BigTT

took the TT in for the Haldex service at a local shop. They said that the oil coming out was much thicker than the new stuff going in (which is the correct p/n). He said that it looked like regular gear oil. ( My guess is the dealer that did the last service put in some regular gear oil.. would not put it past them... as they routinely billed Audi for 5qt of oil even when I brought my own in... that is another rant

So my problem is that the Haldex is engaging the rear wheels when backing up and during slow, short radius turns when the car is cold. They verified that the with the car in idle and on the lift, that the rear wheels, are free to spin, but once the car is put into reverse the rear wheel start spinning. This corroborates with my assesment on pavement.

So my question to the brains here, where do I start looking? The shop looked to see if there were any codes, but found none. It sounds like a sensor is non-functional to me. The problem has been going on for several months now.

Any thoughts?


Thanks

T

JohnLZ7W

I'm confused, is Haldex not supposed to work in reverse?

TTschwing

Right from Haldex...

Function-test of the Haldex coupling.

- Rollout in circle

Aim: Check the function of the coupling and the response on the car. Is to be done on level ground.

1. Drive in circle with minimum turning radius at a speed of about 10 km/h.
Disengage the clutch and close the throttle.
Let the car roll to full stop.

2. Drive in circle with minimum turning radius at same speed as in case 1.
Disengage the clutch and run up the engine to 3000 - 4000 rpm.
Let the car roll to full stop.

* If the coupling is working the car will stop in about half the distance in case 2 compared with case 1.

* If there is no difference in the two cases there is a malfunction of the coupling. The problem could be caused by the coupling or by missing signals from the car. A further inspection has to be done to be able to determine the cause of the malfunction.

* If a noise from the HLSC is noticed when turning or driving in circles the oil in the coupling is damaged. The damage can be caused by overheating or by water in the oil.


- AWD test on car lift. (all wheels free to turn.)

Aim: Check the function and the control of the coupling.

1. Pull the handbrake.
Disengage the clutch.
Start the engine.
Put the gearbox in 2:nd gear.
Let the engine idle.
Engage the clutch.

* Engine is supposed to stop when the clutch is engaged. (HLSC controlled as in handbrake start.) If engine do not stop, disengage the hand brake immediately. Otherwise there is a risk of seriously damage on the HLSC.

2. Disengage the handbrake.
Disengage the clutch and start the engine
Put the gearbox in 2:nd gear.
Let the engine idle.
Engage the clutch. At least one front wheel and one rear wheel is supposed to turn.
Pull the handbrake for 2 seconds.

* Front wheel is supposed to turn while the rear wheels are supposed to stop when the brake is pulled. Engine is supposed to run all the time. (HLSC controlled as in handbrake turn.) Don't exceed the 2 seconds or repeat the test for more than 5 times during a 5-minute period. Otherwise there is a risk of seriously damage on the HLSC.


Trouble shooting on HLSC

- Visual inspection

Aim: Check for leakage and external damage that affects the function on the HLSC. Is to be done with the car on a car lift.

1. Check for oil-leakage from the coupling. If leakage is found, check oil level at the level screw on the left side of the coupling.


2. Check wires and connecting sockets.

T8 - Socket between car and control unit
T8/1, Red = Ign.
T8/2, Black = Gnd.
T8/3, White = BLS
T8/4, Blue = HBLS
T8/5, Brown = K-line
T8/7, Blue/Grey = CAN low
T8/8, Blue/Orange = CAN high

T2 - Socket between control unit and feeder pump
T2/1, Yellow = Pump 1
T2/2, Yellow/Black = Pump 2


- Signals

Aim: The following signals from the car affect the function of the HLSC. If one or more of the signals is missing or false the function of the HLSC will be reduced.<ul><li><a href="https://forums.audiworld.com/tt/msgs/1452481.phtml">And in the FAQ</a></li></ul>

TTschwing

The new shop didn't drain the differential instead of the Haldex? This could be an easy mistake to make...

It would also be difficult to put gear oil in a haldex due to the unique way it's filled...

Audiboy

when the car is cold means it's an oil viscosity problem. Maybe change it again to flush out old oil

Audiboy

it should, but only if the front rotate a certain amount. On a lift, I see why the rears should spin

BigTT

reciept lists it as Haldex Diff Fluid p/n G052175A1 3qts. don't know if that is the shops' part number or they stuff they got from Audi.

They also replaced the trasmission fluid as well... along with oil change and a brake flush...

BigTT

* If a noise from the HLSC is noticed when turning or driving in circles the oil in the coupling is damaged. The damage can be caused by overheating or by water in the oil.


Yep, I have that... again only when cold, i.e. overnight. I'll check it out tomorrow to see if the new oil has made a difference.

BigTT

only happens when the unit is cold.

TTagz

3 quarts sounds like a bit more than it takes, should be one tube, 1 qt maybe