Someone Explain the Diff. 4wd Systems Please

[desert_freak]

Yes I am new to the 4x4 world and have questions about the different systems offered and their abilities. I want to understand them all before I purchase my first Jeep. Please don't laugh at my questions I have never even used 4wd on a vehicle before.

1. Do all systems have locking hubs that need to be engaged for 4wd and disengaged to freewheel?

2. Which systems(and the years offered on Wags)are able to be engaged from inside the cab (and do you have to lock the hubs first).

3. How are each system engaged (rolling in N 2-5mph, at any speed, etc.)

4. Which systems offered 4low on the Wags and which years.

5. Any other info that may help me better understand the various systems, their operation and their limitations.

I hope this is not the umpteenth time these questions have been asked but I did search the topics for a comprehensive listing but was unable to find one.

From what I have read I think staying away from the NP229 sounds like a good idea. I have read the Tech Article Section for the transfer case listings but don't understnd the difference between the NP-208, NP-219, NP-228, BW-1339.

I understand that the BW-1305 doesn't have low range but does the D20?

I would like to do some 4-wheeling into the back country with the family and friends.

I know it's a huge question but the Engineer in me needs to know research the heck out of everything so I can make an informed decision.

Thanks in advance all.



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[BobBarry]

<BLOCKQUOTE>quote:</font><HR>Originally posted by desert_freak:
Yes I am new to the 4x4 world and have questions about the different systems offered and their abilities. I want to understand them all before I purchase my first Jeep. Please don't laugh at my questions I have never even used 4wd on a vehicle before.

1. Do all systems have locking hubs that need to be engaged for 4wd and disengaged to freewheel?<HR></BLOCKQUOTE>

No; there were three ways the front hubs were engaged:

1. Permanent-Drive hubs, used on QT and Selectrac systems
2. Unlocking hubs, optional for all part-time cases over the years
3. Front Axle disconnect, used on '83-'84 Selectrac models (which disconnected the front driveshaft from turning in 2wd mode.

<BLOCKQUOTE>quote:</font><HR>2. Which systems(and the years offered on Wags)are able to be engaged from inside the cab (and do you have to lock the hubs first).<HR></BLOCKQUOTE>

All could be engaged from inside the cab; only the locking hubs had to be engaged with the D20/D21 and NP208 cases before 4wd could be used. (you *could* engage it without the hubs locked, but you'd only have rwd; as a rule, if you expected to need 4wd, you'd lock the hubs before starting off and engage 4wd as needed.

<BLOCKQUOTE>quote:</font><HR>3. How are each system engaged (rolling in N 2-5mph, at any speed, etc.)<HR></BLOCKQUOTE>

* D20 and D21 were shift-on-the-fly,
* Both QT systems were permanently engaged
* '83-'84 Selectrac models needed to be stopped,
* '85 and newer Selectracs could be shifted into 4Hi at any speed,
* NP208 Command-trac was engaged at a 2-5mph roll, as was the low-range and/or emergency drive on all other cases.

<BLOCKQUOTE>quote:</font><HR>4. Which systems offered 4low on the Wags and which years.<HR></BLOCKQUOTE>

It was optional on the '73-'79 Quadratrac systems, and not available in '63-early'65 with the Borg-Warner automatic that only came with the single-speed D21 transfer case. Other than that, all FSJ's came with a Low-range.

<BLOCKQUOTE>quote:</font><HR>5. Any other info that may help me better understand the various systems, their operation and their limitations.<HR></BLOCKQUOTE>

There are two basic modes for 4wd systems, Part-time or Full-time:

* Part-time mode locks both front and rear driveshafts to spin together. This system can only be used on loose-traction surfaces (snow, dirt, gravel, etc) that allows one of the wheels to slip, as they each travel through different arcs (and thus rotate different amounts) in corners. Page 104 of the February _Four Wheeler_ has a good illustration of this.

* Full-time mode employs a differential between the front and rear driveshafts, which allows it to be used on high-traction, low-traction and mixed-traction surfaces. All full-time cases used in FSJ's (except the '86 NP228) employed a device to limit the amount of slippage between the front and rear driveshafts, so that at least two wheels will get some power. With the NP228, all power might get directed to one tire that loses traction.

* Low-range was a lower gear that multiplied torque-output in 4wd; although most cases employed it as a part-time mode, the Borg-Warner Quadratrac (BW QT) had a full-time low-range as well.

* All part-time cases, and some full-time cases, had a 2wd mode as well. While this was always a 1:1 drive ratio from the factory, BW QT cases with the Milemarker part-time conversion had a 2wd part-time Lo-range mode as well.

<BLOCKQUOTE>quote:</font><HR>I hope this is not the umpteenth time these questions have been asked but I did search the topics for a comprehensive listing but was unable to find one.

From what I have read I think staying away from the NP229 sounds like a good idea.<HR></BLOCKQUOTE>

I'm quite happy with mine; as long as it's well maintained (which is hard to verify in a used FSJ), it will last a long time (mine has gone 180,000 miles with nothing more than new output seals).

<BLOCKQUOTE>quote:</font><HR>I have read the Tech Article Section for the transfer case listings but don't understnd the difference between the NP-208, NP-219, NP-228, BW-1339.

I understand that the BW-1305 doesn't have low range but does the D20?<HR></BLOCKQUOTE>

Well, here's the rundown of what was available, the rough years of availability, and what modes each employed. (PT=Part-time, FT=Full-time)

D20 (1962-1979):
4HiPT, 4LoPT, 2Hi

D21 (1962-1965)
4HiPT, 2Hi

BW1305 Quadratrac (1973-1979)
4HiFT, 4HiPT

BW1339 Quadratrac w/optional Low-range (1973-1979)
4HiFT, 4LoFT, 4HiPT, 4LoPT

BW1339 Quadratrac w/part-time conversion
2Hi, 2Lo, 4HiPT, 4LoPT

NP208 Command-trac (1980-1987; up to 1988 and maybe even to 1991 for fleet and government orders)
4HiPT, 4LoPT, 2Hi

NP219 Quadratrac (1980-1982)
4HiFT, 4HiPT, 4LoPT

NP229 Selectrac (1983-1985, 1987-1991)
4HiFT, 4LoPT, 2Hi

NP228 Selectrac (1986)
4HiFT, 4LoPT, 2Hi

<BLOCKQUOTE>quote:</font><HR>I would like to do some 4-wheeling into the back country with the family and friends.

I know it's a huge question but the Engineer in me needs to know research the heck out of everything so I can make an informed decision.<HR></BLOCKQUOTE>

Any of the above cases will serve well for the kind of four-wheeling you describe. I like the extra traction that full-time 4wd give me in my QT and NP229-equipped trucks, and I don't miss the lack of a 2wd mode in my QT, since I keep the NP229 in 4wd most of the time anyway. Gas-savings in 2wd are negligible, if there are any at all.

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Bob Barry<UL TYPE=SQUARE>* '78 Cherokee 4-door
* '88 Grand Wagoneer[/list]http://studentweb.providence.edu/~rbarry/wheels/

[Coley]

Can we say...new addition to the Tech Section? Maybe name it "Everything you Wanted to know about FSJ 4wd Types, but Were Afraid to Ask" or The Rosetta Stone of FSj 4WD Systems"


Thanks again to the indomitable Dr. Barry.

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Daddy's Ice Cream Truck (3 yr old daugter named it)
360 727 NP229
Totally stock
"You're obsessed with that thing!"

[MonsterMash]

I totally agree with Coley!

I'm just wondering when the syllabus and work-book will be available.


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'84GW360--"Spinner"
Bigger tires and better stereo but pretty much stock
Most everything works some of the time!
1st Annual Jefferson FSJ Mud Run:

http://home.earthlink.net/~worthservices/index.html

[UnkleMunky]

Yea on the 4wd outline from Bob! Super well done! I agree it's worthy of keeping posted separately. ME...I'm nabbing the info and keeping it in a Treepad file(where I keep all my other handy dandy info like that) so it's at ready access whenever need be!

Ya'll might like to check this program out(free) and see if it comes in handy for storing tidbits of info in an organized form!

http://www.treepad.com

GREAT job and VERY much appreciated, Bob! Thanks!

Michael
'78 J10/'76 J10

[scotty]

agreed! a very informative response.im glad you got to it first,and saved me the typing

a couple of other comments on xfers and 4 wheelin:

-all but the d20 and d21 are aluminum cased,chain driven xfer cases.the d20 and d21 have a cast iron case,and use gears to connect the front and rear outputs. this IMO,makes fora more durable xfer for rigorous off road abuse.the d20 was only available with an auto until 72 or 73,after that it was only attached to a manual tranny and the BW QT was attached to the th400.there are many different arguments in favor of autos and manuals for wheelin.my personal preference is a manual,but i wont get into that here.

-the BW QTs biggest downfall is the fact that the chain constantly drives both outputs.newer cases with a "straight thru" design(the output directly behind the input) are quite a bit easier on the chain,since the chain only has to drive the front. for this reason the chain is twice as thick as any other aluminum case,and still only lasts half as long.it is reccomended to change the chain at 60,000 mph intervals. this in fact is one of the biggest reasons for QT failure,is the owner ignores the telltale popping and slapping of the chain jumping teeth on its sprockets.eventually it breaks and youre left with a little pile of aluminum xfer case rubble.i personally think that the fulltime 4lo is a neat feature.driveline bind on high traction surfaces such as rock,hardpack dirt,or pavement can be a prollem with a partime xfer locked in 4lo. a part time converted QT gives you rwdhi,rwdlo,4wdhigh(part time),and 4wdlo(part time). this is also a neat feature,and ironically just like an old spicer 18 xfer,except that you have a switch for 2wd/4wd instead of a lever.

-on the 228/229: the 228 is useless for just about everything.it uses a simple open center diff,and as a result,power can easily float to the axle assembly with the least traction.with open diffs in the axles,it is quite possible to get only one wheel spinning while in "4wd".the 229 at least uses a silicone filled viscuous coupling in its center diff to control fron/rear slippage,and when its working correctly,this setup actually works very well.for some reason,it does seem to be a more common prollem for the 228/229 to crack case halves,definately moreso than any other case,including the full time np 219 and the BW QT.

tho in all fairness,prolly alot of 229 failure is prolly due to owner neglect and lack of maintenance. the 228/229 use a problematic vaccum motor to move the mode lever back ond forth,and if the case has hardly(or never) been shifted,these levers tend to "freeze" up and need to be worked with to function normally again.in an "inclimate weather" rig that is mostly street driven,and only mildy wheeled, the full time 4hi on the 229 is a nice feature,as you can put it in 4wd in november and leave it there until march,if you want to,without having to worry about whether the road surfaces is slippery enuff to use 4wd without driveline bind.

if you want a rig you can really beat on off road often i woulndt use a 228/229 for one simple reason: if you have trouble with a rear driveline(broken axle,u joint,whatever) you cannot drive home in full time 4hi on only the front shaft.damage to the V/C will result. the np 219 and the BW QT both have a lockable high range,so that you can limp home on the front if you have to. with a 229/228 you can only drive on the front if you get there in part time 4lo.this may seem like an unlikely situation,but ive had to do it more than once.

as you can see,it depends alot on how you intend to use it. hopefully Dr Barrys info,alog with this,will give you some idea what system will best suit your needs.

you can have more fun than you ever thot possible with a well set up and maintaned 4wd vehicle.

let us know if you have any other questions...

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scott
85 grand wagoneer
258 with motorcraft 2bbl/904/twin stick dana 300/dana 44/welded amc 20
38x15.5 gumbo mudders
snorkel/dual batteries/onboard air/"custom" convertable
3 inch body lift/mostly stock suspension/"modified" fender openings
custom front/rear bumpers and brushgaurd

T18/dana-spicer 18 with drum E brake and PTO swap very soon
searching for offset QT rear and PTO winch

[Rob]

Lots of info..very impressive.
Thanks Mr. Barry. Sure something to save.

One Q though, about the Q-Trac without lowrange. You consider this FT or PT? Or do you mean the E-drive to be FT?

[bignblue]

Nope, the QT is ALWAYS full-time 4wd. The E-drive locks the front and rear outputs together for a true four wheel drive. In unlocked operation, the QT doesn't split power 50-50 between the front and rear shafts--it's more 60-40 biased towards the rear (or so I've heard--standard disclaimer). Because the outputs are locked, E-drive can't be used on the road b/c there's no slippage which is needed to prevent binding.

If you have the Milemarker PT kit installed, you lose the E-drive function. Instead, the E-drive switch is used to transfer between normal QT operation and 2wd. The low range lever still works, so you have the offset benefit of a 2wd--but I don't know how that would be useful except for towing.

Scotty, I want to service the 229 in my new Waggie (as soon as it gets warm). So far I'm just planning on changing the lube--what else do you suggest?

[desert_freak]

Thank you all, especially Bob Barry and Scotty. I am so glad I posted the question, and evidently so are a few other people. This is exactly the kind of information I was hoping to get. I tend to overanalyze everything and wanted to have a better understanding of all the systems so that I felt as though I was buying the best system for my or at least not the wrong system for my needs.

Bob already answered my followup question about mpg savings with a system able to operate in 2wd. If the saving are negligible then I won't focus on a system that has this feature. I'm a firm believer in preventative maintenance and a big fan of overkill, so I suspect I could maintain any of the systems. But I'm sure after I study the systems a little more one system will stand out in my mind.

Thanks so much everyone.



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[scotty]

rob,the qt is a part time case,but with the E drive on is more or less in "part time mode" sice the front and rear shafts are mechanilally locked together,and E drive is not for use on pavement. as bignblue stated,a part time converted QT no longer has fulltime 4wd,or the e drive function. now the e drive switch is the 2wd/4wd selector. wether the QT has a low range or not is not important,since low range is useable in fulltime 4wd(2wd in a p/t converted) or in e drive(4wd in a p/t converted).

i seem to remember a thread a couple months ago debating full time/part time bth in terms of xfer case operation,and terminology in jeep manuals.i hope you havent started that ball rolling again here

as for the 229,if its working properly now,id simply replace any leaking seals,run the vent up high,and check it after every outing. if the atf looks like pepto bismol,change it. hopefully if you keep it full of clean fluid,the only trouble youll have is the vaccum thingy,and hopefully youll never break somethin n the rear and have to drive home in 4lo


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scott
85 grand wagoneer
258 with motorcraft 2bbl/904/twin stick dana 300/dana 44/welded amc 20
38x15.5 gumbo mudders
snorkel/dual batteries/onboard air/"custom" convertable
3 inch body lift/mostly stock suspension/"modified" fender openings
custom front/rear bumpers and brushgaurd

T18/dana-spicer 18 with drum E brake and PTO swap very soon
searching for offset QT rear and PTO winch

[BobBarry]

<BLOCKQUOTE>quote:</font><HR>Originally posted by bignblue:
Nope, the QT is ALWAYS full-time 4wd. The E-drive locks the front and rear outputs together for a true four wheel drive.
[snip]
If you have the Milemarker PT kit installed, you lose the E-drive function. Instead, the E-drive switch is used to transfer between normal QT operation and 2wd.<HR></BLOCKQUOTE>

Heh... I am NOT going to revisit the full-time vs. part-time definition debate (if you want my opinion on that, you can search the archives on that one; that thread went on for two pages, totalling over 100kb, with references, footnotes, 8x10 glossy photos...)

Back to the Milemarker kit; all it does is convert the BW QT's full-time 4wd mode to a 2wd mode. The part-time 4wd mode (Jeep's "Emergency-Drive") is left untouched, and thus becomes the only 4wd mode the case offers. That's why I prefer to think of that kit as a "Full-time 4wd Eliminator" kit, since is uses the part-time mode that the case already had from the factory.

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Bob Barry<UL TYPE=SQUARE>* '78 Cherokee 4-door
* '88 Grand Wagoneer[/list]http://studentweb.providence.edu/~rbarry/wheels/

[Gladi8r]

<BLOCKQUOTE>quote:</font><HR>Originally posted by UnkleMunky:
Yea on the 4wd outline from Bob! Super well done! I agree it's worthy of keeping posted separately. ME...I'm nabbing the info and keeping it in a Treepad file(where I keep all my other handy dandy info like that) so it's at ready access whenever need be!

Ya'll might like to check this program out(free) and see if it comes in handy for storing tidbits of info in an organized form!

http://www.treepad.com

GREAT job and VERY much appreciated, Bob! Thanks!

Michael
'78 J10/'76 J10<HR></BLOCKQUOTE>

Michael, I took your advise and checked out the TreePad.com site and I really like this program, only thing is, I couldn't get the PIM template to download from the utilities section. Great program though. I can now use it to store all the info that I have been hoarding from this forum



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DON

1988 GW mostly stock, &lt;---Wifey's truck (won't let me "fix it up")

1971 J-4000,Rhino Grille(to be installed)
360 CID 8.5/1 ratio 2v, 245 HP, 365 ft/lb
T-18A, Dana 20, PTO, DANA 44 (Front/Rear)
Soon to be torn down for Resto
71 Gladiator Pics

78 GW (parts truck)
360 4v Th400
Dana 44 F/R

http://www.j-trucks.freeservers.com/

78 Wagoneer Pics

[Rob]

Sorry guys, I didn't intent to open a can of worms. I must have missed that thread; it was prolly before I joined the club.

I was just confused to see the Q-trac listed both as FT and PT. I thought I could only be one of the two. Now I understand BB did it on purpose to avoid the discussion.

FT or PT, never mind, I would be very happy if I would just get the rig driving again!

Thanks for your answers.