[goose1]

Hi, guys. I've been searching for this answer for a couple of days now and hope you can help. I've been wondering why it is that Jeep still makes a PT4WD system. It would seem to me (and this is where I'm counting on your expertise and opinions) that FT4WD would be better all around. Is there some reason as to why PT is better-both on and off road? And what is the downfall of a FT system?

Thanks in advance...

BTW, Mods, If this is in the wrong area, please feel free to move it

[Sporer65]

With a part-time case, you have less wear and tear on the the front end. It is also cheaper since you don't have to worry about the front spinning at a different speed then the rear.

[Jerry Bransford]

A part-time 4x4 system is far more aggressive since it mechanically locks the front and rear axles together. It can only be used in off-road/very low traction situations.

A full-time 4x4 system is much less aggressive in that it allows the front and rear axles to turn at different RPMs and "slip" against each other in the right situations. This type of system is for paved road use and is not all that helpful offroad.

Read the two FAQs I wrote at the top of our General Offroad & Offroad Equipment forum that explains 4x4, lockers, etc.

[Bigbob]

I had a full time 4X4 in my '75 Dodge 1/2ton Powerwagon. It used a NP 203 transfer case. Off road it was great , had the same gear ratio as the NP 205 part time case. And although there may be some Full time cases today that don't lock up, the 203 indeed locked the front and rear together. The disadvantage to a full time case is you can't run a LSD in the front cause the front shaft has power going to it all the time and the steering would be goofy on the road. You also have all that mass turning all the time which really does not matter much. The CV joint on my '75 Dodge was going out all the time. And the biggest complaint wit fulltime 4X4 is, unless you have a 800 HP blown Hemi in it doing burnouts is real hard. Bob

[ovrszd]

Originally Posted by Bigbob

I had a full time 4X4 in my '75 Dodge 1/2ton Powerwagon. It used a NP 203 transfer case. Off road it was great , had the same gear ratio as the NP 205 part time case. And although there may be some Full time cases today that don't lock up, the 203 indeed locked the front and rear together. The disadvantage to a full time case is you can't run a LSD in the front cause the front shaft has power going to it all the time and the steering would be goofy on the road. You also have all that mass turning all the time which really does not matter much. The CV joint on my '75 Dodge was going out all the time. And the biggest complaint wit fulltime 4X4 is, unless you have a 800 HP blown Hemi in it doing burnouts is real hard. Bob

And for some of us kids, that last part is what sucks about FT the most!!!

[Bigbob]

Originally Posted by goose1

Hi, guys. I've been searching for this answer for a couple of days now and hope you can help. I've been wondering why it is that Jeep still makes a PT4WD system. It would seem to me (and this is where I'm counting on your expertise and opinions) that FT4WD would be better all around. Is there some reason as to why PT is better-both on and off road? And what is the downfall of a FT system?

Thanks in advance...

BTW, Mods, If this is in the wrong area, please feel free to move it

In all actuality there is no advantage to a part time today as most all, if not all, factory vehicles come sans locking hubs up front anyway. So the entire drive train is always spinning away. I had locking hubs in my CJ and I never did mind getting out and locking them. The full time is better in mild sand and mud being you will have power to the front and rear. But just a click of the lever gets you the same with part time.

[Jerry Bransford]

Originally Posted by Bigbob

In all actuality there is no advantage to a part time today as most all, if not all, factory vehicles come sans locking hubs up front anyway. So the entire drive train is always spinning away.

It doesn't sound like you really understand the differences between a full-time and part-time 4x4 system. If you tried taking a full-time 4x4 system... even if it had an uber-low ratio... through a tough trail, you'd see why no one would bother with a full-time system.

Even when you shift the full-time Quadratrac system into 4Lo (though not all Quadratracs have 4Lo), it has been shifted into a part-time mode. In the TJ's case, even though the front driveshaft does always spin in the absense of aftermarket manual hubs, it is still disconnected inside the t-case.

[Bigbob]

Originally Posted by Jerry Bransford

A part-time 4x4 system is far more aggressive since it mechanically locks the front and rear axles together. It can only be used in off-road/very low traction situations.

If memory serves me the TJ system is part time and a lot of guys drive them on the street! LOL I know what you meant.

Originally Posted by Jerry Bransford

A full-time 4x4 system is much less aggressive in that it allows the front and rear axles to turn at different RPMs and "slip" against each other in the right situations. This type of system is for paved road use and is not all that helpful offroad.

Correct, up till you lock the differential in the transfer case then there is no difference between a full time and part time in 4X4 mode. I do understand some vehicles don't have the transfer case lock feature. My NP 203 did. I think everything equipped with the 203 had high and low lock.

Originally Posted by Jerry Bransford

It doesn't sound like you really understand the differences between a full-time and part-time 4x4 system. If you tried taking a full-time 4x4 system... even if it had an uber-low ratio... through a tough trail, you'd see why no one would bother with a full-time system.

That would depend on the full time system. Like I said, 4WD low range or 4WD high range on a NP 203 is no different that on a NP 205. But, I would have rather had the 205 as it was a much better built unit. I never did have trouble with the 203 in 160,000 miles though.



Jerry, I've had both. I do understand how they work. My NP 203 definitely locked up in 4 high and 4 low range so off roading with it was no difference than having a NP 205 which was the standard for part time cases back then. A full time 4X4 system is basically a differential inside the transfer case which transmits power to both front and rear axles. The selectable locking mechanism in there makes it work just like it's part time counterpart when in 4LOW or 4 HIGH. I think the OP was referring to which is better. If the FT 4X4 system has a locking transfer case then as far as off road capability goes they would be the same. Of course I am considering they both have the same gear ratios and such. If you had FT on the street and wanted to have a locker "LSD" type differential up front you would have a Jeep that could be a little hard to handle. Selectable lockers would be the only option available to you. With a P/T 4X4 system any lockers are O-K on the street when 2WD is selected as the front axle is discoed from the transfer case. Now if you have a Wrangler type Jeep with a non-locking FT case you need to sell it to the highest bidder. I would not put Jeep past selling something like this soon.

[Jerry Bransford]

Originally Posted by Bigbob

Correct, up till you lock the differential in the transfer case then there is no difference between a full time and part time in 4X4 mode.

Once you lock up the t-case, it is no longer in full-time mode... locking it in 4Lo places it in a part-time mode. It is no longer in its full-time mode once you have locked it into 4Lo, it's now in a part-time mode. Full-time allows differentiation between the front and rear axles, part-time mode does not. Anytime you lock a Jeep t-case into 4-low, that is a part-time mode, regardless of what it is in 2wd or 4Hi.

[Bigbob]

Originally Posted by Jerry Bransford

Once you lock up the t-case, it is no longer in full-time mode... locking it in 4Lo places it in a part-time mode. It is no longer in its full-time mode once you have locked it into 4Lo, it's now in a part-time mode. Full-time allows differentiation between the front and rear axles, part-time mode does not. Anytime you lock a Jeep t-case into 4-low, that is a part-time mode, regardless of what it is in 2wd or 4Hi.

Ya lost me there.

Like I said before, the OP was looking at pros and cons of a full time system. The only difference will be on the hiway, all other factors being equal such as gear ratios. But I guess if you want to look at the full time being inferior while it's in full time mode, I think to be fair you'd need to test it against another equal rig in 2WD high range. Nobody is gonna rock crawl a full time rig unless he first goes into 4Low which will be locked, same as a part time rig.

[jeepdaddy2000]

Unlocked full time T cases use a differential or a viscus coupler to allow differentiation between the front and rear drive lines. The problem Jerry is trying to state is that many modern full time T cases do not have a lock mode. This means that you cannot lock the two drive lines together in low or no traction situations. These units work well on pavement in snow and ice conditions. They do poorly in mud and situations where only one axle has traction.

[Bigbob]

I have no argument with anyone. I merely tried to answer the OP's question. He did no specify which Full Time case. I based my answer on my personal experence with a Full Time system which happened to be in a 1975 vehicle.