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PT/FT 4WD
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=1&t=17706		 Page 1 of 2
Author:  Joe Jeep Owner [ Thu Feb 15, 2007 11:38 am ]
Post subject:  PT/FT 4WD
Ok I'm getting old and my memory is going, with all this snow/ice and everything I need a refreshed:

PT 4WD - Wet, icy and snowy roads at low speeds (not sure what speed), not on dry roads

FT 4WD - Wet, icey and snowy roads at higher speeds (highway and below), offroading and mud.

4WD Lo - Towing and wheeling, both at slow speeds.

I always forget what to use when it snows/ices over, for deep stuff on backroads and highway I use FT, so clearer roads with ice patches I use PT.
Author:  Jeger [ Thu Feb 15, 2007 11:56 am ]
Post subject:  Re: PT/FT 4WD
I just edited your post to what is correct. changes are in bold

PT 4WD - Wet, icy and snowy roads at any speed (within reason) (not sure what speed), not on dry roads offroading and mud.

FT 4WD - Any road condtions, dry, wet, icey and snowy roads at higher speeds

4WD Lo - Towing i suppose if it was offroad and slow going and wheeling, both at slow speeds.


Full time can be used whenever you feel like it. Part time should not be used on dry roads... The lights help a lot Full time is green...go ahead, no worries. Part time is yellow....caution drive train could bind on dry roads.
Author:  unixxx [ Thu Feb 15, 2007 12:04 pm ]
Post subject: 
Joe Jeep Owners, you want to use part-time (PT) 4WD for mudding/backroads, full-time (FT) 4WD/2WD for towing, and full-time (FT) 4WD for clearer roads with ice patches. Full-time 4WD can be used on pavement because it has a differential in the transfer case. Part-time 4WD Lo and 4WD Hi can't be used on pavement because they lock the axles together in the transfer case. The top speed of part-time 4WD is something like 40mph. Essentially, youll want to use part-time for off-road, full-time for on-road where you need traction, and full-time 2WD for everything else.
Author:  wendell [ Thu Feb 15, 2007 12:22 pm ]
Post subject: 
Part time 4wd can be used up to 55 mph, however, if road conditions are such that you need 4wd, I dout that you will want to be going 55. People have been posting that you don't need 4wd unless there is 6" of snow on the road, I don't buy that. This last blizard has left a thin sheet of hard pac snow on the road, I you use 4-hi more for handling than traction in these conditions. You can also use 4wd on dry pavement as long as your not turning. I try to use my 4wd at least once a month to keep it operating properly. Here in northern Ohio, we have a lot of long straight roads, so I'll pop it in for a couple of miles. I use low range as well, but thats in the driveway or going back to the barn. A lot of time people will a used 4x4 and the 4wd was never used, and when they try to use it, it's stiff and hard to engage, or something breaks. So as a rule of thumb, I try to use both ranges at least once a month. I just play with it in the yard if nothing else. The 4wd engages alot smoother now than when it was new back in october. "O YEAH', the people posting about the 6" of snow aren't on this forum, we like to play with our 4x4's here, it only takes a sciff for us ha ha.
Author:  unixxx [ Thu Feb 15, 2007 12:35 pm ]
Post subject: 
Just make sure you don't use part-time on roads that aren't flat. As an example, when your front wheels go over a speed bump, they need to turn faster than the back wheels. Part-time won't let the front and rear wheels turn at different speeds.
Author:  Joe Jeep Owner [ Thu Feb 15, 2007 12:55 pm ]
Post subject: 
Thanks guys, like I said I always forget and sometimes it isnt clear on which one to use.

This morning I drove to work in PT 4WD, there was patchy ice on the road so I thought this would be better. Normally I would drive in FT 4WD in deep or packed snow but like I said I knew one of them was really bad to drive fast with and I couldnt remember.

I wondered for rain too, sometimes I like to use it to help with hydro planning and was thinking PT but again, with the speeds I wasnt sure. I pretty much just use FT for everything and wanted to start using them correctly.
Author:  sleeve84028 [ Thu Feb 15, 2007 1:31 pm ]
Post subject: 
My Take

Full Time in the rain, snow and on all surface streets [don't engauge / disengague over 55MPH & driving speeds are not limited)

Part Time in the dirt or off road [don't engauge / disengauge over 55MPH & I wouldn't be driving over 55 if I needed this]

4-low for rocks or situations that require a lot of crawling power... [never drive over 15MPH to be safe]


I use the Full Time setting the most because I don't have to worry about anything happening to the driveline.
When I venture off road or in particular situations where there is a lot of snow or ice, I'll put on the part time
I use 4-low to do hill climbs in the woods and go over "stuff"

I never tow with the 4WD turned on because I don't want to put that much strain on the T-case chain

Edit: Although, I admit I've used the 4-low to assist in some shrub removal from the front yard (it was an excuse to use the tow strap)
Author:  RespectMyLibertay [ Thu Feb 15, 2007 2:27 pm ]
Post subject: 
I love full-time 4-wheel drive 8)
Author:  rs4mtnitro [ Thu Feb 15, 2007 8:33 pm ]
Post subject: 
unixxx wrote:
Joe Jeep Owners, you want to use part-time (PT) 4WD for mudding/backroads, full-time (FT) 4WD/2WD for towing, and full-time (FT) 4WD for clearer roads with ice patches. Full-time 4WD can be used on pavement because it has a clutch in the transfer case. Part-time 4WD Lo and 4WD Hi can't be used on pavement because they lock the axles together in the transfer case. The top speed of part-time 4WD is something like 40mph. Essentially, youll want to use part-time for off-road, full-time for on-road where you need traction, and full-time 2WD for everything else.


It doesn't have a clutch it has a differential. And I am not sure if you are talking about part time in general or low range but part time high range does not have a speed limit other then when you engage it which I believe is under 55mph .
Author:  unixxx [ Thu Feb 15, 2007 10:46 pm ]
Post subject: 
My bad, I was thinking of the Grand Cherokee transfer case. Thanks.
Author:  chetos [ Fri Feb 16, 2007 10:53 am ]
Post subject: 
unixxx wrote:
Just make sure you don't use part-time on roads that aren't flat. As an example, when your front wheels go over a speed bump, they need to turn faster than the back wheels. Part-time won't let the front and rear wheels turn at different speeds.


Does this apply to wet/icy/snowy/muddy roads?
Author:  sleeve84028 [ Fri Feb 16, 2007 1:17 pm ]
Post subject: 
You don't want to use the Part time system when the road or ground surface won't allow for some wheel spin. On snow or mud you'd be fine because the friction between the tire and ground is reduced so much... But when the roads are only wet, or worse, dry the front tires can't slip like they need to avoid a driveline bind situation.
Author:  RespectMyLibertay [ Fri Feb 16, 2007 3:05 pm ]
Post subject: 
On trails where it's mostly rocks and gravel I wouldn't dare using part-time. That's why I love my full-time!
Author:  unixxx [ Fri Feb 16, 2007 4:15 pm ]
Post subject: 
Gravel should be fine because it's loose and allows the tires to slip. Rocks should also be fine because, unless they're perfectly flat, some of the tires will have less pressure on them and be able to slip. Part-time is bad on paved roads because we design roads to have the highest coefficient of friction possible and have such uniformity that all wheels have excellent traction.
Author:  RespectMyLibertay [ Fri Feb 16, 2007 5:02 pm ]
Post subject: 
The problem with the closest trail to me is that it's made of dirt with a gravel top that has very little give. Mixing that with the occasional cement "traction-block" platforms, flat rocks (practically little tables) incorperated into the road itself, and some turning convinced me to throw it into full-time. It is considered gravel, but it's just a few little stones on top of a bunch of huge ones and really hardened dirt. A of what's loose get's blown or washed of the trail. I tried to turn once and had some minor driveline binding. Since that seems to make the tires slip I got through the turn each time but it was noisy. Threw it into full-time, no problems. I think maybe I shouldn't have called it gravel. But when rock-crawling, I don't use part-time, I use 4-lo. I would think that 4-lo would have the same problems as part-time on the surfaces I described earlier, but it doesn't. Like you said, unixxx, when articulating and going on funny angles, not all tires have the same pressure and some are allowed to slip, which prevents driveline binding. I can imagine hearing that noise in 4-lo wouldn't be good :oops:
Author:  riptricket [ Fri Feb 16, 2007 5:29 pm ]
Post subject: 
so i was just making sure that here in oklahoma, we have been having a hellaof lotta ice and i drive down the high-way at 45-65 mph with the 4-part-time on. is this bad?
Author:  itsajeepthing [ Fri Feb 16, 2007 5:36 pm ]
Post subject: 
Generally I think people get too paranoid with the P/T 4wd thing. I've wheeled my ride pretty hard over miles and miles of rock. At crawling speeds, particularly in 4 low, there is enough torque to break a tire loose here and there as needed, even on really sharp turns, without destroying the driveline. You just hear the odd tire chirp. If you are steady and slow, and not bouncing your jeep or mashing the gas, binding is really not a concern in this scenario. If you are locked at the diffs and in PT 4wd, that's a different story.

Where binding can be a problem is when you turn on very tacky surfaces like pavement, at normal travelling speeds. At speed it takes no time at all for the slack in the drivetrain to completely wind-up and bind. When that happens, your are either going to break, or you will start to encounter fun stuff like wheel hopping. Even the FT 4wd systems can get wound up slightly when turning sharp on pavement - first sign is a heavy feel in the steering wheel.
Author:  BVCRD [ Fri Feb 16, 2007 5:36 pm ]
Post subject: 
riptricket wrote:
so i was just making sure that here in oklahoma, we have been having a hellaof lotta ice and i drive down the high-way at 45-65 mph with the 4-part-time on. is this bad?




The PT isn't bad on ice, but 65 mph could be. Wait, you guys don't have ditches down there. :D
Author:  WGNMANinaRENEGADE [ Fri Feb 16, 2007 5:40 pm ]
Post subject: 
HOW ABOUT THIS ONE? [IT'S HOW I EXPLAIN IT TO MY WIFE!]

if you THINK you're gonna slip, use FULL-TIME
if you KNOW you're gonna slip, use PART-TIME

OR

i can use FULL-TIME, ALL THE TIME, but I can only use PART-TIME, SAOME OF THE TIME.

then i tell her, you are a full time wife, if you wanna be part-time, drive somewhere else...
Author:  itsajeepthing [ Fri Feb 16, 2007 5:40 pm ]
Post subject: 
lol !! :D
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