PaulW

So we talk about torque converters all the time.....but here are some pictures of one taken apart.

Was at Eddie's transmission shop yesterday.....will be putting the new speed sensor in tonight, and will see if anything changes or not.

Okay.....here is a torque converter.....this is the transmission side, the cut out drives the oil pump, and the input shaft to the transmission fits into the middle.

The other side of the torque converter has three brackets that allow it to be bolted to the flywheel. This is done by removing the starter to get to the forward part of the flywheel.

<img src="http://www.audipages.com/Tech_Articles/auto_transmission/sm_DSCN1343.JPG">

Here is one apart (out of a BMW X5 that failed, you can see it's all bent up on the vanes), it is split in two:

<img src="http://www.audipages.com/Tech_Articles/auto_transmission/torqueconverter2.JPG">

<img src="http://www.audipages.com/Tech_Articles/auto_transmission/torqueconverter1.JPG">

Here is the description on how it works.....

<img src="http://www.audipages.com/Tech_Articles/auto_transmission/torqueconverter3.JPG">
<img src="http://www.audipages.com/Tech_Articles/auto_transmission/torqueconverter4.JPG">

It locks the shaft by porting oil to the large face of the torque converter and presses it hard against the casing. See second picture above. That big plate moves relative to the casing (not easily, but it does). There is clutch material between that plate and the housing.

When hydraulic pressure is pressed against the plate, it locks it hard up against the housing and locks the torque converter. It no longer creates heat and you get better fuel economy.

If you are wondering how it gets oil up there, all the shafts are hollow and have port holes drilled in them with seals that allows hydraulic fluid (ATF) to be ported to all of these parts (including returns).

Hopefully everything above is accurate, but since this is my understanding of it, I might not be correct. Please comment if I'm not.

BTW, when you send this out for rebuild, it is cut open, inspected, change any bearings in there, replace the clutch material, put the two halfs back together, weld it up and balance it.

It is then painted so you know it was rebuilt.

PaulW

There is really nothing in there to go wrong.

In order for it not to lock up with hydrualic pressure pushing against it, the clutch would have to be slipping. But vag-com says it's not locked.....so it's not sending a signal to lock it.

It has to be either a loss of hydraulic pressure somewhere or.....

The TCU is telling the valve body to not lock it up, and considering the only thing that changes is throttle position when it drops out of lock up, I would have to think it is one of the inputs. The hydraulic pressure of the pump is exactly the same at any given motor RPM regardless of TC lock up or not, it is driven by the engine flywheel through the torque converter housing to the two little teeth.

So it's either one of the input sensors or the valve body (which only gets it signal from the TCU). So I'm thinking it's a signal to the TCU.

We'll see.

Marco said a rebuilt torque converter solved his problem......hmmm....

ttuling

then any stickiness in how the "big plate moves relative to the casing" might cause the TCM to command hunting as it searches for the desired slip rpm. Imagine you've moved the throttle such that the TCM releases a little pressure to take the clutch from fully to partially locked, but the sticky big plate doesn't move. The TCM drops the pressure some more, then bang, the clutch unlocks. That wasn't what the TCM wanted, so it increases lockup pressure. The big plate sticks again. It increases pressure some more. Bang, it moves, but locks up too much. Repeat.

The same mechanism could explain the trailing throttle dropout followed by thumping reengagement. The TCM's just trying for some slip (as we know, from VAG-COM, that it does when coasting without braking at speed).

But it doesn't have to be a sticky clutch to do this. A sticky electrovalve for the converter lockup pressure, or sticky spool valves in the valve body, could do it. This is why I have no trouble believing that a new converter did the trick in one case, and a valve body was the culprit in another. If the TCM gets sticky, delayed responses to its commands to change how much the converter clutch is (or isn't) slipping, what's to keep it from commanding overreactions that lead to it hunting forever between too much and too little slip?

If ever you feel it hunting without corresponding variations in N218 current, none of the above applies.

Tom

airbil

..and sorry if this has been answered ad nauseum.
But where do all the metal flakes stuck to the magnets come from... is it the gears or the TC or somewhere else?
I have heard second hand but from a reliable source that the TC is usually the problem for whatever hearsay that may be worth

PaulW

It spins round and round, it just wears down the parts.....if you saw one apart, you could see it too.

poly

How is the front differential? Any PICs? Is it a torsen as well?

aron56

Hi Paul, with quote to your post, i just wanted to know where is the torque converter location. It seems that each time you renew the fluid, you would have to release the old fluid from the torque converter too which would avoid you to overfill the fluid while you put in the fresh new ATF oil.

I was told that at the torque converter housing there should be a drain plug. But the thing is, where is the said torque converter location? Hope you could advise me...

Im using a 1995, Audi 100 2.6E V6

Thanks.
Aron