Massive Porsche X-fer case failures

Status
Not open for further replies.
G

GKoenig

Joined
Jul 25, 2017
Messages
4
Location
Texas
I recently bought a new 2016 Porsche Cayenne V6. It developed a very bad off-idle hesitation at 11k miles, turns out it was the x-fer case slipping and the computer was trying to adjust for it. I quickly discovered that virtually every x-fer case built from 2008 has had reliability issues and the only TSB/fix so far was to install an extended case vent tube from the undercarriage to the engine bay. Supposedly this helps prevent water and dirt from getting into the case. Porsche seems to be very good about replacing the entire case without much trouble but it appears that it is either a poor design, materials, or lubrication, must likely all 3.
The design uses a wet clutch pack to vary the full-time AWD torque between front and back. BMW x-drive uses the same technology, however, they use sensors to monitor the oil and clutch pack wear and provide a warning when the oil needs to be changed.
Porsche recommends that the x-fer case oil be changed at 90k miles. Obviously this is a problem. Many owners have resorted to changing their own x-fer case oil between 5k-20k miles to be proactive. The results are shared online and the majority of the complaints are "burned oil" - that is, very dark color with a very "burnt smell".
The Porsche recommendation for the case oil is ESSO LT 71141(formerly Italian, now Mobil 1):
cSt @ 40º C 37.2
cSt @ 100ºC 7.4
Viscosity Index, ASTM D 2270 168
Density @15º C g/ml, ASTM D 4052 0.855
FP 219 deg. cel.

Many are sticking with the OEM oil and just changing it regularly. BMW oil is also ESSO LT71141 with a BMW OEM label.

I would like to find the best alternative oil to use as I believe there are much better oils now since the ESSO spec was adopted many years ago.

Since the clutch pack is "wet", the oil plays a critical role in its reliability, performance, and efficiency. The clutch is slipping by design which creates a tremendous amount of heat. Is the flash point of a viable ATF fluid a good indicator of a suitable replacement? If so, Amsoil looks to have a good product.
How about viscosity? Since the clutch is designed to slip, viscosity will heavily influence performance?

Regardless, the oil is being cooked by friction rather than contamination from moisture and dirt.

I have researched 12 different ATF oils and can not determine which specifications would suit this application. It is a transfer case, not a transmission and therefore will have completely different requirements for oil. Why would it not require something similar to a limited slip rear differential oil as it also has a slipping clutch design?

Perhaps we will require a cold weather oil and a hot weather oil?

Is there an additive that would help with the heat?

Thanks in advance!
 
Last edited:
That's a tough one.

The viscosity at 100C is very close to say a Mercon V.

I'd be tempted to try Valvoline MaxLife ATF or perhaps even royal purple synchromax (syncromax is manual trans fluid for applications that require ATF).

Another dedicated transfer case fluid is Motorcraft XL12.

I think the t-case would benefit from some extra friction modifiers to reduce friction and heat. Just my .02

Of course, use all these at your own risk, since they're "not approved."
 
Thanks for the response, and you bring up another point, oil manufacturers list "LT71141" compliance, not "Porsche" approved compliance.

My rig has 11k miles and the case was just replaced, as have thousands of others, I have no hope of keeping this P.O.S. over the long haul, but changing the oil is a snap, plus its less than a quart.
 
So it's a transfer case that works full time, and uses wet clutches to vary torque, but is running on basically automatic transmission fluid?

ATF in a transmission typically lasts a decent number of miles because it is cooled via the car's existing cooling system.

I would imagine that is not the situation for your transfer case, and I bet the actual fluid volume in there is low and that provides less of a buffer against heat.

Since you are still under warranty, I would stick with the mfr recommended fluids, but is there any way to improve the cooling for the transfer case?
 
Originally Posted By: GKoenig
Thanks for the response, and you bring up another point, oil manufacturers list "LT71141" compliance, not "Porsche" approved compliance.


It's pretty rare to see an 'approved' oil unless it's OE branded oil. Usually it's 'meets specifications of' or something to that effect.

I wonder what that repair bill would cost out of warranty.
 
I think they added a plastic air scoop to the bottom as well, I will look at this too, good tip.

I would think that I could get away with putting anything in there since there is a known issue and replacement is commonplace.

I plan to try a new oil and see how it effects performance, I may know within a few hundred miles if the viscosity is doable or not. If performance appears to be unchanged, I will drain it at 1k mile intervals to have a look. There has got to be a better oil than what they are using.

$5k roughly to have it done outside of warranty, they do not appear to be fixing the clutch but rather replacing the entire unit.

Porsche seems to be "blessing" Mobile 1 oils right now. Motul is popular with the small shops. They want $55 for a quart of OEM t-case oil at dealer.

So far, I am leaning towards Amsoil ATF as its viscosity is closest to ESSO with a much higher FP -> 235 vs. 219
 
Last edited:
What is so darn hard about building a reliable TCase? Yah, I know it is an antique, But the New Process 219 229 etc T Cases used a viscous coupling. In 20 yrs of GWags , no failures, and I broke just about everything else. Just curious, did this engineering marvel have a low range, like a real SUV?
 
Negative on the low range, this is soccer-mom performance brutha!
blush.gif
 
Originally Posted By: dparm
I'm hoping MolaKule can chime in here...




lol thats what im hoping for as well.
 
It's a design problem in minimal lubricant volume for cooling, hence providing minimal margin of safety as in thin vs thick debate.
 
I would use a Synthetic oil with the closest viscosity to the OE spec, Mobil1 or Amsoil.
Extra cooling is essential, like the air scoop.
Also, keep the wheels inflated equally and rotated very often. Of course, they have to be identical. 1/16" difference in diameter can add heat.

PS: The AWD that uses a vascous coupler (Borg Warner) is based on a different mechanism, no cluches inside that one. That's what the AWD Ford Explorer had in their V8.
PPS: For who asked about a Hi-Lo range changer. Those 4x4 TC are not AWD, an AWD is basically a true differential with some kind of limited slip. They stay engaged all the time.
 
Last edited:
Originally Posted By: SoNic67
I would use a Synthetic oil with the closest viscosity to the OE spec, Mobil1 or Amsoil.
Extra cooling is essential, like the air scoop.
Also, keep the wheels inflated equally and rotated very often. Of course, they have to be identical. 1/16" difference in diameter can add heat.

PS: The AWD that uses a vascous coupler (Borg Warner) is based on a different mechanism, no cluches inside that one. That's what the AWD Ford Explorer had in their V8.
PPS: For who asked about a Hi-Lo range changer. Those 4x4 TC are not AWD, an AWD is basically a true differential with some kind of limited slip. They stay engaged all the time.


There are exceptions to that rule in your PPS.
VW 4XMotion on the Touareg is a AWD car with a Borg Warner Transfer Case. It uses a Torsen center differential to provided the AWD capability.
The Toyota Landcruiser J100 has a similar type of system before the Touareg got it, AWD with transfer case.
 
Originally Posted By: zeng
It's a design problem [that highlights] minimal lubricant volume for cooling, hence providing minimal margin of safety...


I have to agree with zeng for once.

It sounds as if the TC design was carried out with minimal attention to heat rejection and proper friction characteristics. Too many designs for AWD TC's are coming out with minimal fluid volumes and no heat exchangers (cooling tanks).

There are two fluids I would recommend, in this viscosity range, that might be less susceptible to oxidation and heat degradation and they are:

http://www.amsoil.com/lit/databulletins/g1966.pdf

and

https://www.redlineoil.com/product.aspx?pid=51&pcid=9
 
Last edited:
Get a electric oil pump (They make these for ex. cooling differentials and manual trans in race cars. Essentially what we want to do.) Set it up to suck fluid from the t-case drain, and pump it through a filter head (use the largest filter you can make fit) up to the front of the car to a oil-to-air cooler then back to the tcase. Depending on the size of the cooler and filter, length of lines this will add 1-2qts of fluid to the system, along with filtration and cooling..
You could change super secret fluid every 3k miles and still smoke tcases; or drop the fluid temperature 80-100F, extend your fluid intervals to 15-20k, and simultaneously have it actually hold together long enough to talk about.
 
Last edited:
http://www.setrabusa.com/products/oilcontrol/pumps/index.html
http://www.setrabusa.com/products/oilcoolers/diff-gearbox/index.html
https://www.amazon.com/dp/B000CSEUSS/ref=psdc_15727081_t3_B000CSGT64
That filter head would accept from small 3614 filter up to a large PH8A filter, or possibly even larger as there is a part for an old tractor motor that is a long PH8A.
Also, since it has dual inlet/outlet, it would be trivial to add a temp sensor into one of the extra ports, showing you how hot the fluid is coming out of the tcase. 250F would be about the max you would want to see, and only intermittently. 180-200F long term would be optimal.
 
Status
Not open for further replies.

Similar threads

buck91
Ford F150 transfer case
Replies
1
Views
421
wlk
S
75W-90 Synthetic WITHOUT Limited Slip Additive - Mobil Delvac?
2
Replies
26
Views
2K
Spddm0n
X
2018 Rav 4 "Adventure" model transfer case/differential fluid confusion.
Replies
5
Views
283
XB_Fan
H
Transfer case & diff fluids
2
Replies
32
Views
3K
Jpc1623
Dude-Man
HPL ATF Green CC or Amsoil ATL?
Replies
12
Views
1K
Ray S
Back
Top