PTV+ locking increase with PSM switched off
01-03-2018, 08:28 PM
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PTV+ locking increase with PSM switched off
So I have this new-to-me 2011 CTT with PTV+. Transfer case has already been replaced once at some point. Currently the car has 75k miles.
I was noticing a bit of noise/binding at parking lot speeds but none of the usual hesitation or clicking reported for TC failures.
Today I swapped the tc fluid but it had actually just been changed by the PO so nothing to see there. I also did the rear diff- it was black of course, and probably original.
I replaced the oil with SWEPCO 201 since I've had good experiences with it in limited slip diffs in the past. The car now doesn't make any noises except under one specific condition: the PSM is switched off turning at low speeds
If i slowly drive back back and forth in a parking lot, it seems like the rear diff is locking up the instant I turn off psm and releasing when I turn it back on.
this makes sense to me since you would want more diff locking if you were: on track, stuck in snow or sand, or hooning the car. All times when you might turn off PSM.
I was noticing a bit of noise/binding at parking lot speeds but none of the usual hesitation or clicking reported for TC failures.
Today I swapped the tc fluid but it had actually just been changed by the PO so nothing to see there. I also did the rear diff- it was black of course, and probably original.
I replaced the oil with SWEPCO 201 since I've had good experiences with it in limited slip diffs in the past. The car now doesn't make any noises except under one specific condition: the PSM is switched off turning at low speeds
If i slowly drive back back and forth in a parking lot, it seems like the rear diff is locking up the instant I turn off psm and releasing when I turn it back on.
this makes sense to me since you would want more diff locking if you were: on track, stuck in snow or sand, or hooning the car. All times when you might turn off PSM.
01-03-2018, 11:03 PM
#2
Drifting
I think what you're hearing is normal having PTV +. Do you also have PDCC ?
I changed the rear and front differential fluid with the OEM stuff, 90% of the noise went away.
I only had the issue when taking off from a stop and the initial stage of accelerating when turning left or right.
I will flush again in another 1,000 miles and see if i can improve with less noise.
I changed the rear and front differential fluid with the OEM stuff, 90% of the noise went away.
I only had the issue when taking off from a stop and the initial stage of accelerating when turning left or right.
I will flush again in another 1,000 miles and see if i can improve with less noise.
01-04-2018, 01:01 PM
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Yes I also have PDCC, and yes that is the only time I hear any noise as well- at very slow speeds.
Glad to hear your experience was similar and that it is "normal."
Glad to hear your experience was similar and that it is "normal."
01-04-2018, 06:03 PM
#4
Drifting
https://rennlist.com/forums/cayenne-...l#post14660084
01-05-2018, 07:50 AM
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Re-reading my post I see I was a little vague...when I got the car it was making a bit of noise at random times, moreso at parking lot speeds. I replaced the rear diff oil with SWEPCO 201 and that resolved all the noises with the exception of the PSM off parking lot speeds noises when turning, which it seems are normal for PTV+ due to the increased locking with PSM off. I also replaced the transaxle oil, but the PO had already put some fresh Ravenol in so that was sort of a non-issue.
I haven't done the front yet but that is next on the list. I have a short 8mm hex wrench just for the purpose of that plug. I'll be putting SWEPCO 201 in the front diff as well.
I haven't done the front yet but that is next on the list. I have a short 8mm hex wrench just for the purpose of that plug. I'll be putting SWEPCO 201 in the front diff as well.
01-18-2018, 10:50 AM
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PTV+ definitely making noise:
1) when cold, during the first turn from a stop (like turning at an intersection
2) in parking lots with PSM off
3) driving aggressively, especially with PSM off
4) in any of the off-road modes (I activated them in some sand, not on pavement...I'm not THAT dumb)
But, that being said, diffs can make noise. And no metal came out when I did the fluid. And it seems to be working *very* well because the car is much more fun to thrash and feels very RWD, especially compared to the old 955.
In conclusion, I am going to continue to let it makes as much noise as it damn well pleases, change the rear diff fluid at least once a year, and keep on trucking.
If it's gonna break, it's gonna break. I have budgeted for the part, and changing a rear diff on a cayenne is pretty easy (been there, done that). But I think it'll be fine.
1) when cold, during the first turn from a stop (like turning at an intersection
2) in parking lots with PSM off
3) driving aggressively, especially with PSM off
4) in any of the off-road modes (I activated them in some sand, not on pavement...I'm not THAT dumb)
But, that being said, diffs can make noise. And no metal came out when I did the fluid. And it seems to be working *very* well because the car is much more fun to thrash and feels very RWD, especially compared to the old 955.
In conclusion, I am going to continue to let it makes as much noise as it damn well pleases, change the rear diff fluid at least once a year, and keep on trucking.
If it's gonna break, it's gonna break. I have budgeted for the part, and changing a rear diff on a cayenne is pretty easy (been there, done that). But I think it'll be fine.
01-18-2018, 12:14 PM
#7
Drifting
I think what you're hearing is normal having PTV +. Do you also have PDCC ?
I changed the rear and front differential fluid with the OEM stuff, 90% of the noise went away.
I only had the issue when taking off from a stop and the initial stage of accelerating when turning left or right.
I will flush again in another 1,000 miles and see if i can improve with less noise.
I changed the rear and front differential fluid with the OEM stuff, 90% of the noise went away.
I only had the issue when taking off from a stop and the initial stage of accelerating when turning left or right.
I will flush again in another 1,000 miles and see if i can improve with less noise.
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01-20-2018, 12:27 AM
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01-24-2018, 08:15 AM
#11
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you guys are probably tired of me posting about this, but an updated:
Finally got it out on the beach. Off-road mode, especially locking the center and rear diffs, it definitely made some noise at first. But once it "locked in" or whatever, all the noise stopped and it was fine.
I really think the PTV+ suffers the same issue that the stepper motor did on the Gen 1 Cayenne transfer case: lack of use causes it to get sticky.
No one buys a new 2011 CTT and then takes it to the beach and locks the diffs...ever. Just like no one used low range on the old cayennes and that caused the stepper motors to gum up.
I'm going to keep driving it (spiritedly) and taking it on the beach to lock diffs when I can, and then change fluids again and see how they look. I may even go so far as to clean the stepper motor connector or even remove it from the diff for inspection/lubrication. It doesn't seem to be the diff making noise, it's changes in the mode of the diff that makes noise.
Finally got it out on the beach. Off-road mode, especially locking the center and rear diffs, it definitely made some noise at first. But once it "locked in" or whatever, all the noise stopped and it was fine.
I really think the PTV+ suffers the same issue that the stepper motor did on the Gen 1 Cayenne transfer case: lack of use causes it to get sticky.
No one buys a new 2011 CTT and then takes it to the beach and locks the diffs...ever. Just like no one used low range on the old cayennes and that caused the stepper motors to gum up.
I'm going to keep driving it (spiritedly) and taking it on the beach to lock diffs when I can, and then change fluids again and see how they look. I may even go so far as to clean the stepper motor connector or even remove it from the diff for inspection/lubrication. It doesn't seem to be the diff making noise, it's changes in the mode of the diff that makes noise.
01-24-2018, 12:59 PM
#12
Drifting
Thanks for the update. I'll try that myself. My family has a ranch i can play with the locking differential.
Also an update from myself. I installed new tires and noise has been further reduced.
Wear on the old tires: Fronts had 10% life, rears had 12-14% life. I doubt such small margins have an impact however who knows.
Also an update from myself. I installed new tires and noise has been further reduced.
Wear on the old tires: Fronts had 10% life, rears had 12-14% life. I doubt such small margins have an impact however who knows.
01-25-2018, 04:06 PM
#14
Drifting
you guys are probably tired of me posting about this, but an updated:
Finally got it out on the beach. Off-road mode, especially locking the center and rear diffs, it definitely made some noise at first. But once it "locked in" or whatever, all the noise stopped and it was fine.
I really think the PTV+ suffers the same issue that the stepper motor did on the Gen 1 Cayenne transfer case: lack of use causes it to get sticky.
No one buys a new 2011 CTT and then takes it to the beach and locks the diffs...ever. Just like no one used low range on the old cayennes and that caused the stepper motors to gum up.
I'm going to keep driving it (spiritedly) and taking it on the beach to lock diffs when I can, and then change fluids again and see how they look. I may even go so far as to clean the stepper motor connector or even remove it from the diff for inspection/lubrication. It doesn't seem to be the diff making noise, it's changes in the mode of the diff that makes noise.
Finally got it out on the beach. Off-road mode, especially locking the center and rear diffs, it definitely made some noise at first. But once it "locked in" or whatever, all the noise stopped and it was fine.
I really think the PTV+ suffers the same issue that the stepper motor did on the Gen 1 Cayenne transfer case: lack of use causes it to get sticky.
No one buys a new 2011 CTT and then takes it to the beach and locks the diffs...ever. Just like no one used low range on the old cayennes and that caused the stepper motors to gum up.
I'm going to keep driving it (spiritedly) and taking it on the beach to lock diffs when I can, and then change fluids again and see how they look. I may even go so far as to clean the stepper motor connector or even remove it from the diff for inspection/lubrication. It doesn't seem to be the diff making noise, it's changes in the mode of the diff that makes noise.
So when I arrived home today, I sat in the cul-de-sac and set it in the most aggressive off-road mode locking the center and rear diffs. Drove up and down our street under 20mph and it was fine with no unusual noise or binding/chattering from the diffs. However when turning in circles in the cul-de-sac with the diffs locked, there was definitely some differential ‘chattering’ when turning tightly at slow speeds. As I lessened the angle at which I was turning, the diff chattering also lessened until at a certain (more normal) turning radius, it went away. That makes sense and seems normal to me, given that when these diffs are locked, they’re acting like an old positraction differential as opposed to a limited-slip unit. And if you’ve ever driven, say, an old domestic muscle car with a true positraction locking differential (like a Detroit Locker), it chatters like crazy in tight turns because the tires are trying to rotate at different rates, which goes against the diff locking them to rotate at the same rate.
So again, I think this behavior in the PTV+ (locking rear diff) equipped Cayennes is the nature of the beast, even the slight slow speed left turn chattering we sometimes experience in the ‘regular’ on-road driving mode.
Last edited by CarGuyNVA; 01-25-2018 at 04:07 PM. Reason: spelling
01-25-2018, 04:48 PM
#15
Rennlist Member
It's never a good plan to use locking modes on anything other than loose surfaces, at any speeds. Sand, snow, mud, gravel, but never dry pavement. Straight lines, maybe or broad sweeping turns, but nothing tight. Otherwise you put enough opposing forces through the driveline, sufficient to start breaking things.