Difference between part time and full time 4X4

[K15004X4]

I was told by the previous owner that part time 4X4 is for off-road use and full time is intended for winter road driving. What exactly is the difference between the two? And are there any reliability issues with using the Full Time 4X4 on the road at highway speeds in the winter?

[fredjacksonsan]

Part time 4wd locks the transfer case so that the front and rear wheels turn at the same speed.

Full Time leaves the transfer case unlocked, so the front and rear can turn at different speeds.

It's important on the road, since there is no wheel slippage under normal conditions and if the t-case is locked you can break something if you're in Part time.

If you've got the Select Trac, where your transfer case is labeled:
2WD
4WD Part time
4WD Full time
Neutral
4 Lo


Then there's no issues with reliability leaving it in 4Full Time. You just might have a little less MPG.

[xj31]

Originally Posted by fredjacksonsan

Full time 4wd locks the transfer case so that the front and rear wheels turn at the same speed.

Part time leaves the transfer case unlocked, so the front and rear can turn at different speeds.

It's important on the road, since there is no wheel slippage under normal conditions and if the t-case is locked you can break something if you're in Part time.

If you've got the Select Trac, where your transfer case is labeled:
2WD
4WD Part time
4WD Full time
Neutral
4 Lo


Then there's no issues with reliability leaving it in 4Full Time. You just might have a little less MPG.

Check your first 2 sentences.The 3rd is right so I know you understand,I think you mis-typed

[fredjacksonsan]

Thanks; corrected. Isn't alcohol wonderful?

[xj31]

Happy New Year!!!

[hulkmn069]

i thought the part time was for on road stuff cause when it senses a slip then it'll kick in the front wheels instead of running them all the time and wearing down the mpg??? besides i'd want all four turning in the mud at all times to keep me from getting stuck and when on ice cause they get jumpy in part time on ice and snow and don't handle as well

[fredjacksonsan]

Full time = can leave on all the time (allows slippage)

Part time = part time use only. This is what you'll want in the mud.

[fawalley]

I know it's late replying to this but if I may add,

Hulkmn069 said " i'd want all four turning in the mud at all times"

Now in 4x4 part time you are locking the front and rear together but not all 4 wheels will spin together. You may get 1 front, left or right, and 1 rear, left or right, together. I order to have all 4 locked and spinning together you'd also have to installed some type of locking differential as well so you'd have 2 fronts, left and right and 2 rears, left and right.

Just don't run in on the pavement like that.

Thanks

Ta Ta

[msdz]

Full time 4WD is considered the "dummy" 4WD around here. Full time 4WD is the SAME as part-time 4WD only difference is no driver input is needed. No need to turn hubs in or out. No need to make a transfer case selection. If a vehicle is labelled as part time then what it usually means is the transfer case is disengaged OR the hubs and transfer case is disengaged OR driver has to disengage hubs manually and transfer case is disengaged which improves MPG. A transfer case is engaged or it isn't, if it is in between then you have problems and need to get it fixed. A transfer case does not allow one wheel to spin faster or slower then the others, that is all in the differentials. Lets say you have a TRUE 4WD and the diffs are "LOCKED" together, then you would not be able to turn to good and also cause a lot of strain on your inner axles possibly causing them to break. Even the Detroit lockers you can buy and have put in your diffs have to have a little bit of slippage or eventually you are going to snap your axle(s). ARB air lockers have very little slippage or none at all but can be engaged and disengaged. Also without the diffs in a vehicle or having a "solid" axle your tires are going to wear more when you go around curves. I know a lot of people that have used Detroit lockers and do not like them cause if they fail to allow the slippage they say it isn't long before the axle snaps. I have a '94 JGC Limited and it is full time 4WD and everything spins just the same as a part-time 4WD and take it mudding as I would any other vehicle, I have only options on transfer selector for Full Time 4WD, neutral, and Low Range 4WD. Of course I have never seen a cause for using low range YET. I go mudding, not rock crawling.

At certain highway speeds a full-time transfer case may release allowing better MPG though. I have had mine up to 85 MPH when stuck in a mud hole and my front left and right rear(sometimes the left rear would spin also) were still spinning. Part-time can also be ran on the highway if you need it and don't mind the MPG.

[msdz]

Originally Posted by fredjacksonsan

Full Time leaves the transfer case unlocked, so the front and rear can turn at different speeds.

After reading and also talking to a certified Chrysler mechanic(buddy) I was told and read what is described as a sensa-trac or traction control(can't remember actual name, I believe this is a GM term) which has nothing to deal with the transfer case or transmission. It relies on the computer, wheel sensors, and Anti-Lock Brake System. When the wheel is starting to slip or spin then the wheel sensors send information to the computer that it is spinning or slipping, which then the computer sends a signal to the ABS system to apply pressure to the caliber through the ABS pump to the specified wheel(s) to regain traction.

The 4WD part-time or full time systems has not change very much for over fifty years and still used on newer vehicles, it is the technology of the ABS that has dramatically improved traction control. Also on older vehicles that people are serious about mudding in without ABS they will have seperate "cutting" brakes. Usually hand operated controls to stop the power being transferred to a certain wheel so the other wheel will get traction.

[wafrederick]

The fulltime 4x4 is only in the ones with a V8.The ones with the 4.0 have the part time 4x4.

[sreilly77]

Originally Posted by wafrederick

The fulltime 4x4 is only in the ones with a V8.The ones with the 4.0 have the part time 4x4.

I have a 98 Grand Cherokee Laredo with a 4.0L and I have the option of 2WD, Part-Time 4WD, Full-Time 4WD, and Part-Time 4WD Lo. The Quadra-Trac 4WD systems are on the Grand Cherokees with the V8 and the Selec-Trac is on the Grand Cherokees with the I6. However you can have the Selec-Trac on either the Laredo model or the Limited model. I have the Selec-Trac. I almost bought a Grand Cherokee Limited with the V8 and it had the Quadra-Trac, however I hear these have a lot of transmission problems. Even this one that I was about to buy had the transmission replaced and it only had 84,000 miles on it.

You are also not supposed to use Part-Time 4WD on dry surfaces. It says it in big bold letters in the Owner's Manual. Part-Time 4WD is only use in Low Traction situations such as mud and heavy snow. Full-Time 4WD can be used in any condition. If you want ALL the wheels to spin, then either A. Buy locking differentials and install them with the proper transmission and transfer case or B. Buy a vehicle that has ALL WHELL DRIVE (AWD). That is the difference between AWD and 4WD. AWD is where every tire receives 100% power ALL THE TIME and usually has a V8 engine (such as the Ford Explorer Limited/Eddie Bauer Edition). 4WD is where two wheels spin at the same time: either the REAR right wheel or FRONT left wheel or vice versa. Depending on which direction the front wheels are pointing or what gear you are in (reverse or drive) decides what wheels spin when.

[wafrederick]

The models with the fulltime 4x4 are gas hogs because of the fulltime 4x4

[msdz]

OK, EXPLAIN how a transfer case is going to tell the difference between full or part time 4WD? IT DOESN'T!!!! The transfer case is either in or it isn't, plain and simple. Now the difference that I might see is.... part time 4WD will possibly engage some other system(vacuum or electronically) for the differentials, locking them to allow almost a TRUE 4WD(have heard about this on some Jeeps, will check around though, not sure though). Full time does not have this option, I guess. Part time CAN be ran on hard surfaces providing that is does not lock the diffs together for the front axle, steering the front wheels can possibly break the axle with a "locked" diff. I had a '86 Chevy 3/4 ton 4WD that the front differential locked after the one front wheel would freely spin(limited slip), it did not lock instantly after putting the transfer case in part time though. In order to steer with out forcing it I would have to back up about 2-5 feet to disengage the locked diffs. Also had bent the rear driveshaft in the old truk and took it out and locked in the transfer case and drove it around with just the front tires pulling me for about 10 months till I got a new rear drive shaft.

Also AWD is the same just another fancy name for 4WD. All 4 wheels CAN NOT receive power at the same time under normal driving conditions for the same reason as I stated before, the front axles will not hold due to the difference of each front wheel travelling a different distance. One wheel would be trying to spin faster than the other in a turn which is 1: going to wear the hell out of the front tires or 2: snap an axle, it may not do it the first time, but eventually it will cause the axle to get weaker.

Oh, I do not consider my '94 JGC Limited with full time 4WD to be a gas hog, not at 22 MPG highway.

[sreilly77]

Originally Posted by wafrederick

The models with the fulltime 4x4 are gas hogs because of the fulltime 4x4

That's exactly why I bought the Laredo. I mean yeah it doesn't have all the bells and whistles as the Limited but GAS IS GOING UP YET AGAIN! Another reason is I would much rather prefer to control the 4WD myself instead of the computer making all the adjustments. Plus, between the Laredo with the Selec-Trac and the Limited with the Quadra-Trac, my Laredo rides MUCH better than the Limited I test drove. The Limited was way too stiff.