| From | Message |
MACE
Dodge Dakota
JOIN HERE
3/20/2002
12:00:19
|
 Subject: Full Time 4x4 Transfer Case Qs?
IP: Logged
Message:
I've read through alot of archieved posts re:
the NV244HD 4WD Full Time/Part Time TC and still don't get a warm fuzzy re:
Center Differential: Planetary with lock Torque Split, F/R 48/52
Does this mean we get a full time torque split of Front: 48/Rear 52% or we have the capabilty in certain condtions to have this torque split?
Bottom line, on dry pavement with goobs of traction, is there still a full time F/R torque split or is only one specific wheel being driven, and if so, which wheel?
Now to muddy the waters, with LSD, are both rear wheels always having torque being applied, or only the right rear, and when it slips, LSD send torque to the left rear wheel?
And with LSD and F/T FWD, if both rear wheel are always being driven, what happens with the front wheels on dry pavement?
D/C nor New Venture can't seem to answer the above questions.
Thanks.
|
J. C. Brandon
Dodge Dakota
JOIN HERE
3/20/2002
17:05:45
| RE: Full Time 4x4 Transfer Case Qs?
IP: Logged
Message:
I've got the full time transfer case and I think it's fantastic.
Here's my stab at answering your questions; I'm sure others will have something to say as well.
With open diffs in front, center, and rear the truck splits the torque approximately equally to all four wheels as long as all have approximately equal traction and you are driving in a straight line. When you turn, the diffs allow each wheel to turn at a different speed (each wheel describes a different arc through a curve). As long as you still have approximately equal traction at each corner, each wheel will still be getting about the same amount of torque.
So that mostly describes driving on dry pavement. Here's what happens when things get slippery:
Let's say you are sitting on a level sheet of ice. All four wheels still have approximately equal traction but the total amount of traction available is greatly reduced. If you have good tires, a lightly loaded truck, a gentle foot and, a little bit of grip on the ice you might be able to drive out without spinning a tire. But if the total amount of traction available to all four tires adds up to less than that required to move the truck the tires will spin and you will go nowhere.
The configuration of your truck will determine which wheels spin:
If you have three open diffs the available torque will go to the single wheel with the least traction and it will spin.
If you lock the center diff the truck will split the available torque between the front and rear axles. Each axle will send approximately half the total available torque to its wheel with the least traction and you'll spin one front and one rear wheel.
If you have a locked center diff and rear limited slip the rear axle will try to turn both rear wheels until one of them breaks loose. Then it will send all its available torque to that wheel and you will spin one front and one rear.
That's what happens when there is not enough total available traction to move the truck.
Locking and limited slip diffs help you when there is poor traction but still enough total to move the truck. They split the available torque up to try to match it with the available traction. If you lock the center diff the torque gets split about evenly front to rear. If that is enough to move the truck without spinning a wheel you can drive out. If not, you spin two wheels and get stuck.
If you lock the center diff and have rear limited slip, the available torque gets sent to three wheels. If the total traction available at those three wheels is enough to move the truck you drive out.
None of this means the torque is always sent to a particular wheel. Torque goes to each wheel in about the same amount until any wheel begins to slip. That's when you need locking or limited-slip diffs.
It's complicated and easy to misunderstand. But if you learn it you can drive past the guys who don't bother to understand it. You can even pull their trucks out of the mud.
-J.
|
JP
Dodge Dakota
JOIN HERE
3/20/2002
23:10:23
| RE: Full Time 4x4 Transfer Case Qs?
IP: Logged
Message:
I think you have it right J. I have tried to explain it a couple of times without evident success. I think I will copy this and save it to a file. As far as torque splitting is concerned I thought that was usually done in systems with fluid couplings.
JP '01 4.7 SLT+ CC AWD LSD
|
MACE
Dodge Dakota
JOIN HERE
3/21/2002
11:17:40
| RE: Full Time 4x4 Transfer Case Qs?
IP: Logged
Message:
Well, let me say this is a more detailed and technical explanation than what I got from DC...New Venture Gear just totally blew me off.
You answered my main concern re: torque split when on dry pavement, as well as my LSD question...thanks!
|
J. C. Brandon
Dodge Dakota
JOIN HERE
3/22/2002
00:04:11
| RE: Full Time 4x4 Transfer Case Qs?
IP: Logged
Message:
Glad I could help. Four-wheel drive systems can be confusing, mainly because the manufacturers use too much marketing language and not enough explanatory language. This is further compounded by owners who believe the marketing hype and embellish it with their own noise.
Just remember that at any given moment your truck is putting out a fixed amount of torque and your tires are finding a fixed amount of traction. If torque increases or traction decreases so that they are greatly different, you get stuck. The only question is which tire or tires digs you in. Open diffs send all the torque to a single contact patch which very quickly gets overwhelmed. Limited-slip or locking diffs split that same amount of torque to two, three, or four contact patches which increases the applied traction by a factor of two, three, or four. And you drive merrily on.
I once unstuck a very heavy load (a 40,000-pound tractor trailer rig) with my Dakota. After yanking the semi, I looked at the road surface and saw four shallow holes where each of my tires had dug in. The surface was level, compacted dirt and gravel. I dug four holes because the tires all had equal traction available to them. Although the tires spun, they did find some traction and the total traction available was enough to pull the stuck truck. With less traction -- say from smaller tires or higher tire pressure, I would not have been successful. With more torque -- say from a heavier throttle foot, I would not have been successful.
Like I said, it's worth learning this stuff.
-J.
|
MACE
Dodge Dakota
JOIN HERE
3/22/2002
11:57:25
| RE: Full Time 4x4 Transfer Case Qs?
IP: Logged
Message:
I agree, one needs to know both the capability and limitation of their vehicles traction ability.
For the past 10 years I've owned either 4x4s (Tracker and Jeep) or AWD (2 Subarus) and now the DAK with the Full Time/Part Time TC.
I needed to get comfortable with the knowledge of what my DAK can do in certain conditions.
With my 4x4s, I learned it was better to be in 4HI instead of RWD, and not get stuck, shift to 4WD, and try to get unstuck.
As for AWD and the Subarus, they don't mix too well on beaches (tough lesson learned on a young AWD driver)
Thanks again.
|
DodgedogJB
Dodge Dakota
JOIN HERE
3/22/2002
20:44:06
|  RE: Full Time 4x4 Transfer Case Qs?
IP: Logged
Message:
All I need to know about my full time transfer case is that I go much further than those that don't have it without getting stuck! And when I do, reverse usually gets me out.
Mace--->Can you explain a little more on what you mean by "Subarus and beaches don't mix??" I used to drive an AWD car on the beach everyday and never ever got stuck. And it wasn't because I was going fast! Unless you mean beach=saltwater=premature failure? I'm confused either way.
Joel
|
MACE
Dodge Dakota
JOIN HERE
3/26/2002
09:06:41
| RE: Full Time 4x4 Transfer Case Qs?
IP: Logged
Message:
DodgedogJB:
I'm not exactly sure of the location/name of this beach, it was in Rhode Island near Kingston, where they have sandy 'roads' you can drive on to reach the beach...driving my 96 Outback close to the water line on hard wet sand was no problem, it was when I came to the end of the beach and a rock jetty, and I had to turn around, we got stuck in dry loose sand, the car and wheels just sunk down in the stuff...again, a rookie mistake, but never repeated.
Where did you drive your Subaru on the beach?
|
DodgedogJB
Dodge Dakota
JOIN HERE
3/26/2002
18:01:21
| RE: Full Time 4x4 Transfer Case Qs?
IP: Logged
Message:
Mace-->
I didn't have a Subaru I had an Eagle Talon Turbo AWD. I lived on the Washington Coast where it is legal to drive on most of the beaches. I drove in wet and dry, loose, deep, rutted sand on a weekly basis and never once even got close to getting stuck. Not sure what the difference in the AWD systems were between the cars but I took that car all over the beach without fail. It was actually quite funny to do it on the weekend because most of the locals that cruise the beach in their four-wheel drives didn't recognize me for the first months I had the car and they followed me so the could pull me out for $20 when I got stuck. Thing was, they would end up stuck because they wouldn't have it in four-wheel drive and would have to get out and lock their hubs. I would of course do some donuts around them throwing sand all over the place until they recognised me. The only part I hated about driving on the beach was the hose down procedure afterwards to get the salt and sand off. I guess its just one of the things you do when your 18. Now I drive my Dakota and make $20 per tourist.
Joel
|
MACE
Dodge Dakota
JOIN HERE
3/29/2002
15:55:30
| RE: Full Time 4x4 Transfer Case Qs?
IP: Logged
Message:
Thats pretty cool Joe.
We've contributed funds to a few 4x4 owners in Pebble Beach, Montauk, and of course, RI.
Agree, much exterior and underbody washing needed after beach driving, also pay much attention to getting all the sand out from the brakes/wheels and exhaust.
|
Paul
Dodge Dakota
JOIN HERE
12/12/2003
00:07:03
| RE: Full Time 4x4 Transfer Case Qs?
IP: Logged
Message:
I am about to order a new Dakota, I want to make sure i get the right transfer case. Does the AWD transfer case also have 4hi and 4low or is it just AWD, I do allot of hunting in the Bavarian Alps and climb huge hills and use 4wd all the time on my truck now. I am switching from Ford to Dodge for the larger truck, more room for my hunting dogs and hunting friends on the inside. However I have not been able to pin down what transfer case is the best. what about MPG vs the two transfer cases. I dont have the abiltiy to go to a dodge dealer and ask questions, as i am stationed in Germany and must buy through the local PX.. Help me out here..
Thanks in advance
Paul
|
paul
Dodge Dakota
JOIN HERE
12/12/2003
00:12:26
| RE: Full Time 4x4 Transfer Case Qs?
IP: Logged
Message:
One more quick question. Does anyone know the top speed of the 04 Dakota with the v-8 Like i said above, I live in germany and drive allot on the AutoBahn. My current ford has a limiter set to 90mph(way to slow for long autobahn trips). How fast can you go before you hit the limiter on the Dakota??
Thanks.
|
Scott
Dodge Dakota
JOIN HERE
12/12/2003
07:57:29
| RE: Full Time 4x4 Transfer Case Qs?
IP: Logged
Message:
My `02 has the full time transfer case and it has hi , lo , neutral , and AWD selections.
Not sure on the top speed , but I`ve had mine to a little over 100 and it was still going.
Hope this helps.
|
MONDTSTER
Dodge Dakota
JOIN HERE
12/14/2003
19:52:55
| RE: Full Time 4x4 Transfer Case Qs?
IP: Logged
Message:
My $.02 on AWD/Full time transfer cases.
Everything that has been said about the AWD transfer cases is pretty accurate. I am just going to add my own experiences with the AWD/Full time transfercases.
I used to be very heavily into import drag racing and have owned several Mutsu/Eagle AWD talons/eclipses. They were very good, fun cars even to drive in the winter due to the AWD, but even with them having rear LSD in them did not help when a rear tire was lifted off the ground. The car would still not move, and all power was being sent to that wheel. From my experiences, even if you have LSD in the front or rear I don't feel it makes much difference with an AWD transfercase. Now, MAYBE my LSD's were bad or broken, but I don't think so because every one of the cars that I had did it.
On another occasion, we were at a friend's private lake where we had been drinking for a long time that night. We decided to take his quadratrac (AWD) equipped Grand Cherokee out onto the beach which had very loose sand and we didn't realize it. This Jeep had open diffs, and we promptly buried the jeep in the sand until it sat on the frame rails. With all four wheels off the ground, the power was being transferred equally and spinning one front wheel and one rear wheel like it should. But in order to get it unstuck we had to put cement blocks under all 4 tires or else the power would have been transferred to the other two wheels that didn't have traction.
Another time a friend of mine had a chevy blazer that had a NP203 transfer case in it and he installed a set of lockouts on it. Of course since it was an AWD transfer case, the truck wouldn't even move with the hubs free because all the power was being transferred to the front wheels.
In my opinion, full time four wheel drive sucks unless you are going to stay on the road. If that is the goal, then it is a great feature over normal 4 wheel drive because you won't have the jerking and binding of going around tight corners with it and it is very predictable in the snow for fun, agressive driving. People just need to understand the limits of AWD and the fact that it isn't true 4wheel drive.
On another note, the manufacturers could make a prettty good off roader out of a full time 4x4 truck if it was equipped with 4 wheel ABS. If the ABS module was programmed correctly it could monitor all 4 wheels and if it sensed that wheels were slipping while others were moving slower or are stationary it could apply the brakes on the wheels that were spinning. That would be kind of cool.
|
| | P 1 |
|
Post a reply to this message:
Username Registration: Optional
All visitors are allowed to post messages
|
