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Pretty cool stuff. Nice picture.
Yeah I guess if it doesn't "home" back maybe there's a big spring in there to always force it homeward, so the control part only has to really push one way.
I'm very disappointed with myself for not checking the science after all this time. Unacceptable.
It's been very dry in NJ lately... there was one little thunderstorm the other day while I was driving home... the first opportunity I forgot to hit the stupid PSM OFF button, and then the next time I was on my block and there were some neighbors and kids around so I chickened out.
Now I'm going to California for a week so no more chances until then.
I'm surprised there aren't any youtube yahoos out there who've done this by now. Looks like I may miss my shot at being an internet sensation. Darn it.
Lastly, I may go for that switch idea after all. The dealer would never see it if I needed to go in for some reason, I could always undo it and things would be no worse than all the crimps under my carpet.
It would be a nice feature. I could route the wire to an area right under my seat. Then, technically (maybe /maybe not) I could even switch it while driving if I just shut off the ignition in neutral. Never tried this in the 955 but I think I could restart in my e38 BMWs while still moving in neutral... Or maybe I'm thinking of my 1978 Oldsmobile. I have a bad memory.
How much different is the turbo off the line compared to the S? If I put my S in manual or punch it to the floor so that it takes off in first I can break the tires loose. In a stoplight race, I make sure to turn off PSM otherwise traction control will kick in...even on hot dry pavement.
I assumed that taking off in 1st and giving it just half throttle would be enough to vaporize the rear tires.
I'm not sure but I also forgot to put it in 1st. I remembered 1st before, but that was when I had some regular gas in the tank (for the first time I swear).
Maybe someone else knows the specs more... I know I'm only 450 HP and I think the first ones in 2003 were a bit heavier.
You could try it but it would just consume more fuel and tires without any noticeable benefits. There really isn't any use for locked center differential at high speeds. High meaning anything over brisk jogging speed. I cannot think of any situation where a solid 50/50 split torque distribution would be a good thing if You aren't actually stuck or offroading.
But I agree that this is a thing that deserves further investigation. The hardware in drivetrain between Porsche Cayenne/Audi Q7/VW Touareg is 100% same. Yet basic torque distribution is different between these platforms. You can swap a transfer case from a Cayenne to a VW or from an Audi to a Cayenne and it will perform just like the receiver cars original would. The difference in behaviour is in the transfer case control module software. Now all we need is someone with a prommer and couple of hundred hours of spare time and couple of decades of experience and we can reverse engineer the control unit software. After that it's just writing a "100% to the rear at all times".bin and flashing it to the control unit
FWIW - IMHO it would be pretty solid to be able to lock the center and proceed at slow speed (below brisk jogging) AND faster. Many hill climbs (at any speed from jogging on up) don't require the low torque or throttle control of low range. It just makes it an easier go if all 4 tires try to go (and don't have to "wait" for PSM or other to kick in to help them along after they break loose and start spinning). And better downhill too, but for braking. Fully locked center, (and rear and fronts for that matter) are super handy, even without low engaged, in many situations.
As for the science, it occurs to me... any one of us could go out right now, unplug the motor or module, and become that youtube burnout star. Water makes it easer, but so do gravel, sand, neighbor's lawn, cardboard, wet concrete in a parking lot is particularly slick...
Transfer case stuck in low range- long lock works fine
[QUOTE=thesteve;18225336]So I just thought I'd share this since the other thread was pretty long and this interesting discovery (to me) is buried at the end.
I found out I can easily unplug the transfer case control module under the passenger's seat and have 2WD (and no clunks from my stretched chain). No errors, warnings or anything.
Then if I ever need or want AWD or 4WD, without even getting out of my seat, I can reach down there and plug it back in (after turning off the ignition) and have it all back in seconds.
I did this last night at a sold out Dave Matthews Band concert.
People in trucks and SUVs were driving over curbs and parking precariously perched upon grassy knolls at scary angles... I got excited since this has been my life-long dream as a 4x4-envying sedan owner.
So I put my hazards on, plugged it back up and found some parking.
Actually I ended up parking in the VIP section for free, but anyway it was a good test.
The reason my module is so easy to connect and disconnect is because I never properly extracted the original module, and have a newer spare I bought off eBay (that didn't solve the clunk issue) so I have more access.
Of course the right thing to do is R&R the transfer case, but I like this fix for now. Might even save on gas (?)
Any thoughts? Rotten tomatoes?
Cool idea to unplug transfer case module. I don’t think that would get it out of low range if stuck there though.
My ‘04 cayenne s got stuck in low range. Long lock still works and can be turned on and off. Trying for high range does nothing but console switch does appear to be working. I replaced the transfer case motor and the transfer case control module and neither made any difference. Eventually I removed motor and was able to manually turn the splined shaft with channel locks into the high range position. When I switch it back to low range it goes there no problem, but will not go back into high range. I took the motor off and again manually placed the splined shaft into the high range position. Vehicle drives normally with no error messages. When manually moving the splined shaft into high range it requires quite a bit of force to move it. It feels stuck, but if I try really hard it does shift. Moving the shaft the other direction (clockwise) is super easy with hardly any effort required. I’m thinking the servo motor just doesn’t have the torque required to turn the shaft counterclockwise. It used to work fine and I could hear it click right in. Not sure what changed in my transfer case to make this happen, but I did check the oil in it and it was a few inches below the fill port so a bit low. Wondering if there is any point in changing the transfer case oil in hopes that it could free up the shaft or should I go straight to replacing/rebuilding the transfer case…?!? Thanks.
As a test you could engage and disengage the high low modes with the motor unbolted from the transfer case.
Make sure it rotates back and forth at least. I wouldn't recommend using your fingers to test the torque...
Sorry I can't be of more help.
As a side point, I've been driving in rear-wheel-drive only mode since this post.
In that time I only plugged my module in once this winter when we had some significant snow.
Also, I routinely enjoy a slight fish tale as I merge onto US-1 after exiting my local car wash. Did it today.
As a test you could engage and disengage the high low modes with the motor unbolted from the transfer case.
Make sure it rotates back and forth at least. I wouldn't recommend using your fingers to test the torque...
Sorry I can't be of more help.
As a side point, I've been driving in rear-wheel-drive only mode since this post.
In that time I only plugged my module in once this winter when we had some significant snow.
Also, I routinely enjoy a slight fish tale as I merge onto US-1 after exiting my local car wash. Did it today.
Thanks for the test idea I need to still do that to make sure servo motor is actually attempting to make the shift to high range
I love the idea of this rear wheel drive only fishtail enabling simple unplugging mod hack
Game the Porsche system into giving us what we really want - full time rear wheel drive
If it gets sketchy, pull over and plug in the module
I don't mean to hijack your thread but I had to unplug the transfer case control module on my 2005 Turbo. When accelerating lightly from a stop going straight I was getting a wobbly wheel feeling from the right rear along with a few popping sounds. Then at around 40-50mph there's a vibration that feels like it will rattle the truck apart. This was followed by the occasional bang/slam sound. The vibration only stopped when the brakes were lightly applied and would resume again when accelerating.
All of that went away when I unplugged the module. Never got any codes or errors for it. The truck drives perfectly now.
LoBurnham, the only thing that sounds familiar is the clunking. In my case not really bad enough to call it a bang or slam... almost though at it's worst I guess.
I guess I try not to think about gas mileage. Right now wouldn't be a good time to do a test since I have to replace my left side pre-cat oxygen sensor.
Good question though.
Good thread and thanks to all. Have no issues yet but I offroad enough I'm bound to break something eventually. This is good info to have in my limp in home playbook.
Cheers, Mike
First: to test that it is truly in 2WD, you shouldn't even need to drive it. try jacking one corner of the front off the ground and see if you can turn that wheel. if truly in 2WD you should be able to turn a single front wheel as the front diff will allow it to rotate and should spin the front drive shaft which in your theory should be uncoupled from the rear drive.
my guess is that there is some static preload on the clutch pack which defines the initial bias ratio for the F/R drive split, so even with the computer disconnected you will get some limited drive to the front, but that is of course just a guess as I haven't torn one of these T-cases down to know what is really in there.
Second: There seems to be u HUGE misconception that a locked center diff will provide a 50/50 TORQUE split. this is completely false. A locked center diff will only provide a matched front to rear shaft RPM. if you have 0 traction on the rear axle the front will see 100 of the torque or vice versa.
An open center diff is what will actually give you an even torque split between the front and rear drive (limited by the maximum torque capacity of the lower traction axle).
07-08-2022, 06:12 PM
