Anyone HAPPY with Borg Warner 44-44 / Auto 4WD

[WilliamS]

I emailed Sean at Hemifever and he does not have transfer case access. That would've been great if he could have tuned it to have the clutch stay engaged while in 4Lock and 4Low

Crap, so I want the only one to think of it. So an over ride.

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[muddy12]

Unless I'm reading it wrong, the way it's described in post #253, the electronic part of it is already "energized" when in 4lock and 4 lo.
That means that when in 4 lock and 4lo, the slippage is coming from the ball ramp and spring. It doesn't appear to be any way to "electronically" lock the front and rear.



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[WilliamS]

Unless I'm reading it wrong, the way it's described in post #253, the electronic part of it is already "energized" when in 4lock and 4 lo.
That means that when in 4 lock and 4lo, the slippage is coming from the ball ramp and spring. It doesn't appear to be any way to "electronically" lock the front and rear.



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Something to tell the ramp to be at full friction on the clutch. There has to be a way.

 

[Jared4.7]

Im looking at a truck that has the auto t-case in it. Im not a rock crawler, not a mudder. Is it that bad for a city guy like myself that might see a little snow now and then?

 

[Hemi395]

Im looking at a truck that has the auto t-case in it. Im not a rock crawler, not a mudder. Is it that bad for a city guy like myself that might see a little snow now and then?

A little snow now and then you should be ok. But there have been several guys on here that burned up this tcase getting unstuck from deep snow. Personally I've never had that problem but I can't say I'm not nervous driving my truck through deep snow...

 

[Hemi395]

Something to tell the ramp to be at full friction on the clutch. There has to be a way.

The major flaw with this tcase is when the throttle is let off there is 0 pressure on the clutch in ANY 4wd mode. This could be fixed with programming. It wouldn't be a true locking tcase but better than it is...

 

[WilliamS]

Well it's only recently that they figured out how to unlock the transmission I assume it's only a matter of time till they can get into the transfer case and fix this issue. although for me it is not an issue it would be a nice thing to have an actual locking differential in 4hi and 4lo

 

[Hemi395]

I agree. The 4Auto is nice in heavy rain and light snow but the option to lock should be there

 

[iam_canadian22]

Unless I'm reading it wrong, the way it's described in post #253, the electronic part of it is already "energized" when in 4lock and 4 lo.
That means that when in 4 lock and 4lo, the slippage is coming from the ball ramp and spring. It doesn't appear to be any way to "electronically" lock the front and rear.



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It was brought up a while back that directly from borg warner these cases lock in 4lock-4low. The issue is in the programming on ram's side. This t-case comes in other trucks and works normal.

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[Murphy Slaw]

This t-case comes in other trucks and works normal.

What other trucks use the 44-44 ?

 

[Hemi395]

I believe the higher end F150s and Tundra's​...

 

[muddy12]

It was brought up a while back that directly from borg warner these cases lock in 4lock-4low. The issue is in the programming on ram's side. This t-case comes in other trucks and works normal.

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I have no doubt that these cases lock, I just question the method by which they achieve that "lock".

I was finally able to find a borg warner video about the operation of their torque on demand cases (pretty sure the 44-44 falls into this group).
Is showed all the same parts as we're mentioned in the earlier post(electromagnetic, and ball ramp, etc).


The video made it appear that the only part that applies pressure to the clutch pack, is the ball ramp mechanism. Ball ramps, by design, require a little slippage to make them open.
The video also made it seem as if the electromagnetic part(part that is controlled by programming) only "locks out" the ball ramp.
Example:
2wd, ball ramp locked out, no power to front.
Auto4x4, ball ramp lockout controlled by computer, and allowed to function only when rear wheel slip is detected.
4lock, ball ramp unlocked, and engagement controlled by torque applied.


Honestly though, I hope I misunderstood how it works. I'd love to be able to "reprogram" it, or simply add a "lockup switch".


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[muddy12]

After watching the video several more times, I think I had the electromagnetic part backwards. It seems that the ball ramp is held in the disengaged position by spring pressure, and the electromagnet pushes the ball ramp into/against the clutch pack. However, it only applies enough force for about 20% torque to be sent to the front. It then requires a little bit of a speed difference(between the front and rear shafts) to actuate the ball ramp, and apply full locking force to the clutch pack.


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[Hemi395]

Honestly though, I hope I misunderstood how it works. I'd love to be able to "reprogram" it, or simply add a "lockup switch".

Someone awhile back was looking into wiring a lockup switch but then traded in his truck for a 2500. I don't think he got very far into it except figuring out which wire to tap into. I just don't have the electrical knowledge to attempt this and I'd be afraid of frying something. I do know most everything in a vehicle runs either on 5V or 12V. Sending 5V to something that runs on 12V won't hurt much but sending​ 12V to something that runs on 5V has the potential to fry things.

I would love to be able to flip a switch that would force the clutch to be engaged. Since it's a lot harder to overcome static friction, it should function almost like the 44-45. Honestly I probably wouldn't use it except for certain situations like deep snow or soft sand. But it would be nice to have.

 

[Ken226]

Muddy, your understanding matches my observations. If you get stuck first, in a forward gear, then after stuck you shift into 4 lock, the rear wheels will need to rotate about 180°max before the front wheels can engage.

Similarly, many traditional 4x4 systems may require the same, in order for the forks to move dogs into place, meshing gears.

If already in four lock before getting stuck, as long as the front wheels are tracking over the road at the same speed as the rear wheels, the ball ramp will not be applying torque to the front wheels. If the front wheels begin tracking over the road at s higher speed than the rear wheels, such as while turning, the ball ramp will allow the clutch to slip.

Only when the rear wheels try exceed the front wheel speed does the ball ramp apply an axial force to the splined clutch basket closing the clutch plates. Given the surface area of the clutch plates and the mechanical advantage of the balls/ramps, the clutch should be transferring about 1200-1400 ft lbs to the front before any slipping or breakage of the clutch. With a 3:1 ish first gear ratio, it can likely transfer all the hemis torque without slipping. Remember, that the more torque the engine applies to the ball ramp, the more the clutch plates are compressed. The ball ramp has two possible states. It is either (unpowered/off/not allowed to engage) or it is (powered/on/allowed to engage). When it's powered, it will require somewhere between 0° and 180° of ∆< (change in angle) between the rear and front drive shaft.

I'm not sure how it works in reverse, I dont recall seeing any double Bi-directional ramps. Unless it has them, it would be relying on torsion spring alone for the axial clutch pack load in reverse and would really really suck.

But, while not ideal, based on observations of the guts of this case, if your in 4 lock ahead of time when you encounter slippery conditions,. The ball ramp will allow somewhere between 0° and 180° of ∆ < between front/rear wheels. Once the rear wheels slip.


So, to reiterate, unless I made a serious error in my observations, there is no electronic control of the clutch plates clamping force (for lack of a better term). The computer controls the ball ramp only, the ball ramp forces the clutch plates together.

In 4 auto, the computer sends power to the ball ramp when the wheels peed sensors detect slippage. It the shuts off power when the wheel speeds all match.

In 4 lock, there is continuous power to the ball ramp. Slip or no slip, constant power. I don't recall if the ball ramp is powered at tps -0- or if the throttle position must be a positive value first.

If your in 4 lock, applying power, the ball ramp will apply all of the engines torque through to the front wheels. This should occur before the rear wheels have rotated 180°.

The thing I haven't figure out yet is reverse. Think of the ball ramp as being like a ratchet, then spinning the ratchet handle backwards, it doesn't apply torque to the socket unless you change a setting. I don't recall seeing the mechanism that allows this.

It must have it though, otherwise the front wheels couldn't do anything in reverse. If the ball ramp is bi-directional, it would have another obvious downside. If all 4 wheels were spinning while trying to go forward, then you shift into reverse, the rear wheels will have to spin a few turns before the front wheels are engaged. Then the same again, when you shift back into drive.

Looks like that's the price to be paid for a 4x4 that doesn't bind in turns.

 

[muddy12]

Ken, that 180degrees is what was giving me problems over the weekend. I was in 4lo, and backing a trailer next to my house. That little bit of slip before the front engaged, was enough for the back end to start to slide sideways, which made the trailer turn towards the side of the house.


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[Ken226]

I agree, it's certainly not optimal. In my own case, I was attempting to back a trailered boat across a soft grassy area, in a narrow rectangular space.

There was a set of 8" deep pre-existing ruts and I was trying very hard to keep both my wheels OUT of the ruts, as there were deep and muddy.

The space was just wide enough that I could back the trailer with mine and the trailers wheels about a foot away from the ruts, paralleling them, on one side.

I was in 4 lock, ahead of time. All was well untill the rear wheels started spinning with no front wheel help. The rear wheels slid laterally and dropped into the ruts. Afterwards, of course, the fronts engaged and started digging themselves in too.

I had to disconnect the trailer right there.

At that point, in going forward, the rears spinning first was a moot point. The tires (Atturo Trail Blade 33-12.50r20s) we're coated with a ton of thick mud. It took alot of Fc=mv^2/r to get out.

Pure speed and centrifugal force to sling the mud out of the knobs got it moving forward and out.


So, perhaps funny to any uninvolved third party, but certainly not to me, was the hundred pounds of mud on the front of my boat.

So far, the transfer case is irritating. No property damage or loss of life or limb, but certainly can be irritating. I won't trade it in over this, but when the time comes I'll know better next time.

 

[muddy12]

"Irritating........won't trade over this....."
That's pretty much how I feel about it as well.
Just wish I had known about it before I bought. I was looking at two almost identical trucks, the 1500 I bought, and a 2500. At the time, I couldn't justify the extra cost for the 2500. Had I known about the t-case, I probably would have purchased the 2500 instead.


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[loveracing1988]

Muddy, your understanding matches my observations. If you get stuck first, in a forward gear, then after stuck you shift into 4 lock, the rear wheels will need to rotate about 180°max before the front wheels can engage.

Similarly, many traditional 4x4 systems may require the same, in order for the forks to move dogs into place, meshing gears.

If already in four lock before getting stuck, as long as the front wheels are tracking over the road at the same speed as the rear wheels, the ball ramp will not be applying torque to the front wheels. If the front wheels begin tracking over the road at s higher speed than the rear wheels, such as while turning, the ball ramp will allow the clutch to slip.

Only when the rear wheels try exceed the front wheel speed does the ball ramp apply an axial force to the splined clutch basket closing the clutch plates. Given the surface area of the clutch plates and the mechanical advantage of the balls/ramps, the clutch should be transferring about 1200-1400 ft lbs to the front before any slipping or breakage of the clutch. With a 3:1 ish first gear ratio, it can likely transfer all the hemis torque without slipping. Remember, that the more torque the engine applies to the ball ramp, the more the clutch plates are compressed. The ball ramp has two possible states. It is either (unpowered/off/not allowed to engage) or it is (powered/on/allowed to engage). When it's powered, it will require somewhere between 0° and 180° of ∆< (change in angle) between the rear and front drive shaft.

I'm not sure how it works in reverse, I dont recall seeing any double Bi-directional ramps. Unless it has them, it would be relying on torsion spring alone for the axial clutch pack load in reverse and would really really suck.

But, while not ideal, based on observations of the guts of this case, if your in 4 lock ahead of time when you encounter slippery conditions,. The ball ramp will allow somewhere between 0° and 180° of ∆ < between front/rear wheels. Once the rear wheels slip.


So, to reiterate, unless I made a serious error in my observations, there is no electronic control of the clutch plates clamping force (for lack of a better term). The computer controls the ball ramp only, the ball ramp forces the clutch plates together.

In 4 auto, the computer sends power to the ball ramp when the wheels peed sensors detect slippage. It the shuts off power when the wheel speeds all match.

In 4 lock, there is continuous power to the ball ramp. Slip or no slip, constant power. I don't recall if the ball ramp is powered at tps -0- or if the throttle position must be a positive value first.

If your in 4 lock, applying power, the ball ramp will apply all of the engines torque through to the front wheels. This should occur before the rear wheels have rotated 180°.

The thing I haven't figure out yet is reverse. Think of the ball ramp as being like a ratchet, then spinning the ratchet handle backwards, it doesn't apply torque to the socket unless you change a setting. I don't recall seeing the mechanism that allows this.

It must have it though, otherwise the front wheels couldn't do anything in reverse. If the ball ramp is bi-directional, it would have another obvious downside. If all 4 wheels were spinning while trying to go forward, then you shift into reverse, the rear wheels will have to spin a few turns before the front wheels are engaged. Then the same again, when you shift back into drive.

Looks like that's the price to be paid for a 4x4 that doesn't bind in turns.

The issue pops up when turning. When the wheel is turned it decreases clutch pressure per ram, idk if it messes with that ball ramp or not, but it happens. When it does that and you are actually needing 4wd it does slip the clutch and overheat it.

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[Ken226]

As a Mechanical Engineering student, studying this unit and figuring out how it works is an opportunity.

I've had alot more time to mull over the function of the bw44-44 and there are a couple of parts who's specs would be critical to the way the front wheels engage.

First, there's no electronic mechanism for releasing the clutch. The computer can't command the clutch release. There's no way for the computer to accomplish this as the electromagnetic portion of the clutch is unidirectional and can only begin the lockup process. After the electromagnetic clutch begins the lockup process, it's dependant on engine torque to remain engaged.

Releasing of the clutch is accomplished mechanically by a spring, and will occur automatically when the torque value applied to the ball ramp falls below the torsional force (opposite direction) applied by the torsion spring. Or, any time the front wheels/driveshaft advance (relative rotation, as in relative angular translation, relative to the rear wheels).

Imagine the front and rear drive shafts rotating together, at the same speed. Holding the same clock position relative to each other. If the rear driveshaft tries to rotate faster, it accelerates the front driveshaft with it, keeping the same angular velocity. However, if the front driveshaft tries to increase it's angular velocity beyond that of the rear driveshaft, it is allowed to do so. In doing so, it's clock position relative to the rear driveshaft advances and the torsion spring/ball ramp immediately uncouples the system.

If the clutch is releasing, causing disengagement of the front wheels while under power, then there are several possible causes. 1. The torsion spring is overly strong, causing the ball ramp to disengage at a lower torque value that intended. 2. The ball ramp is damaged in a manner that results in the torsional force not being properly converted to axial force, or 3. The the clutch pack is worn/damaged and slips despite the axial load from the ball ramp.

It seems that the most critical attribute determining the systems engagement properties is the ratio of electromagnetic clutch force to torsion spring force/rate.

Perhaps a weakness of the design, but, If the electromagnetic clutch's plates were to become worn to the extent that they can no longer hold with enough force to allow the engine torque to overcome the torsion spring and begin applying the correct axial force into the clutch pack, the electromagnetic mechanism would not have nearly enough clamping force to transfer all the engine torque through the front wheels.

Here's a theory that may explain why your front wheels could be releasing when you turn your wheels. Its very difficult to be articulate enough to explain something so complex, so bear with me.
Tell me what you think:

Assuming your in a low mu surface, very low coefficient of friction, in 4 lock and applying throttle causing all 4 wheels to rotate.

If your clutch pack is very worn, and the electromagnetic mechanism cannot apply enough drag to hold the drum and allow the engine torque, through the ball ramp, to overcome the torsion spring and apply the full axial load through the clutch pack, but due to the low mu surface of the road, the electromagnetic mechanism is (just) providing enough clutch holding force to allow the front wheels to rotate.

However, when you begin turning your steering wheel, the change in the front wheels angle, within the ruts they are sitting in, causes a rapid increase in the coefficient of friction with the road , plus the increased angle of the wheels/axles takes more force to rotate, and the engine torque immediately overcomes the electromagnetic clutches holding force.

Is this possible/probable based on your observations?

The most obvious and serious consequence if that is the previous is the case with your truck, that in any low mu surface using 4wd, your clutch would be continuously slipping and further destroying itself.

The engineers who designed this thing obviously intended to reduce the electrical power needed to pass torque through the clutch pack, by using a wimpy little electromagnetic mechanism to start the process, a rotating ball ramp mechanism to provide the actual clamping force to the clutch plates, and a very powerful torsion spring to force disengagement once the torque load between the drive/driven portions of the clutch pack drops below a certain value.

To work properly, it would be very dependant on the condition of the clutch plates and torsion spring. Once the clutch plates become appreciably worn beyond the point that the electromagnetic mechanisms engagement with them can produce sufficient drag to allow the engine torque to overcome the torsion spring, there would be a rapid cascading failure as the lack of ball ramp load would allow continuous clutch slipping under load.

A significantly weaker torsion spring might allow the ball ramp to engage much more positively and stay engaged untill the torque Differential in the clutch is nearer zero.

I'd try it, but mine actually works very well and exhibits none of the aforementioned problems. I don't wanna fix mine untill it breaks.

Anyone wanna donate a bw44-44 for experimentation purposes��. Joking of course.