and see if fluid under
pressure squirts out. If there is trapped pressure the slave will also be pushing
hard against the fork without any freeplay.

Cheers... jondee86

[Ivan141]

Jondee I'm not going to argue about the tech bit, but I dont see how it relates to a car moving while in neutral and not doing so when the clutch is depressed.
If anything the problem you describe would prevent the car from moving at all.

[jondee86]

No problem. As I said, there is conflicting information about this problem and
there may be more than one factor involved. The situation I outlined above
could contribute to the car rolling back from the ramp while in gear, and to
the smell of burning clutch when backing the car out of the garage. It is a
simple matter to check under the car and see if the clutch slave is working
normally. If it is, then one possible cause of the problem is eliminated.

As for the car moving when idling in neutral, I have never heard or
experienced this myself. However, if the car stops moving when the clutch
is disengaged, it is clearly a gearbox related issue. Unfortunately, I know
next to nothing about the inner workings of a gearbox, but it would seem
that there is some small transfer of torque from the countershaft to the
output shaft. Maybe a bent shift fork is holding one half of a synchroniser
in light contact with its matching other part ?

I'll leave that one for the gearbox experts

Cheers... jondee86

PS: And yes, it is not unusual for the viscous drag and internal friction of
the moving parts inside the gearbox to cause the rear wheels to spin with
the rear wheels off the ground. The torque transmitted to the driveshaft
is multiplied by the diff ratio and becomes sufficient to overcome the
friction of the differential and wheel bearings.

But when the vehicle is on its wheels on level ground, the rolling resistance
of the tires is far greater, and (under normal circumstances) the tiny
amount of torque being sent to the rear wheels is no way enough to roll
the car forward at idle.

[banpei]

(06-01-2019 10:46 AM)jondee86 Wrote:  PS: And yes, it is not unusual for the viscous drag and internal friction of
the moving parts inside the gearbox to cause the rear wheels to spin with
the rear wheels off the ground. The torque transmitted to the driveshaft
is multiplied by the diff ratio and becomes sufficient to overcome the
friction of the differential and wheel bearings.

But when the vehicle is on its wheels on level ground, the rolling resistance
of the tires is far greater, and (under normal circumstances) the tiny
amount of torque being sent to the rear wheels is no way enough to roll
the car forward at idle.

Because a picture/video is way more clear than words, forward to 8:36 in this video:

But yes, this is most probably not the issue that has been described here.

[izanagi]

Some news.
Yesterday I checked the freeplay of the pedal and adjusted everything around this. According to the factory service manual.
I also blended the clutch slave.
Now the clutch disk seems to "disconnect" correctly and I stopped smelling burn.
While I was bleeding I saw some dirt inside brake fluid. Maybe that was the problem.
Now the car is still moving in neutral.
I guess it come from the gearbox but I used stock oil gearbox.

[Power_uP]

It think you'll have to take the gearbox out and rebuild. Having thought about it, my original post is BS, and I'm pretty sure there's absolutely nothing wrong with your clutch.

Let me know if you need another gearbox, I may still have a T50 in the shed.

[izanagi]

(06-03-2019 04:47 PM)Power_uP Wrote:  It think you'll have to take the gearbox out and rebuild. Having thought about it, my original post is BS, and I'm pretty sure there's absolutely nothing wrong with your clutch.

Let me know if you need another gearbox, I may still have a T50 in the shed.

Shipping a gearbox to Belgium would be expensive.