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Use of Full Time 4 Wheel Drive
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Author:  Renegade03 [ Tue May 01, 2007 9:21 am ]
Post subject:  Use of Full Time 4 Wheel Drive
My brother-in-law is a Jeep Brand Manager. He insists that I should engage full time 4-wheel drive and leave it engaged 365 days a year for as long as I own my Liberty. This doesn't make sense to me. He says that there is no additional wear and tear, no additional load on the vehicle and no reduction in fuel economy. My position is that if that were the case, why have a transfer case at all. Simply make it an full time all wheel drive vehicle, as is available with the Grand Cherokee. I do understand that part time 4-wheel drive may be disireable during off-road driving, but he insists there is no good reason to operate a 4-wheel drive capable Liberty in 2-wheel drive. I use full time 4-wheel drive in the winter (in which case I do leave it engaged even if the roads are dry) and when the roads are wet but temperatures are above freezing. I haven't noticed a reduction in fuel economy during full time use (except that my fuel economy drops about 10 to 12% when ambient air temperature falls below 40 degrees F), but it seems to me that the components will wear more with constant use. What do you think? What do you do?
Author:  Dje Ryu [ Tue May 01, 2007 9:23 am ]
Post subject: 
My mileage definitely drops when I go to 4HI
Author:  hyedipin [ Tue May 01, 2007 9:26 am ]
Post subject: 
I am like your brother in law. Believe it or not, some people do prefer 2WD, because it is lighter on the steering wheel, less noisier (in my case) and sloppy. :) I drive in 4x4 Full Time almost all the time now, I like to know that I won't slip and throw my booty when I make that sharp turn fast before that car makes it here and I get stuck there..

One last reason they leave 2WD there on Selec Trac, the backlash, or drive train slack, or the lag, or the gap, whatever you would like to call it. I call it the BANG! On 4x4 FT you have the outrageous t-case bang on slow speed, stop and go traffic.. So that' sanother reason they like to keep the 2WD there.. Quadra Trac and Selec Trac are two different things, and don't even get me started on the Loredos so called "4x4".. it is just Honda AWD...... that's not even selectable, with no 4LO!

Dje Ryu wrote:
My mileage definitely drops when I go to 4HI


Not in my case, since I cannot get any worse than this is.. So if your mileage already sucks, it won't be any worse (15mpg in my case) I have seen NO difference. Matter of fact someone even had the discussion that 4x4 FT can even help the mileage because less drag by front wheels.

4HI might cause lower mileage, because it locks all four wheels and causes strain and the need for extra power to turn wheels on turns, etc.
4X4 FT works so much better since there is nothing locking (sort of).
Author:  Renegade03 [ Tue May 01, 2007 9:31 am ]
Post subject:  4 X 4 Lash
I agree. When in full time 4-wheel drive, there is a tremedous driveline lash (Bang in your terminology). I feel it when I engage reverse or drive, and I feel a bump when the vehicle approaches 40 mph, which I assumed was the torque converter locking and again as it downshifts as I am coming to a stop.

Obviously a Jeep Manager should know more about this than I do, but it just makes no sense to be in 4-wheel drive all the time, except for the improved traction.
Author:  hyedipin [ Tue May 01, 2007 9:33 am ]
Post subject:  Re: 4 X 4 Lash
Renegade03 wrote:

Obviously a Jeep Manager should know more about this than I do,.


I have heard some wild stuff from some jeep managers and "writers".. so don't be surprised to hear something that makes no sense..

Otherwise if the bang doesn't bother you, drive in 4x4 see how feels to go back to 2WD after a while :D You'll know what I mean.
Author:  Jeepjeepster [ Tue May 01, 2007 9:34 am ]
Post subject: 
If you want 4wheel drive, you must have a transfer case.

It does cause more wear on the front driveshaft and cv joints.

If needed, I would only use fulltime when raining. Ive yet to find a use on dry pavement.. Other than my tires sucking and spinning on dry blacktop. :twisted:
Author:  hyedipin [ Tue May 01, 2007 9:41 am ]
Post subject: 
Jeepjeepster wrote:
If you want 4wheel drive, you must have a transfer case.

It does cause more wear on the front driveshaft and cv joints.

If needed, I would only use fulltime when raining. Ive yet to find a use on dry pavement.. Other than my tires sucking and spinning on dry blacktop. :twisted:


Is it because you have locker?

I just like to know that when I need to suddenly accelerate, I won't be spinning senseless on some loose surface or on some road dirt..
Author:  Jeepjeepster [ Tue May 01, 2007 10:03 am ]
Post subject: 
hyedipin wrote:
Is it because you have locker?

I just like to know that when I need to suddenly accelerate, I won't be spinning senseless on some loose surface or on some road dirt..


yea, when you are turning, the locker puts power to the inside wheel and with the HP's, they just spin when pulling out and turning. Its even worse on wet black top.. Fulltime seems to help ALOT. :)
Author:  sleeve84028 [ Tue May 01, 2007 10:38 am ]
Post subject: 
You will see a drop in MPG between Full-Time and 2WD on dry pavement. The reason being is that some engery is lost at the front wheels when they are powered from heat and friction. That lost energy worked out to be ~0.5MPG change in my overall mileage when driving in Full-Time over a 2 month summer span.

For me and probably a lot of others:

2WD - Dry roads
Full Time - Rain / Snow or incliment weather
4Hi - when needed
Author:  hyedipin [ Tue May 01, 2007 10:39 am ]
Post subject: 
You will probably see that decrease in MPG if you were getting like 20mpg overall.. I have never been above 15.5 so.. :cry:
Author:  sleeve84028 [ Tue May 01, 2007 10:42 am ]
Post subject: 
Before trying the Full-Time exercise:

All types of driving (snow/wet/dry) in various drive modes = 15.7MPG overall

Leaving the Full-Time on = 15.1MPG
Author:  BVCRD [ Tue May 01, 2007 10:45 am ]
Post subject: 
When it is bad up here and my wife engages the FT 4x4, she typically loses about 2-3 mpg.
Author:  chetos [ Tue May 01, 2007 10:54 am ]
Post subject: 
hyedipin wrote:
You will probably see that decrease in MPG if you were getting like 20mpg overall.. I have never been above 15.5 so.. :cry:


I am glad I am not the only one. We went on a trip to Wy in January and saw 19 mpg. I was doing cart flips. my EVIC is always around 15.2.

Then again, I knew mpg wouldn't be the greatest when I bought my KJ. I just wanted a great 4wd system. My step dad swears by Jeep 4wd's. In fact his good buddy is a shop manager at Chevy dealer and he has a wrangler and will never get rid of it because "No other car company makes a 4x4 like Jeep."
Author:  jcphoto20 [ Tue May 01, 2007 1:42 pm ]
Post subject: 
arent you supposed to keep it under 55 when you have it in 4x4? i have a hard time believing the people that leave it in fulltime keep it under that all the time.
Author:  Guest [ Tue May 01, 2007 1:46 pm ]
Post subject: 
I know nothing of this drive train lash, or a bang! There is a bit of a howl with FT engaged, and steering is different, but I think it is better in FT4WD, In my opinion the steering "slop" is in 2wd mode. As far as fuel economy, it will remain about the same. I continue to get about 0.5 MPG BETTER in FT4WD than in 2WD, but that is negligible... over a full tank of gas that is less than 10 miles. I wouldn't make MPG a concern.

The selec-trac T-case is a NP-242, formerly known as a NV-242, & was installed on H1 Hummers as well. In the H1, there is no 2WD mode, only FT, PT & LO. So Your t-case is is fine in Full time, well, FULL TIME!
Author:  Dje Ryu [ Tue May 01, 2007 2:36 pm ]
Post subject: 
chetos wrote:
We went on a trip to Wy in January and saw 19 mpg. I was doing cart flips. my EVIC is always around 15.2.


You came here in January? Wow! Most people get scared when you mention Wyoming and winter months in the same sentence. :lol:
Author:  chetos [ Tue May 01, 2007 2:45 pm ]
Post subject: 
Dje Ryu wrote:
chetos wrote:
We went on a trip to Wy in January and saw 19 mpg. I was doing cart flips. my EVIC is always around 15.2.


You came here in January? Wow! Most people get scared when you mention Wyoming and winter months in the same sentence. :lol:


Yep, I am used to that!! We even went over the Big Horn Mtns via Ten Sleep-Buffalo, which was actually pretty easy because there was really very little snow for the time of year.
Author:  Dje Ryu [ Tue May 01, 2007 9:30 pm ]
Post subject: 
I bet it was still cold and windy, though.

It's actually been kind of strange, weather-wise, for a couple years. We've been getting a LOT of rain this spring, for instance. And lightning, like I haven't seen since I was a kid, today. Kinda shocked I can even post this, actually. ::knocking on wood the power doesn't go out::
Author:  snowsport [ Tue May 01, 2007 9:33 pm ]
Post subject: 
jcphoto20 wrote:
arent you supposed to keep it under 55 when you have it in 4x4? i have a hard time believing the people that leave it in fulltime keep it under that all the time.


Nope, just don't shift into or out of FT 4x4 over 55. I've had my KJ at highway speeds (65 mph +) many times in FT 4x4, and when passing other vehicles, up to 80-ish.

I'm not sure what the banging is about, that's not happening with mine. As far as whether I get better gas mileage, my theory is this: in full time or part time, my Jeep gets 1.6 kilometers to the mile, every mile..... :)
Author:  Dje Ryu [ Tue May 01, 2007 10:08 pm ]
Post subject: 
snowsport wrote:
1.6 kilometers to the mile, every mile..... :)


lmao. Nice!
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