Wildbear

Recurring rear diff lock fault on a 2012 CTT

Simple fix....changed fluid and used Castrol 75-90 Syntrax limited slip synthetic
Voila!!

1999Aero911

Did you also have a noise sometime coming from the rear while turning? My 2012 CTT with the PTV Rear Diff still makes the clunk after a transfer case replacement (although it doesn't seem to do it as often now). I changed the fluid with Motul 300LS but might need to add some friction modifier or change the fluid again since when I did them last winter at 120k miles none of the diff fluids had ever been serviced before.

Wildbear

Very slight noise which is pretty standard for limited slip. But no clunks.
I'd sure change it again as it is super easy.
Try the same fluid I used....Castrol 75-90 Syntrax limited slip synthetic. Got it off Amazon.
Buy two litres.
I know someone used Ravenol and the fault warning started after he switched to that.
went to the Castrol and it went away.
go figure :/

maxspeeds

I recently changed the rear PTV differential on my Turbo to the Motul 75W-90 300LS Synthetic oil and after approx 100 miles, i am getting the "Differential Fault Lock" error with the red triangle on the rear diff. How is the Motul 300LS working for you? Have you tried the Castrol 75-90 Syntrax limited slip synthetic or a different type of fluid?

Gus B.

For future reference sake, the rear diffs in mention are PVT+ versions or regular differential?

garrett376

Can you pull the code that is present and report back?

I've run Motul 300LS, Ravenol MDL, and factory oil in the rear PTV+ differentials for many years including lots of off-road driving, with no issues.

maxspeeds

Yep, I can pull the code tonight after work with my Launch X431. Strange thing is the fault does not always come up consistently. It seems it comes up about 50% of the time and there is no difference in driving with no binding being heard or felt.

1999Aero911

I would say changing the fluid (which looked like it had never changed) with 300LS didn't really change anything with the car. Even getting the TC replaced wasn't a huge change. Still has the clunk in turns. Seems to be less loud / occur less than before the new TC. Did you make sure you added enough fluid to the rear diff? Some people said that they couldn't get a full qt in without rotating the tires a few revolutions. Personally, I got almost 1.5qts in there without needing to do that.

Changing the rear diff fluid again with a different brand will be something I do this winter, since it isn't that expensive and can only help.

maxspeeds

This thread is only on Cayennes with PTV+ rear differentials.

maxspeeds

I added 1.4 L of 300LS to the rear diff. The trick is to insert the fluid transfer pump hose deep into the diff to get the full amount pumped in. For me, the new oil helped to significantly quiet the walnut crunch sound on sharp left turns from a stop. My car drives better than it ever has except for this "fault differential lock" that occasionally pops up. And, it started appearing approx 100 miles after the fluid change. It never appeared previously on the old fluid even when the rear diff would make loud crunching noises.

Gus B.

My bad, did not get the memo where this was clearly stated. I do know that the 958 Turbo and GTS come with two types of rear differentials and the PTV+ does require a specific type of fluid that is different from the regular differential. Was just trying to confirm what type of differential the OP has to make sure others don't make the mistake of using the wrong fluid type.

garrett376

There are no electronics associated with the standard differential so there will never be a Rear Differential Fault in the instrument cluster with a non-PTV+ differential.

cring001

@Wildbear Did this error come back? I was having differential fault intermittent 1or 2 times first 6 months since I purchased my 2012 CTT in February but it started to get more frequent once every 5-7 trips yet would go off after driving a bit. Then I changed the fluid in rear diff (used liqui moly 75w90 ) and it is on every time now.
Wondering if your "fix" remained.

Franko T

Mine is on and off every trip. Super annoying. I pulled the fuses 3 and 4 to disable it for some time and there was no crunch noises anymore. I've tried fluid changes as well. My electric motor is probably worn out and not worth putting a OEM in there. I'm trying to figure out if this stupid PTV plus can be coded put.

garrett376

Send me your differential and I can make the crunching go away...