Diff transfer cases

[_UnLiMiTeD_]

Well all the other liberty's i test drove had the 4wd part time option only, this renny i bought has a full and part time option. Was this the better quality case out of the two or has it had more problems?

 

[Corwyyn]

Can't really recall anyone complaining about the Command-Trac transfer case (the one you have). Most seem to think it's nice to be able to leave it in 4WD full-time. Guess if I had one I'd do that also, but then again probably not - we really don't have much call for it out here in the desert southwest...

 

[tjkj2002]

Well all the other liberty's i test drove had the 4wd part time option only, this renny i bought has a full and part time option. Was this the better quality case out of the two or has it had more problems?

The select-trac(NV242) t-case you have is able to drive on hard surfaces in 4wd all the time due to having a diff in the t-case,the other t-case offered is the command-trac which you can only use 4wd on loose surfaces to prevent driveline bind and breakage.The select-trac is a weaker t-case then the command-trac but you should be just fine.

 

[Corwyyn]

Thanks tjkj, can't remember my command-tracs from my select-tracs

 

[_UnLiMiTeD_]

thanks guys. This one just feels real different. The black one i test drove had a locker because when i turned sharp in 4wd the tires were spinning when i wasnt even giving any gas.

 

[JeepJeepster]

Yea, its not good at all to use part-time 4wd like you did in the 'black' one. That causes driveline binding which puts more wear and tear on cv joints and ujoints among other things. I wouldnt do that anymore.

 

[_UnLiMiTeD_]

lol yea it was beat to shit anyways, but i wont do that in my rene. But while off roading , you do have to take some harder turns, how much do you recommend i turn before i should worry. Never had an suv or been an off roader, all new to me

 

[MoladoGuy]

As long as you are on some type of ground that can give way when the wheels turn (sand, mud, gravel, snow) you shouldn't worry too much about turning radius. HOWEVER, you should rarely need to turn with full lock while in 4-Lo or off-road unless your trying to do donuts in an open field.

 

[JeepJeepster]

Sorry, I forgot to say that you shouldnt use part-time on hard surfaces such as blacktop.

Its ok to use it as long as the wheels can slip. IE, dirt roads, gravel roads, snow, ice, mud, etc.

 

[turbodave]

The select-trac(NV242) t-case you have is able to drive on hard surfaces in 4wd all the time due to having a diff in the t-case,the other t-case offered is the command-trac which you can only use 4wd on loose surfaces to prevent driveline bind and breakage.The select-trac is a weaker t-case then the command-trac but you should be just fine.

This is interesting to me - I was naievly under the impression that domestic vehicles with 'real' 4x4 systems (ie with transfer cases) didn't have the centre diff. I do find it surprising that you can spend $50K+ on a pickup and get a non-centre diff transfer case for example.
So - just out of interesat what larger vehicles / pickups have transfer case options with the centre diff?
I should add - I'm a relative newbie to the USA; coming from the UK where centre-diffs have beem on rangerovers since 1970 and all defenders since '84... That I could get one in a liberty is VERY interesting!!!

 

[tjkj2002]

This is interesting to me - I was naievly under the impression that domestic vehicles with 'real' 4x4 systems (ie with transfer cases) didn't have the centre diff. I do find it surprising that you can spend $50K+ on a pickup and get a non-centre diff transfer case for example.
So - just out of interesat what larger vehicles / pickups have transfer case options with the centre diff?
I should add - I'm a relative newbie to the USA; coming from the UK where centre-diffs have beem on rangerovers since 1970 and all defenders since '84... That I could get one in a liberty is VERY interesting!!!

Jeep(still AMC then) had a t-case with a diff in it since the early '70's with the Quadra-Trac t-case,and has upgraded the Quadra-Trac to the Quadra-drive and Quadra-driveII.

 

[Atrus]

Can you technical guys edumacate me a little bit?

I understand that the select-trac has a front differential just as the rear does. My question is, where is this? Is it in the actual transfer case, or is it in the front axle? I just don't see how it can be in the T-case since there's just a regular driveshaft heading up to the front axle, right? Or are the KJ's with the IFS different? I am picturing it on a SFA - with my skids, I really haven't had a great opportunity to check out the KJ's setup.

Additionally, in 2wd the rear has an open diff (not a posi?) - therefore, the side with less resistance will spin. Is this true for the front in Full Time and Part Time? Or in Part Time, is the front locked so both wheels spin equally, and the rear still is "one wheel drive?"

 

[turbodave]

In the same way as you need a cross-axle differential because the outside wheels travel a greater distance than the inside wheels during a turn, Ideally you also need a diff between the front an rear axles because the front axle is travelling a greater distance than the rear during a turn... Hence - there is a diff mounted in the transfer case to distribute the drive. It might not look like a conventional diff because there are many ways to achieve this (ball, epicyclic, spur gear, etc..), but there wil be one in there!

The advantages (for a centre diff) are many - and perhaps the only disadvantage is that all four wheels are driving, hence compared to a 'traditional' 2/4wd-hi /4wd low transfer case with front free-wheel hubs, is always driving all axles, shafts, hubs, tyres, etc. The traditional vehicle can of course completely isolate the front axle with the above.

Advantages are that you don't need a monster back axle for towing, because you have drive to all four wheels on sealed surfaces. Of course, if one wheel slips, all movement stops as all the drive escapes through the loose wheel. The balanced tyre wear and control in loose (or loose/sealed combination) surfaces is better than a vehicle in 2wd of course.
If you have a centre diff - it is important that this can be locked - and when it is, it needs a front and a rear tyre to break traction for drive to be lost (otherwise just one wheel will spin, losing drive).




So - is the Jeep transfer case (or any of the others you mentioned) electronically controled, or are they still basically manual internals? I.E. - could you get them to work in a vehicle that wasn't factory fitted with one?

 

[Atrus]

So - is the Jeep transfer case (or any of the others you mentioned) electronically controled, or are they still basically manual internals? I.E. - could you get them to work in a vehicle that wasn't factory fitted with one?

I believe they are just manual - I think you can interchange the two transfer cases easily. For clarification too, the Select Trac has all the options of the Command-Trac, plus "AWD"....I have 2 Hi, 4Hi Part Time, 4Hi Full time, Neutral, 4Lo on my selector.

I suppose I am still not understanding. What I am picturing is the rear axle has the diff in it - so each rear wheel can move independantly. As you said, in a turn this is necessary so you don't bind. Like in a car with a locker, you'd wheel hop the rear on a turn.

In a traditional SFA, the front is set up similarly...diff in the middle with a driveshaft to the Transfer case.

So, are you saying that all Jeeps have a front diff, and the reason for the Select Trac transfer case having the diff is not to "seperate" the wheels left to right, but to seperate the front-to-rear?

So, in part-time 4Hi, or 4Lo for that matter, we truly have two wheels driving? That'd be the reason some want a locker?

What I am not understanding then, based on what you said Dave, is that with a center diff setup, it's constantly in 4 wheel. That's not the case with the KJ - you can go into 2wd. Full time 4wd would put you at 48% power to the front, 52% to the rear. So, I would assume the center (transfer case) diff is more of a posi unit? Otherwise, what would be the point? - As soon as one tire slipped, all power would be put to that wheel. There'd be no 4wd advantage.

 

[Dave]

The thing to remember is with either the command trac (part time) or selec trac (full time) when you go into 4wd and have open diff's you actually have the left front and right rear wheels driving. So you could say you have 2 wheel drive. Now with a locker in the rear you have both rear wheels driving and still only the left front unless you put a TT or something in the front, and then all 4 wheels driving.

Dave

 

[Paine]

Part or Full

A few contradictions through this thread, trying to stay with the lead here.

If your in Part-Time 4wd, why would you need to be on a loose surface? Doesn't it grab once it hits the loose surface (on-demand)?

 

[tjkj2002]

I believe they are just manual - I think you can interchange the two transfer cases easily. For clarification too, the Select Trac has all the options of the Command-Trac, plus "AWD"....I have 2 Hi, 4Hi Part Time, 4Hi Full time, Neutral, 4Lo on my selector.

I suppose I am still not understanding. What I am picturing is the rear axle has the diff in it - so each rear wheel can move independantly. As you said, in a turn this is necessary so you don't bind. Like in a car with a locker, you'd wheel hop the rear on a turn.

In a traditional SFA, the front is set up similarly...diff in the middle with a driveshaft to the Transfer case.

So, are you saying that all Jeeps have a front diff, and the reason for the Select Trac transfer case having the diff is not to "seperate" the wheels left to right, but to seperate the front-to-rear?

So, in part-time 4Hi, or 4Lo for that matter, we truly have two wheels driving? That'd be the reason some want a locker?

What I am not understanding then, based on what you said Dave, is that with a center diff setup, it's constantly in 4 wheel. That's not the case with the KJ - you can go into 2wd. Full time 4wd would put you at 48% power to the front, 52% to the rear. So, I would assume the center (transfer case) diff is more of a posi unit? Otherwise, what would be the point? - As soon as one tire slipped, all power would be put to that wheel. There'd be no 4wd advantage.

If you have the select-trac t-case you have 3 diffs,one is the front axle,2 is the rear axle,and the 3rd is inside the t-case.The center diff in the NV242 t-case is not a "posi" unit,just a regular open diff.

PaineA few contradictions through this thread, trying to stay with the lead here.

If your in Part-Time 4wd, why would you need to be on a loose surface? Doesn't it grab once it hits the loose surface (on-demand)?confused.gif

The command-trac t-case(231) has no center diff,so the front and rear axles turn at the same speed,hence the reason you can't use it on a hard surface,you can but the speed differences from the F/R driveshafts will cause bind and you'll either "hop" the tires or break something.The "part time" stands for you only use it part of the time when extra traction is needed,"full time" means you can use the 4wd all the time.

Also just to clarify in all 4wd vehicles the front and rear diff gearing is not the same,even though they say they are and advertise them as the same they are not.Like my 4.10's I have now,the rear gears are true 4.10:1,the front's are 4.09:1.When I do my SFA I'm going to 5.13's,the front will be true 5.13's and the rear will be 5.14's even though the rear gears are sold as 5.13's.The reason for this is so the front wheels will spin slightly faster then the rear tires,it keeps you going straight in mud and loose conditions.It is fact.

To counter this try airing down your front tires to say 18-20 psi and pump the rear's to 40psi then hit some slick mud,the rear will come around so fast you won't know what happened,and you will not be able to keep it straight.After that put the tires at the same psi and you'll still be all over the place but for the most part be pretty straight.The gearing difference is just enough to help but not enough to cause alot of damage.

 

[Atrus]

Thanks for clarifying TJKJ. I still don't understand....

Ok, so there is an "open" diff in the front, one in the rear, and one in the center when in fulltime, and it's "locked" in part time.

This would mean that if we look at the front and rear axle independently - when one wheel encounters less resistance, that's the wheel that will spin.

If there's an open diff in the transfer case, I would assume it works the same way - if one axle loses traction, then that is the axle that power is applied to.

So, let’s say we’re on ice in the winter. You’re in full time 4wd. Wouldn’t it end up that the wheel with the lowest resistance would spin while the other three wheels are doing nothing? In part time, wouldn’t you end up with 2 wheels spinning (one per axle) while the others just do nothing? I can see where there's still a benefit to part time in that scenerio, but I don't see how full time 4wd helps anything at all.

 

[_UnLiMiTeD_]

.....my head hurts....