4-part time vs. 4-full time

[ephantmon]

Yes, I've read the owner's manual about HOW to engage them/disengage them etc. I'm still unclear though about when/why you would use part time 4wd instead of full time?

 

[kjpilot]

You can use full-time any time, all the time if you want. Part-time is only to be used when on loose material like gravel, dirt, & deep snow. Since you have full-time, I'd say only use part-time if you are actually off-road or in one heck of a snow storm, otherwise use full-time or 2WD.

 

[Atrus]

Only time I use part-time if in enough snow or mud that I am constantly in it - i.e., snowstorm or a completely muddy trail.

Otherwise, I use full-time as I figure any binding, even minimal, is worse than none. So, light or intermittant patches of snow or mud, offroading on dry surfaces, etc I will use full-time.

 

[maddawg]

well i have a 07 sport and all i have is 4 lo and hi.......so i would just use this off road correct

 

[kjpilot]

well i have a 07 sport and all i have is 4 lo and hi.......so i would just use this off road correct

Or in a winter storm where the roads are completely snow or ice covered. I Don't know how often that happens in Raleigh, NC though.

 

[Atrus]

well i have a 07 sport and all i have is 4 lo and hi.......so i would just use this off road correct

That means you have 4lo and 4-part-time. You are correct in your thinking - your tires need to be able to slip - so, gravel, snow, mud, etc.

Dry (or just wet) pavement is a big no.

For the select-trac bunch, we have 4lo 4PT and 4FT (full time) - 4FT allows you to drive even on dry pavement with no ill effects.

 

[CHUD]

I'm still unclear though about when/why you would use part time 4wd instead of full time?

I would surmise that since part-time 4WD mechanically locks the front & rear axles (which will cause binding & hop on dry pavement) this mode would offer a bit better traction on the slippery stuff than the viscous coupling on the full time 4WD, which allows slippage. I like to use the part time 4 on surfaces that have yet to be plowed.

 

[kjpilot]

There is no viscous coupling in the NP-242 (selec-trac) t-case. it acts like an open differential, only between the front & rear wheels.
The Grand Cherokee's Quadra-trac uses the viscous coupling.

The problem using Part time when it's just slick in spotty areas is you hit a lot of dry pavement as well. When the road is totally snow packed, then part time is better, but as soon as the plows start to come through, it's full-time. My experience on icy roads is that full-time is quite a bit more stable.

 

[JeepJeepster]

Part-time locks the front and rear drive shafts together so that they spin at the same speed. Since the front and rear wheel spin at different speeds when you turn the wheels need to slip when you turn in part-time. When youre on hard surfaces this isnt allowed to happen so torque builds up through-out the driven train then, BOOM, some breaks.

Some people also say that the front and rear gear ratios are not exactly the same so the front and rear axles spin at different speeds all the time.

 

[tjkj2002]

Some people also say that since the front and rear gear ratios are not exactly the same the front and rear axles speed at different speeds all the time.

The front and rear axles are not geared the same.The front axle is just slighlty geared higher as so the front wheels spin just a tad faster to help keep your rear end from trying to pass the front end on slippery surfaces.

They may be labeled the same rato but they are not.I put 4.10's in my KJ,the rear gears are actually 4.10's and the front gears are actually 4.09's.The same goes for my new axles,they are labeled 5.13's but the rear axle is actually 5.14 with the fronts being the actual 5.13 ratio.

 

[LibertyFever]

The very first time I drove my Libby Sport automatic in 4WD (part-time) I was surprised how the tires would "scrub". It was the first time I ever drove a 4WD.

While driving on the snow & ice covered highways I'll slip in and out of 4WD Hi as needed but while on the trails I keep it in 4WD Lo and in 1st or 2nd.

Sometimes I'm glad I don't have part & full time 4WD. I hate making decisions

 

[Atrus]

Main reason I got FT4WD - so I can put it in FT and my wife can drive it wherever. If she had to switch it in and out, she'd end up binding it all the time.

 

[J-Thompson]

I could not tell you if 4wd part time ,high range, works on either Jeep
I know that 4lo works on both and 4FT works on the KJ
We have never seen a need for 4wd high

 

[JeepJeepster]

I could not tell you if 4wd part time ,high range, works on either Jeep
I know that 4lo works on both and 4FT works on the KJ
We have never seen a need for 4wd high

Gosh, I have. Anytime Im offroad Ill keep it in that till I need to crawl up something. Its also good for mud when you need to get the tires spinning... I stay away from mud so thats not always needed.

 

[tjkj2002]

JeepJeepsterQuote:
Originally Posted by J-Thompson
I could not tell you if 4wd part time ,high range, works on either Jeep
I know that 4lo works on both and 4FT works on the KJ
We have never seen a need for 4wd high

Gosh, I have. Anytime Im offroad Ill keep it in that till I need to crawl up something. Its also good for mud when you need to get the tires spinning... I stay away from mud so thats not always needed.

As soon as I hit the trailhead my KJ goes into 4lo,I never use 4hi unless on snow/ice.

 

[Ry' N Jen]

As soon as I hit the trailhead my KJ goes into 4lo,I never use 4hi unless on snow/ice.

Not out here! Leave it 2wd until you can't move for or aft, then 4hi. and once again until you cannot go foreward. Then you sellect 4 low.
After that it's winch time or recovery!

 

[Bashgod]

i use 4hi when im turning on wet rainy roads with the traction control off. i almost got hit when it kicked in, over a little wheel slip (it was my inside rigt rear tire, of course its gonna spin a little) it decided to give me power in small increments leaving me crawling while entering a highway... so once im out of the turn it goesback into 2hi. can it reasonably be done to swap my T.C. for the better one?

 

[Atrus]

can it reasonably be done to swap my T.C. for the better one?

"better" is a relative term. From what I have read on here, the Command Trac transfer case (2Hi-PT4-N-4Lo) is stronger than the Selec-Trac (2Hi-4PT-4FT-N-4Lo). The Selec-Trac gives the FT option though.

I'd say it's as easy and reasonable as pulling the TC for an overhaul. Price just depends on what you can find a Selec-Trac TC going for. You'd just need the case and the lever. Not sure what would need to be done in the dash so the lights work properly. That's not essential to operation though, so I don't see it as a big deal if the 4FT light never works. I'd actually assume it'd work fine with the "new" TC anyway.

Anyone else with Selec-Trac think it's a little wierd that from 2Hi you have to go into 4PT before 4FT? I would think they would have found a way to have them reversed. Not sure how the selecter works in the case, so maybe it's impossible or just not feasible for the cost.

 

[Bashgod]

It is relative, but seeing as I do no real off-roading and I might be better suited with the Selectrac. we'll see though.

 

[Dave]

Atrus, me too. I wondered about that also. That is how they are all set up so I can just guess that it must be a mechanical thing (mechanical reason) . When I engage mine I pull the lever straight "through" 4pt and stop in 4 ft so I always wondered if not stopping the lever in pt doesn't engage it anyway. You are just pulling the lever "through it" with a fluid motion. I don't know if I am explaining that right. It does seem backwards though. I use mine all the time and have not had any problems with it.

Dave