4A transfer case does it have a mechanical lock in 4H

[ssls6]

I was watching a bronco video and the author said the transfer case in the bronco with 4A has a real mechanical lock when in 4H. I thought the bronco had a BW 44-44 which in prior versions only used the clutch plates fully engaged when in 4H...no mechanical lock. Does anyone know if the author was correct? I would love to think that 4H has a real mechanical lock. I live in snow country so 4H is used a lot when the roads are snow packed.

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[Roger123]

Interesting, I never even thought about it, I just assumed it was "locked" in 4H and not using "locked up" clutches.

 

[HertiageMerica]

https://www.bronco6g.com/forum/threads/transfer-case-technical-discussion.52097/post-1555290

 

[RagnarKon]

It uses clutch packs, which are mechanical, yes. Those clutch packs are electronically driven.

If you are asking if it uses a physical gear to engage 4x4. No, it does not.

 

[BigMeatsBronco]

this is good news for the rest of the drivetrain as well... I have hundreds of thousands of miles of seat time with these clutch driven engagement Borg Warner transfer cases (in other vehicles) and I prefer them greatly over the older style with mechanical lock. I've never had one fail or become so loose that it slips in low range. I've disassembled them and understand the concept of how they work with the ball ramps against the flat plate with grooves and have determined that is one of the best designs available to transfer large amounts of torque consistently and effectively. And just like any other wet clutch it offers a slight protection for the rest of the drivetrain under huge shock loads it could reduce the shock to the rest of the drivetrain by slipping ever so slightly.

additionally Ford used this same design in the first pro4 race trucks 20 yrs ago because they are tough and reliable.

 

[Oilbrnr]

So in 4A it is either engaged then fully when wheel slip via ABS is detected, or 2HI otherwise correct? There is no partial engagement letting the clutches slip to vary output F/R? (and the front driveshaft is always spinning, ie no front axle disconnect?)

 

[RagnarKon]

So in 4A it is either engaged then fully when wheel slip via ABS is detected, or 2HI otherwise correct? There is no partial engagement letting the clutches slip to vary output F/R?

By the nature of being a clutch pack, it does allow it to have partial engagement for brief periods of time. But it's not like it's going to sit in the partially engaged state, that would burn up the clutch pack.

(and the front driveshaft is always spinning, ie no front axle disconnect?)

Yeah. Well... I guess it depends on what the gears are doing inside the differential. But something on the front-end is always spinning.

 

[ssls6]

Ram used the BW44-44 and had issues with people using their transfer case in 4H or 4L, high speed usage, high torque conditions led to high heat and failed clutch packs. BW responded with a BW44-45 which had dogs and clutch plates (the engagement dogs were at least in 4L, I'm not sure about 4H). I'm just not sure what transfer case BW supplies for the bronco.

I'm not saying the 44-44 is bad, it's just needs some care so you don't over heat it. It does modulate the pressure on the plates when wheel slip is detected. In locked mode, it applies full pressure.

 

[crenca]

So in 4A it is either engaged then fully when wheel slip via ABS is detected, or 2HI otherwise correct? There is no partial engagement letting the clutches slip to vary output F/R? (and the front driveshaft is always spinning, ie no front axle disconnect?)

To add to what @RagnarKon said, in 4A it's not really about wheel slippage detected by ABS. The system is actually more old-fashioned than that, it's based on an algorithm that looks at throttle, gear selection, steering angle, and throttle position. It applies torque to the front axle most of the time in the lower gears, really only backing off at extreme steering angles. In other words, it applies it without any input from wheel slippage, the weather, traction conditions etc. - so it's applying torque to the front axle in the same way, whether you're on dry pavement, or snow or mud or whatever.

And yes, your front axle and differential are always spinning whether you have it in 2H, 4A, and of course 4H and 4L

Also, as already mentioned, it is the only method that the front axles are engaged, no matter what you're in, including 4L. Yes, it is "locked" mechanically, and is a robust system that can handle the torque multiplication of 4L

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