Jeep Cherokee Talk banner

1 - 20 of 34 Posts

·
Registered
Joined
·
79 Posts
Discussion Starter #1
When i have my four wheel drive engaged, is it common for the steering to be effected? When i would take a tight turn, such as into a parking space, it feels like my front end is "hopping" across the ground. When i turn off my four wheel, its back to normal. Is this normal?
 

·
Retired Moderator
Joined
·
7,287 Posts
Yes, what you're feeling is the drivetrain binding. What selection are you putting your tcase in, Part-Time or Full-time? You most likely have the Selec-Trac transfercase (NP242), which means that you have 2-4Part-Time-4Full-Time-N-4Lo. If you use 4Part-Time on any hard or dry surface (even rain isn't slippery enough), then you're not allowing your axles to slip so you'll feel them bucking and "hopping." 4Part-Time splits the power evenly (50-50) between the front and rear axles, and is intended for terrain such as thicker snow, sand, mud, loose gravel, etc.

4Full-Time is designed so that 52% of the power is sent to the rear and 48% is sent to the front, which allows the axles to spin at different speeds. This will make turning feel more normal, and it reduces binding significantly.

My rule of thumb is if you can see pavement or road striping, use Full-Time, if you can't see the pavement and/or the striping then you can use Part-Time if you so choose. I always found that Full-Time was sufficient for most snowy conditions.
 

·
Premium Member
Joined
·
1,629 Posts


There are two large gears in the transfer case connected by a large heavy chain. When you feel that hopping, you are putting a great deal of stress on that chain. The chain will stretch and eventually you will hear a popping noise as the chain jumps over the teeth of the gears. No more 4x4 action.

If you have a FULL TIME selection use it for on road (and off is fine too) 4x4.

Part time is meant ONLY for very slippery areas. Mud for example, dirt I suppose, pretty much anything slippery enough or soft enough to let the tires slip.

This is one of the reasons I like the NP242 transfer case so much, as it allows me to actually USE my 4x4 anytime as opposed to just using it off road.
 

·
Budget Master
Joined
·
1,145 Posts
yes very common.
 

·
Registered
Joined
·
79 Posts
Discussion Starter #5
Ahh, thank you. That makes sence now. I did, in fact have it on Part time 4x4. On the display where it shows the diagram of the drivetrain, on the left it says what transfer case selection your in. My other question is, whats on the right side? I parked in the sun one time, and say the outline of a shape, but could not figure out what it was.
 

·
Registered
Joined
·
37 Posts
i dont understand the whole "part time 4 wheel drive". i am somewhat new to jeep's but my 95 GCL auto. when i put it in 4 hi it says part time. i dont know what happens when you put it in 4 low. when you put it in 4 hi and it says part time does that mean it only engages when it senses the jeep needs it, or what?
 

·
Registered
Joined
·
1,951 Posts
Part time 4 hi SHOULD only be used offroad or under extemely slick conditions. Full time can be used anytime anywhere. When in part time the front and rear are locked together. In fulltime it is a 48/52 split from front to rear and the front is not really locked in,allows some give (for lack of a better term). 4lo should be used for offroad conditios where you need to creep along
 

·
Premium Member
Joined
·
1,629 Posts
It's pretty neat how it works.

In 2wd HI you are in normal everyday "car" type driving. Rear wheel drive.

In 4wd Full time power is sent to the rear wheels and the front wheels, but the front axle and rear axle can turn at different speeds. This is great for making turns since the outer front wheel will turn more rotations, than the inner front wheel.

In 4wd Part time power is sent to the rear wheels and front wheels, just like the Full time, however now the front and rear axle are locked together. So when you make turns on high friction surfaces, like a paved road, the front tires will "chirp" or hop because the rear tires are spinning at a different rate. Something has to slip to make up the difference in wheel rotation speed, or a mechanical failure will occur.

In 4wd part time low, you are just changing the gearing to a much lower ratio. All the same things apply to the 4wd part time above, but now your engine will rev much higher and apply more torque to the ground. This is great for crawling over and up things. Max speed is about 20 miles per hour, and the engine is screaming at that speed.

I'll go one step further.

When in 4wd part time the front and rear axles are locked together. Power is being sent from the engine to both axles. Open differentials only apply power to one wheel on each axle. There are limited slips in some rear differentials, so the best traction you can hope for is 2 wheels (1 front, 1 rear) and some traction on the other rear wheel. In effect you have a 3 wheel drive!

Now this is great compared to cars that in effect are 1 wheel drive. They have they same time of open diff as well. Some have limited slip, etc... but the effect really is power to one wheel.

This is where "lockers" come into play. If you add a locker to your rear axle (diff) you now have full power going to 3 wheels. Add another locker to the front axle (diff) and you now have full power going to all 4 wheels!

You can well imagine that if 4wd part time (locking front and rear axles) will make your tires chip, a front locker certainly will. Not only are the two axles locked but now your two front wheels are locked to each other, and the rear wheels locked to each other. So, each of the 4 wheels are LOCKED to each other! That is rotational power being delivered to EACH wheel. I know you thought that was happening already, but it isn't.

Go to youtube and watch some of the off road videos. Usually the rigs that aren't built up you'll notice one of the wheels isn't spinning. That means it isn't locked.

This is my ultimate goal. Selectable front and rear lockers. There are various tweaks you can do to this setup but in reality a fully locked 4x4 is as good as it gets. If you wanted something better you'd need to attach legs to your Jeep!

 

·
Registered
Joined
·
79 Posts
Discussion Starter #9
That was a great explaination!
I never knew the details about how it all worked.
 

·
Premium Member
Joined
·
1,629 Posts
That was a great explaination!
I never knew the details about how it all worked.
I didn't either until a couple of years ago. It was funny. After I found out I was all excited and explained it to my wife and my two girls. You can imagine the eye rolling that went on, but I told them ALL about it.

 

·
Registered
Joined
·
79 Posts
Discussion Starter #11
Haha.
That sounds easier to explain, than to when i explained to my mom that i want to put Neons on my jeep haha.
 

·
Retired Moderator
Joined
·
7,287 Posts
In 4wd part time low, you are just changing the gearing to a much higher ratio. All the same things apply to the 4wd part time above, but now your engine will rev much higher and apply more torque to the ground. This is great for crawling over and up things. Max speed is about 20 miles per hour, and the engine is screaming at that speed.
Mudd, great and thorough explanation. Just want to comment on the above. The gear ratio becomes numerically higher, which means that it is "lower" gearing. 4:1 ratio is "Lower" than "2.72:1" even though it is numerically higher. Not that what you said was wrong, but that for those newer to this sport, that can be confusing.
 

·
Premium Member
Joined
·
1,629 Posts
Mudd, great and thorough explanation. Just want to comment on the above. The gear ratio becomes numerically higher, which means that it is "lower" gearing. 4:1 ratio is "Lower" than "2.72:1" even though it is numerically higher. Not that what you said was wrong, but that for those newer to this sport, that can be confusing.
Hmmm looks fine to me. :dunno:

Ummm pay no attention to that "edited information". ;)
 

·
Registered
Joined
·
79 Posts
Discussion Starter #14
For some reason i think ive been using my jeep differently than most of the members of this forum haha. I hope im not offending you guys :/
 

·
Premium Member
Joined
·
1,629 Posts
Haha.
That sounds easier to explain, than to when i explained to my mom that i want to put Neons on my jeep haha.
Get the LEDs. They won't break, and they even call them "rock crawling" lights. You can be cool, but still have the plausible deniability! :rock:

 

·
Budget Master
Joined
·
1,145 Posts
yep those are cool.
 

·
Registered
Joined
·
37 Posts
thank you. for explaning that for me. i actually understood alll of that. haha. i have been told about this for ever and never understood it untill now. thank you
 

·
Premium Member
Joined
·
1,629 Posts
thank you. for explaning that for me. i actually understood alll of that. haha. i have been told about this for ever and never understood it untill now. thank you
Oh crap! I didn't notice you had a "GRAND" cherokee. The 4x4 system works completely diffrent on those. Sorry, you may want to trade it in and get an XJ.






 

·
Registered
Joined
·
79 Posts
Discussion Starter #20
I also had another Problem last night with my Grand Cherokee. You know how you said to only use my Part time 4x4 on certain surfaces? Well i started my jeep to go to work, then i made sure it was in 2 wheel. I back up, cut the wheel and it starts to "hop" again. I thought i might of turned it a little hard so i thought nothing of it. I started ti drive and i heard the sound the front drive shaft makes when its engaged. This isnt the first time this has happened. When i got off work, and drove it home it was back in 2 wheel. Why dosent my four wheel turn off right away?
 
1 - 20 of 34 Posts
Top