Transfer case
12-19-2019, 11:39 PM
#841
Three Wheelin'
Doug,
Unless you have limited slip or PTV (Porsche torque vectoring - aka - computer-controlled torque-distribution on the rear diff) I can't begin to fathom why adding a slip-lock additive to a differential would make ANY difference at all.
There is no clutch in an open differential, and that's what the vast majority of Cayennes are equipped with. Porsche decided they could use electronic control of the brake system to provide the same benefits (and more, better) than mechanical limited-slip differentials could and at the same time eliminate the complexity, cost, and weight of limited-slip diffs. The only reason they use a clutch-type differential in the PTV is to computer control distribution of torque on the rear wheels. the computer tells the differential to put more torque on the outside wheel in a turn, effectively pushing the car around the turn. And if you do have PTV - I suspect adding slip to the differential is exactly the wrong thing to do since the car's computer is counting on a certain torque-force pushing the car into a turn, coming from the rear outside wheel. Having less power there would probably result in going wide in a corner unless the computer and differential can compensate for the change in clutch friction.
I use straight 75W-90 GL5 in my differentials, and they've been trouble-free for an awfully long time.
Unless you have limited slip or PTV (Porsche torque vectoring - aka - computer-controlled torque-distribution on the rear diff) I can't begin to fathom why adding a slip-lock additive to a differential would make ANY difference at all.
There is no clutch in an open differential, and that's what the vast majority of Cayennes are equipped with. Porsche decided they could use electronic control of the brake system to provide the same benefits (and more, better) than mechanical limited-slip differentials could and at the same time eliminate the complexity, cost, and weight of limited-slip diffs. The only reason they use a clutch-type differential in the PTV is to computer control distribution of torque on the rear wheels. the computer tells the differential to put more torque on the outside wheel in a turn, effectively pushing the car around the turn. And if you do have PTV - I suspect adding slip to the differential is exactly the wrong thing to do since the car's computer is counting on a certain torque-force pushing the car into a turn, coming from the rear outside wheel. Having less power there would probably result in going wide in a corner unless the computer and differential can compensate for the change in clutch friction.
I use straight 75W-90 GL5 in my differentials, and they've been trouble-free for an awfully long time.
12-20-2019, 12:03 AM
#842
Banned
Join Date: Mar 2011
Location: Spring Lake, NJ, US of A
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I'd guess PTV is maybe 5-10% of Cayenne's sold. And while it is a clutch differential, it's not actually a limited-slip differential. Those are strictly mechanical. I do know some people with PTV's have had issues with them behaving badly - snapping and crackling around corners - so if that happens - some slip additive might be an answer, but I don't think I would just add it. I would be inclined to change the oil more frequently than recommended and make sure to use the special oil type Porsche spec's (I'd guess it has some slip additive as part of it's formula.)
12-20-2019, 01:37 PM
#843
So when you are in the tight turning conditions and have the tight feeling, would just a change of new diff. oil correct this noise and feel? Would you change both front and rear?
I have 74k miles on it and I don't believe the diff oil has ever been changed.
Also, I changed the TC fluid with friction modifier mix and it fixed my condition. This year should I just change fluid only if I currently have no issues? Or replace again with friction mod. fluid and TC fluid?
Thanks,
Mike
I have 74k miles on it and I don't believe the diff oil has ever been changed.
Also, I changed the TC fluid with friction modifier mix and it fixed my condition. This year should I just change fluid only if I currently have no issues? Or replace again with friction mod. fluid and TC fluid?
Thanks,
Mike
12-21-2019, 07:48 PM
#844
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Location: Spring Lake, NJ, US of A
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So when you are in the tight turning conditions and have the tight feeling, would just a change of new diff. oil correct this noise and feel? Would you change both front and rear?
I have 74k miles on it and I don't believe the diff oil has ever been changed.
Also, I changed the TC fluid with friction modifier mix and it fixed my condition. This year should I just change fluid only if I currently have no issues? Or replace again with friction mod. fluid and TC fluid?
Thanks,
Mike
I have 74k miles on it and I don't believe the diff oil has ever been changed.
Also, I changed the TC fluid with friction modifier mix and it fixed my condition. This year should I just change fluid only if I currently have no issues? Or replace again with friction mod. fluid and TC fluid?
Thanks,
Mike
I'm not certain what you mean by "tight feeling" - almost all cars feel heavier on a very sharp radius turn with the steering wheel on full lock. Unless you have Porsche Torque Vectoring aka PTV (unlikely) - changing the differential fluid won't make a lot of difference in that feeling. It's certainly not a bad idea to change the differential oils.. make sure you're using the correct oil. If you have PTV - then the rear differential uses a different kind of oil. If not - both front and back should be happy with GL4/5 75W90 synthetic gear oil.
12-21-2019, 11:49 PM
#845
I just had my 60k mile service done at the stealerrship. One of the things they recommended was the TC fluid. Seems like they have been notified to recommend it. I have a diesel but had TC exchanged on 11/2017 @33k miles
01-02-2020, 06:36 PM
#846
how much did the stealerrship quote you to preform the service?
01-02-2020, 06:48 PM
#847
So last month the dealer installed a new transfer case in my 12 CTT. However this did not get rid of the noise it was making so another trip to the dealer. Now what they are telling me is they are replacing the line holder bushings for the PDCC. It appears that the grinding noise is from the vibration of PDCC lines vibrating when pressure is run through it. Who knew. I should have it back in a couple of days.
01-03-2020, 06:11 AM
#848
01-05-2020, 05:59 PM
#849
Even at MSRP Transfer Case oil is 75$ - https://www.suncoastparts.com/product/SKUTRAN.html
01-06-2020, 02:42 PM
#850
180$ in parts WTF ?
Even at MSRP Transfer Case oil is 75$ - https://www.suncoastparts.com/product/SKUTRAN.html
Even at MSRP Transfer Case oil is 75$ - https://www.suncoastparts.com/product/SKUTRAN.html
01-06-2020, 02:45 PM
#851
180$ in parts WTF ?
Even at MSRP Transfer Case oil is 75$ - https://www.suncoastparts.com/product/SKUTRAN.html
Even at MSRP Transfer Case oil is 75$ - https://www.suncoastparts.com/product/SKUTRAN.html
so a $100 plastic part for a Porsche sounds about right
01-06-2020, 03:11 PM
#852
01-06-2020, 03:15 PM
#853
here is the video - comparison is at 1:10 mark
01-06-2020, 03:34 PM
#854
I have an update on my most resent post. The dealer replaced the bushing for the PDCC lines that they said were causing vibration. Well after picking up my car and driving to my office, the noise was still there but now as pronounced and seem to be coming from the rear end. So I had a technician drive it and fortunately it made the grinding sounds from the rear end. Now they are saying that it is the differential. It does have PTV. They told me 5-6 weeks for a new diff to come from Germany. So thankful for the CPO warranty.
01-06-2020, 03:37 PM
#855
I have an update on my most resent post. The dealer replaced the bushing for the PDCC lines that they said were causing vibration. Well after picking up my car and driving to my office, the noise was still there but now as pronounced and seem to be coming from the rear end. So I had a technician drive it and fortunately it made the grinding sounds from the rear end. Now they are saying that it is the differential. It does have PTV. They told me 5-6 weeks for a new diff to come from Germany. So thankful for the CPO warranty.