Can I pull the front DS in a V8?

[Big6ft6]

Joe

You definitly have a better understanding then me becuase my head is spinning . I can understand how having the front ds installed would prevent rolling down a hill, and how with it removed one would need to use the parking break. That I get.

But, to continue with your analogy using a standard rear axle, I don't see how if I held the drive shaft in my hand so it couldn't move and removed one side of the rear axle (we'll have to assume we're using independant rear suspension ) then spun the remaining rear wheel on the remaining rear axle, why would the output for axle I removed spin at a different rate? what would preven it from just spining freely in sink with the rear pinion. In order for there to be damage from slippage, it would need to be turning at a rate other than the otherside of the viscous coupler, I don't see what would make it do that?

But I probably shouldn't even be typing this becuase I have no idea what is under the trucks, I've never even looked under my explorer except to change the fuel filter, I just enjoy thinking about this mechanical stuff!
These kind of torque trasnfer systems have always baffled me on how they would work.

 

[gijoecam]

I don't have the details of the system in front of me, but the 4406 AWD transfer case uses a viscous coupling, not a mechanical or clutch type assembly. Nobody I've spoken to knows the details of how the unit works. I'd still like to contact someone at Borg-Warner on the matter.... All the info I have has been gleaned from either the OEM manuals or other members on here.

The only evidence I have to go by that it's not a direct drive to the rear wheels and, therefore, going to slip when driven, is the fact that many members on here have found out the hard way that when they remove the front shaft and park it on an incline, they return later to find that it has rolled. (IIRC, one member found his 100 feet down a long sloped driveway, slowly slipping towards a ditch) The only logical assumption that I can glean is that the parking pawl in the transmission locks the output from the transmission (same as the input to the transfer case) and, like a differential, if you try and drive both outputs in the same direction (i.e. both shafts in), it doesn't roll. If you remove one shaft, it rolls, and the missing shaft *should* turn the other direction. If it was allowed to turn in the same direction, park would never work even with both shafts in place.

Make sense?

 

[Big6ft6]

Make sense?

I agree it will roll when in park w/o front ds, completely understood. My original post was confusing becuase I said "if I understand correctly it doesn't slip in park" what I should've added is "what it does do is turn freely without the front ds to hold pinion, which is why it rolls down the hill" turning freely and slipping are two different things.

The viscous coupler allows the front and rear drive shafts to turn independant of one another when going around a corner etc on dry pavement and the outside steering wheel takes a longer path than the rear wheels, so you can't have the front and rear drive shafts locked, hence the viscous coupler that allows slippage between the two.

But with out the front driveshaft installed, there could never be a speed difference between the front and rear drivshaft, becuase there is no front driveshaft, so the coupler would never be slipping. But this is just theory in my head, I really don't know how it works, so don't make any decisions based on this.

Sorry, after reviewing my first thread I can see why, joe, you keep focusing on the rolling while park thing in your responses, my bad .

It would be neat to see a diagram of the whole thing.

 

[zfinger]

I dont understand all that techincal stuff, nor do I need to.

But the big "YES YOU CAN TAKE IT OUT" helps, thats what I needed to see. Going to get on that tomorrow and see how she does. I dont care about damaging the t-case as bad as that sounds, this truck is on its way out the door ASAP. And I bet she'll do some mean brakestands being 2wd!

 

[gijoecam]

...snip..."what it does do is turn freely without the front ds to hold pinion, which is why it rolls down the hill" turning freely and slipping are two different things.

I may not have been too clear either, and that may have helped confuse you... It does not 'slip' in the truest sense of the word, and it does not turn freely either. The VC allows *some* level of differentiation between the front and rear driveshafts. That we know. However, it's not an unlimited amount like an open differential. If the system used a center differential like the Land Rovers and Audis used to, then yes, the vehicle would roll freely when in park with the front DS out. The viscous coupling allows *some* limited amount of movement between the two shafts. That'a about all I know about the system, unfortunately.

The viscous coupler allows the front and rear drive shafts to turn independant of one another when going around a corner etc on dry pavement and the outside steering wheel takes a longer path than the rear wheels, so you can't have the front and rear drive shafts locked, hence the viscous coupler that allows slippage between the two.

part correct, and part incorrect. The VC does allow different driveshaft speeds, but only up to a certain amount (again, how much exactly, nobody is really sure). That difference is limited by the VC.

Here's another way to think about it: Change the term 'viscous coupling' to 'limited slip center differential'. That may just make things worse though...

But with out the front driveshaft installed, there could never be a speed difference between the front and rear drivshaft, becuase there is no front driveshaft, so the coupler would never be slipping.

Not true... your input torque gets transferred to the VC which then splits the torque between the front and rear outputs. Torque will always take the path of LEAST resistance first. That's why a wheel on ice spins before the wheel on pavement. Now, the VC limits the slippage (think Torsen or TruTrac) so that some portion of the torque gets sent to the high resistance output side (in the case of no front D/S, that would be the rear), but the VC is forced into slipping.

Sorry, after reviewing my first thread I can see why, joe, you keep focusing on the rolling while park thing in your responses, my bad .

It would be neat to see a diagram of the whole thing.

I think you're coming around.... Everyone's trying to learn on here.

Here's something else I'd like to try just to see what happens:

Can someone with a newly removed driveshaft on a AWD try this for us:
Mark the front and rear output shafts on the t-case with a paint pen. Then, with the vehicle in gear, have someone lay down next to the truck and watch the front output shaft. Have the driver step on the brakes, put it in gear, And while holding the brakes, give it a bit of gas. I suspect that nothing will move, or if it does, it'll be the front output moving very slowly. Now, while giving it a bit of gas, ease up on the brakes. Don't do a brake torque, but allow the vehicle to roll forward under power (i.e. driving it through the brakes) one wheel revolution. Then, look at the marks on the output shafts on the t-case. If the VC is slipping (which I suspect it will be), the marks should no longer be lined-up. If the VC is NOT slipping, the marks will STILL be lined-up (and my entire theory will be shot out of the water, and I'll happily eat crow ).

-Joe

 

[daffy]

Think of it like a rear axle turned-sideways. The input is the driveshaft, and your two outputs are the axles. Now, hold the driveshaft in place and put pressure on one wheel, and the other wheel tries to spin. If it cannot, the wheel you're applying torque to won't either. Now, break that opposing axle shaft, and there will be nothing to stop the wheel from turning.

I'm confused, what is holding the front wheels? They don't lock, save for being connected to the tranny with a park pin. remove that stop, and the truck would roll all day.

 

[gijoecam]

I'm confused, what is holding the front wheels? They don't lock, save for being connected to the tranny with a park pin. remove that stop, and the truck would roll all day.

The inability to turn the same direction as the rears. On an A4WD transfer case, that's not a problem as the parking pawl is solidly locked to the rear driveshaft. Not so with the AWD case. With the AWD case, the front and rear driveshafts are linked via the viscous coupling, not directly to the input shaft... make sense?

Think about it in terms of a differential again... When you put a 2wd truck in park, what holds the left side tire in place? The right side tire. Now, park it on an incline and jack up the left tire: The right tire is now free to roll because the left tire can now turn the opposite direction through the differential (and people can be injured, hence the reason they tell you to chock a wheel when jacking one wheel off the ground).


I'm not doing a very good job of describing this stuff, am I? I get the feeling I'm creating more confusion...

 

[Big6ft6]

Not true... your input torque gets transferred to the VC which then splits the torque between the front and rear outputs. Torque will always take the path of LEAST resistance first. That's why a wheel on ice spins before the wheel on pavement. Now, the VC limits the slippage (think Torsen or TruTrac) so that some portion of the torque gets sent to the high resistance output side (in the case of no front D/S, that would be the rear), but the VC is forced into slipping.

I see what your saying, I just can't picture in my head what a mechanism that could perform this task would look like. The whole concept of mechanically sending torque to the with MORE resistance (limited slpi) baffles me. Since I have not theory of my own, yours is as good as I got, but a mechanical device that does this just defies logic!

I think you're coming around.... Everyone's trying to learn on here.

Here's something else I'd like to try just to see what happens:

Then, look at the marks on the output shafts on the t-case. If the VC is slipping (which I suspect it will be), the marks should no longer be lined-up. If the VC is NOT slipping, the marks will STILL be lined-up (and my entire theory will be shot out of the water, and I'll happily eat crow ).

-Joe

Joe, now we're on the same page, I would like to see this done too. This will answer my question as well, simply mark the output for both front and rear drive shaft so they are lined up.

Then, with front drive shaft removed, drive around a bit, come back home and see if they are still lined up. I can't understand why they wouldn't be? What would keep the front from turning with the rear, there is no longer any resistnace from the front axle? But then again, I don't understand much : so I won't be surprised if they aren't line up, I'll just be confused

What if you removed both drive shafts and put in gear and ran the engine, then stopped, would marks be lined up then?

 

[gijoecam]

You're correct that there will be no resistance on teh front output, but there WILL be resistance on the rear output. Remember, it's driving against the weight of the vehicle. I guess *technically* it's the rear that will slip, but it's still slipping with respect to the front. If there was a way to see the input compared to both of them, that's what I'd really like to see.... mount the t-case on a dyno, where you can view the input as well as the output speeds, as well as vary the resisting torque to the front and rear outputs independently. Lord knows I'll never see something like that in my lifetime though....

-Joe

 

[Big6ft6]

So now I'm really thinking. How does a torque-transfer system know which axle isn't slipping and which one is? It has to be one of two things, it either senses speed difference, or load difference.

If it works on speed difference it would know if one drive shaft was spinning and one wasn't that the drive shaft that isn't spinning is the one with traction, and it should send torque to that drive shaft.

If it works on load, it would notice fery little load on the shaft that is slipping and larger load on the shaft with traction, and then send torque to shaft with larger load.

Now I'm going to move forward form here on the assumption that with both drive shafts removed both outputs rotate together, no slip in coupler. If this assumption is wrong, then you might as well stop reading, becuase the rest doesn't matter.

If it works on speed, then with front drive shaft removed, the truck would think that there is no slip, becuase both outputs would be moving together still just as if front drive shaft was installed and front wheels were moving rotating same speed as the rear. And in this case it front driveshaft should continue to move with the rear becuase coupler isn't sending anymore or less torque one way or the other.

Now if it operates on load, then coupler would definitly sense the front drive shaft has no load and assume that means it is slipping and send all the power to the rear wheels. I'm still not sure if this would do anyting to prevent the front drive shaft output from turning with the rear, but it is at least would make more sense.

So I guess I'm throwing this out for others to add to. Which is it a speed dependant operation, or a load dependant operation? I know with a normal rear axle differential it is based on speed, not load. But that sends all the power to the wheel that is slipping..so maybe this is different?

P.S. You know what would be really cool would be to sit in a room with some ford engineers while they are reading this thread and see how hard they laugh!

 

[X6StringerX]

P.S. You know what would be really cool would be to sit in a room with some ford engineers while they are reading this thread and see how hard they laugh!

I guess that would be payback for all of the times we've sat around and laughed at their engineering!

 

[Cleaverkid]

One more piece of advise, ZFinger. If you ever do replace that front DS, don't, repeat DON'T let anyone sell you a new DS that has U-joints at both ends instead of the original U-joint/CV joint setup. I made that mistake and after having the shop even replacing with a second 2-ujoint shaft, my truck vibrates like a banshee and I just get mad over and over.

Just my humble opinion.

Joe

 

[Turdle]

This is a good discussion. I will have to try Joe's experiment some day.

 

[X6StringerX]

I'll give the experiment a shot when I get around to removing the shaft.

 

[scottyfireman]

My Shaft Is Out...

I Will Try To See If I Can Get Time Tomorrow To Try It!!!

 

[gijoecam]

The BW-44-06 is torque-sensing. When all else fails, I defer to the shop manual:

The all-wheel drive (AWD) transfer case (7A195) is a two-piece aluminum, chain driven, viscous clutch type unit. This produces a system in which all-wheel drive is always activated. The all-wheel drive transfer case is automatic and has no external controls.

The viscous clutch is a non-repairable, torque distribution device. The internal construction of the viscous clutch consists of alternating plates that are connected to the front and rear outputs of the transfer case. The viscous clutch is filled with a high viscosity fluid which flows through slots in the plates. The resistance to shear causes the plates to transmit torque at the needed ratio. The ratio that torque is transmitted at is approximately 35% front and 65% rear.

A front differential compensates for the difference between the inner and outer wheels. However, when one driveline component travels farther than another, there will be driveline or torsional windup that must be released.


Operation

Torque is transmitted through the input shaft to the planet carrier assembly. Torque flow continues through the gear ring to the rear output shaft. Torque also flows from the planet carrier assembly to the sun gear shaft, which is splined to the drive sprocket. The drive gear is connected to the driven sprocket by the drive chain. Torque continues through the driven sprocket to the front output shaft flange. The viscous clutch provides the connection between the gear ring and the sun gear shaft.

I've got to stare at the picture to get a better grip on the power flow, but the power flows from the input to the VC, and the VC determines the torque split.

 

[zfinger]

I took the shaft out, and the noise went away. It runs and drives great too. She blows some mean donuts too! What else do you want for a $200 heap?

Problem solved

 

[reserved50]

im going to not reinstall my front shaft since its on backorder due to the cv boot exploding and get some 0-60 times before and after

 

[410Fortune]

I have 2 spare 5.0L AWD front and rear driveshafts....why not just fix the problem? I'll sell them for $80 + shipping each

 

[99SportX]

I myself have witnessed the front output on a AWD t-case moving slowly. I believe it was twitching and rotatiing very slowly while in drive and foot on the brakes keepong the vehicle stopped. This was on my friends X a while back, so I really don't remember exactly, but I did see it moving. This would indicate some slippage, but after installing the V8 in my truck, I ran around without a front shaft for a couple weeks and believe me, a lot of power was getting sent to the rear wheels. They would spin like crazy. If there was slipping, there wasn't much. I now have a front shaft installed, and I see no signs of damage, the front end gets plenty of power, although I still wish it got none. lol

I would really like to know what is inside these transfer cases. I have looked at the diagrams and analyzed them on my ford cd, but it really doesn't tell me enough.