Very Confused About Transfer Cases

[DavidNJ]

Hadn't given this a second thought. Don't all pickups have part-time transfer cases with dog gears, synchros, and shift levers that engage the front axle locked to the rear and optionally engage a planetary gearset for additional gear reduction? Apparently not!

Researching this has been difficult with lots of different technologies, minimal stuff easily found on the Internet and lots of somewhat conflicting stories. On top of that, there have been changes in the ownership of the transfer case manufacturers.

Let's stay with the BorgWarner cases on the DS and DT Ram 1500s, the 44-44/44-45, and 48-11/48-12. The 48-13 is a version on the TRX.

BW uses a chain to connect the input shaft to the front output shaft. This is common and BW uses the chain to distribute oil throughout the transfer case.

I always thought the part-time transfer cases used dog gears to engage the front axle. It is either mechanically locked or not.

BW uses a multi-disc clutch back to engage 4wd. I'm still trying to get a handle on this as it seems very similar to the Haldex AWD drive used on VW and some Audi models. Haldex is also owned by BW however I believe BW was using a multi-disc wet clutch before they bought Haldex. The discs in the video are hydraulically engaged as shown around 2:10 in the video below although I believe the Ram versions are all electromagnetic. the plate applying the pressure having ramps on 3 balls that press the disks together as the plate rotates.

This is a video of the BW box from a 4WD perspective:

However, it gets more interesting. This video shows a ram with a BW 48-11 in various settings. Note that the system is always starting open, even in 4Hi and 4Lo, and then decides to lock or come close to locking. This can be an issue in some situations where the driver relies on everything being locked for control. This would be most apparent where the driver is moving slowly with minimal and varying throttle. In the video below it is always on a relatively firm surface with a significant throttle application.

That video should be showing the 48-11 which like the 44-44 has the variable pressure on clutch engagement. There was a kit for the 44-44 to cause it to lock and not do the partially locked dance. There are reports of people using their trucks for snow plowing or use on the beach or other sandy surfaces who had failures with the 44-44 and some who converted to a 44-45. Haven't found any posts on the 48-11/12.

Snow plowing = BW 44-44 transfer-case failures - Transmission Digest

Experience we gain from solving problems generated in the transmission repair industry sheds light on various common failures and allows us to see trends that provide new products to solve design issues. From 2011 on, Dodge has offered Ram 1500 pickup trucks equipped with the BW 44-44 transfer...

www.transmissiondigest.com

Then apparently one of the configurations for the 44-44 and presumably the 48-11 is the tire size. From the documentation, I read the only sizes available are OEM and can't be changed other than to another OEM size. People are changing tire sizes all the time, so is that setting useless?

The mechanism is apparently also very sensitive to differences in tire diameter and a 1/4" difference in circumference. That could occur from mismatched tire pressures, a different size tire (must the spare be used only in 2Hi?), or even different tire wear (1/4" in circumferences is only 1mm, less than 1.5/32nds of an inch, in treadwear).

Transfer Cases and Tires: How RAM is changing the rules - Transmission Digest

Looking at the BorgWarner 44-44 and 44-45 transfer cases, we see an evolutionary change that started with the BW4405 and 4411 and has now reached this level of development. The design uses a wet-clutch pack in the transfer case to split torque between the rear and front axles.

www.transmissiondigest.com

BorgWarner 44-44 Transfer Case from the Electronic Side - Transmission Digest

Discover the inner workings of the BW 44-44 transfer case and its electronically controlled active full-time operation in Ram pickups.

www.transmissiondigest.com

So...I'm confused. Is it really hyper-sensitive to differences in tire-loaded radius? Is it subject to high wear in uses where it has slippage under high load/low traction surfaces? Does it not really lock possibly causing issues in some circumstances?

BorgWarner has been making a version of these transfer cases for over 15 years so presumably, they know what they want. Do they?

Note the Jeep Wrangler uses a Magna (Magna bought New Venture which was a GM/Chrysler program for New Process) box for many of its applications with the auto mode that uses similar wet clutches but has different programming. Haven't seen a comparison of the two.

 

[DavidNJ]

Note: the 48-12 part-time box is only on the Tradesman and the Rebel. All other models have the 48-11 except the TRX which as the 48-13.

 

[TNRamGuy]

Watching, as this is already way out of my league

 

[c3k]

This could explain why it's so important to program your dynamic tire circumference into the truck when changing tire sizes. AlfaOBD is one way (among several) to update these values. (I've done it 3 times...no problems at all.)

 

[Wolverine]

Very cool! As my father once told me, the 3 biggest technological advances in the automobile since he was young (born in the twenties), were tires, brakes and transmissions! I think he was right!

 

[theblet]

Does the limited in that YouTube video have BLD?

very interesting read!

 

[Snekpete]

It is my understanding that the RAM 1500 employs two different transfer cases, one that uses clutch packs and one that doesn't. The one with clutch packs is for the Auto 4WD and the one without clutch packs is for the manual 4WD.

As an aside, I accidently drove my Rebel several miles on dry suburban roads while in 4WD High. I never even noticed, even while making sharp turns. My old F150 would've groaned and jerked and spun tires if I had done that.

 

[DavidNJ]

Does the limited in that YouTube video have BLD?

What is BLD?

 

[DavidNJ]

It is my understanding that the RAM 1500 employs two different transfer cases, one that uses clutch packs and one that doesn't. The one with clutch packs is for the Auto 4WD and the one without clutch packs is for the manual 4WD.

As an aside, I accidently drove my Rebel several miles on dry suburban roads while in 4WD High. I never even noticed, even while making sharp turns. My old F150 would've groaned and jerked and spun tires if I had done that.

As I understand it all of the BW 44 and 48 series transfer cases use clutches and the only difference is the electronics. It could very well be 48-12 "part-time" transfer case also waits until it sees slippage. That strategy would make sense if they thought running 4wd on pavement was a more likely abuse of the transfer case than plowing snow or trying to pull a trailer uphill in deep sand.

This would be an example of pulling a trailer uphill in deep sand:

 

[devildodge]

Does the limited in that YouTube video have BLD?

very interesting read!

Every RAM1500 truck since 2009 has it

 

[devildodge]

What is BLD?

Brake Locking Differential System

For us guys without the Powerwagon lockers...there is BLDS

So, found out about a neat standard system on our RAM trucks. BLDS...Brake lock differential system. I will let the professionals describe it (yes, I know the blog is for a Jeep but our RAMs have the same system) https://blog.fcanorthamerica.com/2008/02/11/jeep-brake-traction-control-explained/

hdrams.com

 

[devildodge]

Overheating the 4x4 system

Went out today to do some more exploring with my son. Was wet and muddy. Ended up getting a message on my dash that the 4wd system had overheated and that 4wd performance is reduced. In the video you can see that the truck basically keeps switching back and forth to 2wd mode at around the 3:18...

5thgenrams.com

 

[theblet]

Every RAM1500 truck since 2009 has it

I thought some have lockers and a chain driven transfer case.

 

[devildodge]

I thought some have lockers and a chain driven transfer case.

I was refering to his question about BLD

BLDS. Brake Locking Differential System.

The only RAM 1500 to Ever have a factory locker is this generation Rebel and ORG.

 

[LouNY]

The 44-44 and 48-11 that have the auto 4wd button have clutch packs in them,
the 44-45 and 48-12 that do NOT have the auto 4wd do NOT have a clutch pack.
The t-cases with an auto 4wd function use clutch packs and an electronic signal to engage the clutch pack.

Depending upon your needs the 44-44 could be almost worthless.
the newer 48-11 does seem to do a much better job.

The 44-45 and 48-12 when in 4 Hi Lock and 4Lo Lock are locked with equal power out to the front and rear axles,
and the out put shafts rotate at the same speed.

The 44-44 and 48-11 with the 4 auto have a clutch controlling the output to the front axle,
with a varying voltage signal these clutches will vary their "lockup" to the front axle.

I have had both and I was extremely disappointed in the 44-44's operation under very low traction conditions, ice and snow.
Under more favorable traction conditions mud and dirt it seemed to work well unless worked hard for a long time,
at which it would give error messages and quit working.

The 48-11 seems to be working much better and also has much better programing, in very low traction conditions it does not
seem to require rear wheel slipage to engage and seems to hold in park and during hill descents.

 

[LouNY]

Also that video of the RAM getting all twisted up on that paved curbing and lifting tires in the air is NOT demonstrating the transfer case,
it is demonstrating the brake activated traction control system.

 

[Sascwatch]

No clutches in my rebel transfer case, leave it in 4wd on dry pavement and you’ll be bucking and hoping all over the place on sharp turns. One time I must have accidentally hit the 4hi button before backing out of my driveway and the truck didn’t like it one bit..

I’ve been very careful to engage 4wd only when traction is low, being able to do it on the fly is really nice and I can swap between 2hi and 4hi as needed when the roads aren’t completely snow or ice covered.

 

[DavidNJ]

After some more time with the 44-45 parts diagram...yes...it has a mode shift fork and no clutches. Presumably the same as the 48-12.

On BLD, yes, that is clearly the brake limiting wheel spin. No limited slip or electrically locking diff.

Note: The snowplow prep package is available on the Big Horn with the 48-11 and on the Tradesman with the 48-12. Stellantis/Fiat-Chrysler/Mopar/whatever seems to think the 48-11 is ok for plowing or is that just a marketing oversight?

I would have thought this would be a problem on the Wrangler forums where the Wrangler now has an available 4wd auto mode with a Magna transfer case that uses a similar clutch pack. I would have thought 4Hi and 4Lo would have just produced a voltage that locked the clutch pack and not cared about slippage.

Does the 48-11 actually lock solidly in 4Hi and 4Lo and only use slippage in 4Auto? Or does it wait to engage 4wd in 4Hi and 4Lo?

 

[DavidNJ]

Note: the 48-13 has an auto mode and 650 lb-ft of torque with the same 4.71 first gear. Presumably, the ECM limits that to something closer to 500 lb-ft in 1st gear, still over 2300 lb-ft at the transfer case. If it wasn't limited that would be over 3000 lb-ft.

The Magna UtilMax cases used in the Wrangler are rated for 1600 nm (about 1200 lb-ft) or 3800 nm (about 2800 lb-ft) in regular/4xe models with the auto feature or in the 392 (auto feature standard). The Magna catalog page (https://www.magna.com/docs/default-...ds/4wd/product_storyboards_ds_4wd_ultimax.pdf) says they have a "locking function of the clutch ensures excellent traction in off-road driving maneuvers".

The higher torque rated transfer case also has 6 pinions on the planetary range reduction gearset vs. 3 on the others.

 

[c3k]

After some more time with the 44-45 parts diagram...yes...it has a mode shift fork and no clutches. Presumably the same as the 48-12.

On BLD, yes, that is clearly the brake limiting wheel spin. No limited slip or electrically locking diff.

Note: The snowplow prep package is available on the Big Horn with the 48-11 and on the Tradesman with the 48-12. Stellantis/Fiat-Chrysler/Mopar/whatever seems to think the 48-11 is ok for plowing or is that just a marketing oversight?

I would have thought this would be a problem on the Wrangler forums where the Wrangler now has an available 4wd auto mode with a Magna transfer case that uses a similar clutch pack. I would have thought 4Hi and 4Lo would have just produced a voltage that locked the clutch pack and not cared about slippage.

Does the 48-11 actually lock solidly in 4Hi and 4Lo and only use slippage in 4Auto? Or does it wait to engage 4wd in 4Hi and 4Lo?

Note: the 48-13 has an auto mode and 650 lb-ft of torque with the same 4.71 first gear. Presumably, the ECM limits that to something closer to 500 lb-ft in 1st gear, still over 2300 lb-ft at the transfer case. If it wasn't limited that would be over 3000 lb-ft.

The Magna UtilMax cases used in the Wrangler are rated for 1600 nm (about 1200 lb-ft) or 3800 nm (about 2800 lb-ft) in regular/4xe models with the auto feature or in the 392 (auto feature standard). The Magna catalog page (https://www.magna.com/docs/default-...ds/4wd/product_storyboards_ds_4wd_ultimax.pdf) says they have a "locking function of the clutch ensures excellent traction in off-road driving maneuvers".

The higher torque rated transfer case also has 6 pinions on the planetary range reduction gearset vs. 3 on the others.

Great points. I searched pretty hard for information on BW 48-11 and -12 before I ordered. It's hard to get the kind of "how is it built", "how does it work" questions answered specificialy.