boostdr

2011 176kw CD, 216,000km

****Initially thought it was the transmission but turned out to be the front Differential ****

I recently started to experience a harsh shudder only when under heavy load and in low gears. The shudder was a loud hammer sound and quite low frequency. Like 5 hammers in 2s. Sound seemed to be originating from forward of the driver(right) at the back of the engine. I originally thought it was a loud ABS unit activating for traction control. The problem over 3 days got more and more sensitive to load. The shudder wasn’t as
severe but the frequency increased to say 20 small hammers in 2s which gave more slipping. Got to the stage I had to accelerate extremely gently. This evening I was 500m from home and lost all drive from the transmission. When in drive it makes a slight grinding noise. When it’s out in park from drive it makes a ratcheting sound similar to if you put the car in park while it’s still moving.

Initial thoughts are a loss of transmission oil pressure. Maybe a blocked filter, failed oil pump, I’m not sure. Will pull the pan off tomorrow Aussie time and inspect.

Does this sound familiar to anyone ? Common type of problem? ..Or have I been unlucky to have bought a worn out CD.

Matt

Quadcammer

could be the transfer case, but from a distance its hard to diagnose.

good luck pulling it apart.

boostdr

Would the transfer case lose all drive and make a noise at idle ?

Quadcammer

It shouldn't lose all drive mechanically, but from an electronic standpoint, if its not seeing drive sent to front wheels, who knows what might freak out.

Probably shouldn't make a noise in idle, I must have missed that.

You might be right that its a tranny issue, but they seem to be robust so who knows.

drdantheman1

Yes, a transfer case failure would absolutely present that way. Has your TC ever been replaced? The Japanese built Aisin transmission in the cayenne is very stout, I'd be surprised if that's the origin of failure.

boostdr

TC hasn’t been replaced. I recently changed the fluids and didn’t notice anything abnormal.

The previous owner did tow a ski boat quite a bit so it may have had a hard life.

boostdr

Those who said it may not be the transmission were correct....however it wasn’t the TC it was the front differential.

boostdr

Looks like the front differential ring gear has separated from the housing.

part number of the internal diff is: ZF 4460 360 341 0P 4J F

and the front differential assembly is: 0BM409505L MUN

ratio: 3.27

From what I can see the ring gear is welded to the housing rather than bolted and probably failed. I have endoscope video but it won’t load.

Does anyone have a reference to the new part? Seems the differential inner workings of this part number were discontinued in 2014.

boostdr

Turns out the failed weld prediction was correct

garrett376

Really great work! How did you keep the engine/trans suspended? The engine mounts must have a separate frame from the suspension?

boostdr

Engine and trans have their own support. Sub-frame is only for the front differential, lower control arms, steering rack and sway bar

workshop manual: Link to 958 workshop manual

garrett376

Your threaded holders are brilliant, too. Great job.

CAVU

Looks like the original weld may have been an inertia friction weld.

Looking at a replacement diff from a breaker or looking at a rebuilt or seeing if a part is available ( https://www.progearandtransmission.c...-differentials but much closer to you of course)?

boostdr

I agree looks like a friction weld. My theory is there is a key way also. The weld not being completely structural. Wear on the teeth was virtually non existent.

found a couple of replacements. One from a Touareg (61K km) and one from a Cayenne (82K km) both under $1,000AUD

911-997

Why would this fail?