Auto 'box - what happens when...

[Crispin]

Being bored stuck in traffic, sitting with my foot on the brake, I assume it's just the TC "slipping". What happens if I start to give it some throttle while holding it on the brakes? Does the TC still just "slip", but with obviously more heat being built up by the process? Is there anything mechanical slipping inside?

What happen would break first if I just planted my foot on the throttle and brakes and held it like that?


Just curious...

 

[nivapilot]

She'd hit "stall speed" and stop the engine.

 

[J66P]

you wont break anything as long as you don't do for too long, the way they try an auto for slipping is exactly what you are talking about. Basically if you hold you foot on the brake and floor it you will see what you stall speed is. DO NOT do it for any longer than 10 seconds at a time and leave 30 seconds before doing it again. The oil temperature will increase very very quickly and you will cause damage to the clutch plates if you stall it for too long

I disagree with the above the engine wont stop, or at least it shouldn't

 

[uHu]

Nothing would break, normally. Not until it overheats.
The engine will rev until stall speed, which is around 1800 on my 1hd-fte, + a bit. Then the TC will be too strong for the engine to go any faster. At this situation there is a lot of power generated and most of it is converted to heat in the TC. The tranmission would soon overheat and the ECU would then cut back on engine power, if you have an advanced electronic control. If not that advanced....

Edit: 66 beat me to it

 

[Crispin]

So I've done that, not for long as I was not sure what damage I might be / about to cause. It's also around the 1700-1800 mark and the engine refuses to rev any higher.

When you refer to a clutch, do you mean the one that enages when the TC locks up?

...The oil temperature will increase very very quickly and you will cause damage to the clutch plates if you stall it for too long

Would you be causing damage to the clutch from the heat being generated or because the clutch is slipping? I thought there was no mechanical linkage between input and output except for when the TC locked.

 

[J66P]

you have torque going through thew TC and its stopping in the box, there's clutch plates in the box and its these what will be stopping it driving not the torque convertor

 

[nivapilot]

I stand corrected.....I apologise sirs.

 

[Graham]

She'd hit "stall speed" and stop the engine.

.
Not stop the engine.

Just wont allow it to rev any higher than say 1800 rpm, depending on the serviceability of the auto-box.

Gra.