Is selec track (or full time 4WD) inherently bad or weaker?

[Labswine]

Also - so all this talk about on road performance. Which is great of course. But how well would this transfer case hold up to actually being in 4H or 4L when truly off road? Does it actually 'lock' via gear into 4H or 4L? or is it still powered by viscus clutch like when it is in 4-auto? I think that makes a big difference? For someone strictly on road, then maybe no big deal but for some looking to be in situations requiring full use of 4H/L then strength and integrity would be important.

In 4FT, it's a hard lock front to rear and the shafts and axles will turn together. In 4PT, it's a viscous coupling that allows a little slip between the front and rear so no binding on dry pavement PLUS, and this is the total advantage of it, it detects slippage from either drive shaft and transmits the power to the one that is NOT slipping.

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[jsalbre]

In 4FT, it's a hard lock front to rear and the shafts and axles will turn together. In 4PT, it's a viscous coupling that allows a little slip between the front and rear so no binding on dry pavement PLUS, and this is the total advantage of it, it detects slippage from either drive shaft and transmits the power to the one that is NOT slipping.

This is not correct. There is no “full time” mode for starters.

In 4 Auto the clutch pack (not a viscous coupling) engages in varying levels depending on how much torque it needs to send to the front. No slip, no torque. In 4 High (part time) and 4 Low the clutch pack is engaged fully and it allows no slip. There is no “hard lock” or gear engagement in the MP3022 transfer case. The system cannot “transmit power to the one that is not slipping”, it can only change (from 0-50%) how much torque goes to the front axle. The rear will always be engaged. It also does not transfer torque side to side.

Unfortunately this t-case is not like the old NV242 that had a planetary center differential allowing true full time 4wd, and a geared lock for that differential for 4Hi and 4 Lo.

 

[Labswine]

This is not correct. There is no “full time” mode for starters.

In 4 Auto the clutch pack (not a viscous coupling) engages in varying levels depending on how much torque it needs to send to the front. No slip, no torque. In 4 High (part time) and 4 Low the clutch pack is engaged fully and it allows no slip. There is no “hard lock” or gear engagement in the MP3022 transfer case. The system cannot “transmit power to the one that is not slipping”, it can only change (from 0-50%) how much torque goes to the front axle. The rear will always be engaged. It also does not transfer torque side to side.

Unfortunately this t-case is not like the old NV242 that had a planetary center differential allowing true full time 4wd, and a geared lock for that differential for 4Hi and 4 Lo.

Then they've changed it from the old reliable NV242 that I had in two of my 7 Grand Cherokees (the '96 and the '03).

I stand corrected

 

[chorky]

This is not correct. There is no “full time” mode for starters.

In 4 Auto the clutch pack (not a viscous coupling) engages in varying levels depending on how much torque it needs to send to the front. No slip, no torque. In 4 High (part time) and 4 Low the clutch pack is engaged fully and it allows no slip. There is no “hard lock” or gear engagement in the MP3022 transfer case. The system cannot “transmit power to the one that is not slipping”, it can only change (from 0-50%) how much torque goes to the front axle. The rear will always be engaged. It also does not transfer torque side to side.

Unfortunately this t-case is not like the old NV242 that had a planetary center differential allowing true full time 4wd, and a geared lock for that differential for 4Hi and 4 Lo.

Ok so I take this to understand that the Selec-Trac is actually weaker than the standard 2H, 4H, 4L transferase. Correct? I don't see how clutches in the Selec-Trac could be stronger. Or maybe 'better engaged' would be a better term. So for someone who would plan to truly use 4X4 - the standard transfer would seem to be the better choice.

 

[jsalbre]

Ok so I take this to understand that the Selec-Trac is actually weaker than the standard 2H, 4H, 4L transferase. Correct? I don't see how clutches in the Selec-Trac could be stronger. Or maybe 'better engaged' would be a better term. So for someone who would plan to truly use 4X4 - the standard transfer would seem to be the better choice.

The most accurate answer is “it depends”. Lots of people and vehicles out there using the MP3022, including Liberty’s from ‘08-12, the Wrangler 392, and a number of Hemi Grand Cherokees and Durangos.

Some people have had issues with the clutches overheating while running in beach sand, but those were mostly running in auto mode, meaning the clutch was slipping. That’s really all the issues I’ve heard about it. If you use it offroad just put it in one of the locked modes and expect you’ll never have a problem. The CV joints in the front axle shafts are arguably much stronger than u-joints as well.

 

[chorky]

If you use it offroad just put it in one of the locked modes and expect you’ll never have a problem.

So what does this actually mean though? Is there a straight up gear lock like a 'standard' 4wd x-fer case? Or does it just apply high pressure to the clutches to make them seem locked?

I called a service department today to ask the same question and they couldn't really answer me. Aside from saying they haven't had any failures (which is good news). but I would still like to know how it actually physically functions internally. Tried looking up some schematics and didn't find much so will continue that search today.

The concern I would have is even if the clutches are pressed together very hard it still is not a true 4x4 LOCK. That would cause issues in actual 4x4 situations I think. Think of a differential lock on the Rubicon or ARB or any other diff locker. When it's locked, it is flat out locked. Zero opportunity for slippage unless something breaks. I guess I just don't see a clutch system being able to do that in true 4x4 situations. It would be super awesome if this x-fer case did have the normal clutch pack for AWD, but then had a true lock for 4H / 4L. I am not however seeing any documentation that really explains its internal operation. The reason for my concern about this is if on a trail and needing full power to both axles equally, will this system deliver? Or will it only be strong enough to put a percentage of the power to the front wheels, or if the front wheels suddenly grabbed traction, would the clutches in the x-fer case slip causing a loss?

 

[jsalbre]

So what does this actually mean though? Is there a straight up gear lock like a 'standard' 4wd x-fer case? Or does it just apply high pressure to the clutches to make them seem locked?

I called a service department today to ask the same question and they couldn't really answer me. Aside from saying they haven't had any failures (which is good news). but I would still like to know how it actually physically functions internally. Tried looking up some schematics and didn't find much so will continue that search today.

The concern I would have is even if the clutches are pressed together very hard it still is not a true 4x4 LOCK. That would cause issues in actual 4x4 situations I think. Think of a differential lock on the Rubicon or ARB or any other diff locker. When it's locked, it is flat out locked. Zero opportunity for slippage unless something breaks. I guess I just don't see a clutch system being able to do that in true 4x4 situations. It would be super awesome if this x-fer case did have the normal clutch pack for AWD, but then had a true lock for 4H / 4L. I am not however seeing any documentation that really explains its internal operation. The reason for my concern about this is if on a trail and needing full power to both axles equally, will this system deliver? Or will it only be strong enough to put a percentage of the power to the front wheels, or if the front wheels suddenly grabbed traction, would the clutches in the x-fer case slip causing a loss?

There is no gear lock in the Selec-Trac transfer case. It is wet clutch only. That said, there are much more powerful engines than you can get in a JT attached to it without issues. If you can overpower a multiplate wet clutch you’re putting down some immense power.

The MP3022 is rated by Magna Powertrain for 800-1000 nm of torque. That converts to about 590-740 ft-lbs. unless you e got a blown V8 you’re probably fine.

Edit: removed the MP3023 info as I found the actual specs for the 3022.

 

[Sting-Gray Neutral Pres.]

Also remember that even fully locked unless you are in some bizarre situation where you have perfect traction in the front and zero traction on both rears (because Selec-Trac comes with a rear LSD), less than full engine torque will be applied through the locked clutch to the front driveshaft.

Honestly though if for some reason it did slip a bit while doing something extreme/fun/hold my beer in 4Lo that's probably preferable to a geared transfer case exploding out in the sticks.

 

[Snake Eyes]

I got mine without 4WDAuto. Alot of people talk about the needs for it in wet weather. I have driven a rear wheel drive sports car for 5 years. It is fantastic in rain WITH the right tires. Tires are more important than anything. I drove a rear wheel drive miata in the winter in Idaho with a sand bag in the back and snow tires and I started, stopped and drove better than trucks who were generally overconfident. When I was a cop in Utah I drove a rwd crown vic in the worst weather and with the right tires had not problem. Tires are your first line of defense. Your second is driving according to the weather conditions and not like an idiot. Any vehicle will go right off the road if not driven correctly regardless of whether it is AWD, 4WD, etc. I pulled many 4x4s and AWDs out of ditches when I drove the crown vic fine. Overconfidence is such a bad thing in bad weather….”I have a truck or I have AWD so I can go faster, etc” Who has not seen that in a rain storm to their left…until that vehicle hydroplaned. So 4WD auto was not a necessity for me and can lead to people being overconfident in their vehicles ability on the road. MY 4x4 is for offroad or snow where I really have to go slow. People say you can do 4H at high speeds. Why would you? IF you truly need 4H high speeds are stupid and endanger everyone. I stay in 2WD with appropriate tires unless offroad or slow in snow storms and did so for the 20 or so years I lived in UT, ID and CO (had a TJ in CO). IMHO

 

[Irikumi]

I just got a JT, I am new to Jeeps, but not new to 4x4's. I have had multiple Subarus and 4x4's over the years. I also currently have a UZJ100 Land Cruiser, which is Full-time 4x4 with a lockable center differential and a low range of course. The UZJ100 is pretty outstanding.

I didn't even know there was such a thing as a Full-time transfer-case option on a Rubicon, mine just happens to have it so I have been going down the rabbit hole to learn all I can about it. In-depth info is not really that readily available, but I found some good info here in this post so thanks. It would be cool to strip a MP3022 down and see how well built it is internally. Probably not as stout as my Land Cruisers Full-time transfer case, but as long as it holds up when I wheel it in Moab, then I won't complain. There was a guy on my last trip pushing his 392 Wrangler pretty hard and it seemed trouble free.

Only time will tell how well this fancy MP3022 lasts, I suppose if it ever became a big problem, a guy could opt to put in an Atlas Transfer case. I don't know how well the Atlas would integrate with the electronics built into these newer trucks. Having potential trouble codes pop up would be annoying with an Atlas... But maybe they have all that worked out already. I guess I will cross that bridge if I have to, but for now I will just be happy.

Cheers from Arizona!

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