Converting Aviator to A4WD?

[Wrench Wench]

I just glommed onto a 2005 Lincoln Aviator Luxury for $1500. I've read up lots on the transfer case and its infamous viscous coupling. What other transfer cases for this vintage of UN152 platform fits and works in an Aviator for A4WD operation, rather than AWD, so I can get rid of my viscous coupling? I'm looking at things like the BW4405/6, which I know will need its own control module and the push buttons for the dash, but can I just swap its control module in place of the TOD control module of the stock Aviator? Or would I need to graft the A4WD control module between the stock control module and the TC by some Frankensteinian means?

Full disclosure, I'm only going to be a Lincoln Aviator owner temporarily. I bought it for its drivetrain, which I intend to modify and graft into a Crown Vic/Grand Marquis to make a 4WD, 4 wheel independent suspension Mercury Marauder-alike.

 

[CDW6212R]

The AWD units are plenty strong, the only possible problems are idiot owners who allow the tires to wear unevenly(which is what ruins the viscous clutch over time). The BW4410 AWD you have is likely as good as the prior BW4403 and BW4404 that came out in the mid 90's. The viscous clutch may be the same unit, they are a sealed component. If the fluid becomes black, that is a majority of the time result of the viscous clutch leaking out it's fluid(and the clutch material with it).

The A4WD models all have a special GEM module for that 4WD, plus the TOD and 4WD modules. You could likely fit that into the Aviator to make that work, but for a drivetrain swap, I'd consider something else.

The trans in the Aviator is unlike prior Ford transmissions, the transfer cases are different. So the TC's you may use will have to come from other 2002+ Ford models, I only know that AWD model 4410 name. They all have very large mounting pads that attach to the trans, below is a picture of a BW4410 TC.

BTW, the AWD TC is smaller than a 4WD TC of any kind, not a lot but some. That will matter if you are trying to fit it under a car. Personally I would choose between a 4R70W trans, or a 6R80 six speed, which both have aftermarket controllers available.

 

[Wrench Wench]

I already figure I'll need to cut out the Aviator trans tunnel to graft it into the Ford Grand Aviator, but I'm also making the FGA into a LWB model, so I should have plenty of space, above and below the floor. I also plan to use the Aviator front seats and console with the floor shifter in the FGA, which again would benefit from having the trans tunnel it's used to being mounted to come along for the swap. As I understand it, the Panther platform is 8" wider than the UN152, so I should have plenty of space to arrange the seats and console to make it sensible in a sedan. Only snafu there that I'm unsure of is the power seat controls/connectors. The FGA will have the same power seat controls on the door, but they appear different from the Aviator, which makes me expectant that the connector underneath might be different as well. Maybe just a repin, but I'm expecting to have to pop all of the pins out of the Aviator seat connections and pop them into the connector harvested from a Panther power seat to make it plug and play.

As for the TOD signal, I'm relatively certain it's just a 12VDC constant power, which I can use to trigger a A4WD unit to go into locked 4WD mode for a very similar effect. The thing is, I'm not certain what the TOD signal does in the BW4411, electro-mechanicly. I've watched people tear them down on YouTube, but I never remember seeing any electrical connectors.

I'm a certified CNC machinist, so I've been thinking about how I might build a drop-in electricly locking differential in place of the viscous coupling. The problem that I have with them is two fold. 1) Sometimes, I'd kinda like to have 2WD with the front hubs unlocked. (I know the Aviator, as an AWD vehicle doesn't have front hub locks.) and 2) getting more than 3/16 of an inch difference in circumference is the difference between a couple of PSI of tire pressure or a couple of 1000 miles of wear for the fronts (supporting the engine) and the rears (supporting an empty cargo area). If that's all it takes to fry one, it doesn't sound very reliable to me.

I'd have no real problem replacing a transfer case control module for whatever 4WD TC I eventually get. My only issue is for digital comms with the PCM. I've worked in embedded software engineering in the automotive sector, but I don't know the specific CANBus (assuming it is CANBus and not J1938 or something else) formats for the PCM sending commands or requesting data from the TC control module, or vice versa. I have no problem cobbling something together that will trick the Aviator PCM into thinking the TC control module is hunky dorry 24/7/365 and just using my own data interconnect to diagnose any defects with the TC.

 

[CDW6212R]

The early 2000's Fords are still okay to work with the electrical communications stuff, fairly. Look into some engine swap of Sport Tracs with the older 302 Explorer systems. They are able to make the dash and GEM systems work with the older less complicated PCM etc. You're getting p closer and into the CANBus stuff, which is bad for amateurs like most, and me.

The AWD I've had several of in my 98's and 99's, I typically have tires that are 1/16" or so different front to back, when I rotate them. That level won't hurt the AWD, but you know some people love to buy two new tires when they run their cars so long that two are bad, and two are not so bad. Who knows if it was the old set of four, or the obviously mismatched two new ones that killed the AWD. The only one I've had be bad was that way when I got it, the front drive shaft removed. They told me it had been out for almost seven years. The TC fluid was black, so the damage had been done years past. We often have people here with "new" 2nd gens that ask about tires, or symptoms, that turn out to be mismatched tires. So what kills the AWD, the limit isn't known. But so far I think it's really careless owners who pay no attention to tires, or care.

The 6R80 trans is in many 2012+ trucks and Mustangs, I would wonder about those 5.0 platforms, more than the DOHC 4.6's and their transmissions. The 4WD TC and operating system sounds like the little hiccup to work out. The TOD module is about the speed sensor and shift motor, I agree I think it's a minor module as part of the 4WD and GEM.

 

[Wrench Wench]

I'll need to get the DOHC and 5R55S swapped over to the FGA and run it for a while before I could decide if it's worthwhile to go for a 6 speed auto.
I really wanted a T-56 6-speed manual, but it's so expensive, I'll have to wait a while when I have both my current Panther platform beater and the FGA fully sorted before I even think about a T-56 manual swap in one of them, and then, it'll prolly be the beater. Having the 5R55S alone would be better than the 4-speed that came in the stock Mercury Marauders. Plus, the Panther weighs a full ton less than the Aviator the drive train was born propelling, so the stress on the trans and TC should likewise be lessened.

I know the TOD is supposed to be triggered by the PCM sensing a difference in wheel speed between the front and rear wheels and then it's supposed to take a standard torque split of 70-30 (Edit: 60-40) to 50-50 until the wheel slip ends, but I don't know how the TOD signal affects that change in the TC. The 4411 doesn't have a shift motor that I am aware of.

 

[CDW6212R]

Yes, the 5R V8 transmissions are better geared than the 4R, I wish they had a stronger reputation. I think they are adequate if the power doesn't get too high, like the 03/04 Cobra would be. We have a member here using a rebuilt 5R55E, and 18-20psi of boost, with no failures yet. Luck may be part of any transmission, who knows.

Good luck with that project, I love those Marauders etc. I have a steering column and wheel going into my 92 Lincoln, I'm after the steering wheel and it's controls, the radio and EATC etc. I do wish Ford had made some form of car AWD, for the components that could be swapped backwards. What they did make are very big in volume, not ideal.

 

[Wrench Wench]

I intend on running full rebuild kits on both the DOHC 4.6L and the 5R55S by the time they're ready to be stabbed into their new home in the FGA. That'll mean every seal brand new, piston rings brand new, solenoid pack brand new, any components that look at me funny brand new. I'll also take the opportunity to paint the reassembled units from engine block to TC so any leaks will be apparent. I hope to get the assistance of the local community college automotive technology program with the rebuilt process, but I'm not overly optimistic. I expect to get more power out of the DOHC than it was born with, but again, with a ton less to haul around, I don't expect to overly stress the 5R55S while it's under a Panther platform sedan.

If I get really bored, I might even take one of the spare rack and pinion units laying about and work up a remote servo and steering input sending unit to see if I can make it 4-wheel steering as well. I guess it depends on how long the pandemic and my unemployment holds out.

The Crown Vic LX going into the FGA has full steering wheel buttons, but I was planning on putting that in my beater. I'll need to source a new 1999-2004 steering wheel with full controls for the FGA to get what I want there.

 

[CDW6212R]

I have only about one spare part for those, I got an NOS steering wheel that was the wrong color. Typically, the pictures lied, and I didn't want to send it back in case I never found the right color. I wanted medium grey, and the first one ended up being the darker grey. I found a proper grey one later, so the extra one like many things, I haven't gotten around to selling. I bought the rear brakes from a 2004 CV years back, not knowing how different the parking brake and cable was. That may be workable on my 98 Explorer, but I also might use them for my Lincoln. That 2003-06 platform had a lot of good upgrades in it, and just now are becoming scarce in JYd's.

 

[Wrench Wench]

As I'm likely to wind up trying to mix and match seats, steering wheel, dash, console, interior plastics, carpet, headliner, etc. across name plates as well as years, I'm just figuring on using rattlecan vinyl and leather dyes to render everything an even, dark gray and be done with it.

 

[CDW6212R]

Yes, a daily driver, most of mine are that way, with a few odd parts stored away for later.

 

[camodown]

TOD works via PWM of electromag clutch on input shaft of trans case. 4x4 High is attained via 100% duty cycle to clutch. The shift motor only function is range select to move shift fork in and out of low range. The clutch sees 100% duty cycle in low range as well.

02-03 model years used a Motorola 4x4 Control module for TOD transfer case. 04-05 switched to CANBUS as well as using pcm and instrument cluster in place of 4x4 control module. Gen 4 went back to seperate 4x4 Control module.

Auto 4x4 on 02 and 03 used input and output speed seensors to determine front and rear driveshaft speed differences and apply varying duty cycle to clutch for 4wd. The move to IVD, or Advancetrac coupled with RSC got rid of a rear diff mounted VSS and moved to a more complex monitoring system via 4 wheel speed sensors. Two front integrated tone rings in unit bearings (on all U152s) and two rear tone rings on outboard CV wheelend. IVD also made way for an additional sensor and different master cylinder and ABS HCU for control of braking system to assist moving torque side to side for traction in addition to an induced chassis upset mode to maintain yaw stability in a calculated "rollover" incident. This locks up one or more wheels momentarily to induce a significant yaw and stabilize chassis.

A few other notes, 02 and 03 4.6L were not drive by wire for throttle. 04 and 05 added drive by wire (throttle control for stability and traction control), As well, Advancetrac with RSC added a gyro for stability control at center pivot point of vehicle for yaw measurement in addition to an electro-optical sensor with trigger wheel to measure steering angle.

For 4wd, Certain calibrations used less than 50% duty cycle to electromag clutch even in 4 high and when engine load and driver calculated power demand increased, duty cycle would increase. It was determined differential wheelspeed calibrations were too sensitive in certain 04 and early 05 MY and so a reflash was broadcast for "false 4x4" engagements typically seen with steering wheel at lock and throttle applied low speed.

Anyway, got a bit off into the weeds.

 

[Wrench Wench]

So, I guess I have to wait until I can take possession of my Aviator to figure out if I have a TOD 4x4CM or what and then I can start to figure out how I can swap out what I have for what I want as well as how to control it without having the PCM freak out. I would probably be better served having the PCM reflashed to ignore 4WD operations entirely and leave that up to a custom 4WD control module.

PWM to electric clutches makes a lot of sense for a system intended to go from 100% RWD to 50/50 4WD continuously. The drop-in that I was imagining would have the chain drive be on one electric clutch and a differential locker on another. If the chain drive clutch is to be off-full (2WD), the diff locker would have to be on-full. Once the chain drive clutch is on-full, AWD would be affected by selectively engaging the diff locking clutch to varying degrees. Rear wheels would always receive power. Front or rear slippage would engage the diff clutch to take power away from the slipping end and toward the end with grip.

To make it essentially a drop in for the viscous coupling, both output shafts would have to exit the diff in the same direction, meaning the front drive output would be a hollow shaft with the rear drive going through it to the rear coupling to the drive shaft. The outer shaft/front drive would engage the chain drive through the 2WD/4WD PWM clutch. As far as I know, Aviator TCs never had a low-range. It was just an AWD system.

Catastrophe would occur in my system if neither TC clutch could be activated, as that would disconnect the front drive while allowing the differential to spin the front drive input freely, resulting in no torque delivered to the rear wheels either. A solution could be to make the diff locking clutch engage by default, under spring power, and the electric clutch would be to selectively disengage the diff locker until excessive slippage is detected. I'm also interested in the possibility of using vacuum power to activate the clutches of the TC.

 

[CDW6212R]

The transfer cases all have full time connection to the driven end, RWD up until the 5th gen Explorers which were FWD unless the TC engaged the rear.

Those TC's with an electromagnetic clutch, that is simply in line for the output shaft for the front drive. There is no differential in the TC's, no locking function of such a diff. The rear is always driven, and the chain runs the forward output shaft, in the left side position under the driver. The AWD viscous clutch is in that section, as is the electromagnetic clutch for the A4WD TC's.

 

[Mbrooks420]

4WD Electronics

I was wondering if someone who is a little more experienced with the electronics side of the A4WD system of the 2005 explorers could tell me what all is incorporated into the system. Obviously there is the dash switch, but is there also 4WD module behind the dash.

www.explorerforum.com

Is this about the same swap?

 

[Wrench Wench]

4WD Electronics

I was wondering if someone who is a little more experienced with the electronics side of the A4WD system of the 2005 explorers could tell me what all is incorporated into the system. Obviously there is the dash switch, but is there also 4WD module behind the dash.

www.explorerforum.com

Is this about the same swap?

I don't think that person is asking after a swap project, but the answers to his questions would help inform my swap project.

 

[Wrench Wench]

The transfer cases all have full time connection to the driven end, RWD up until the 5th gen Explorers which were FWD unless the TC engaged the rear.

Those TC's with an electromagnetic clutch, that is simply in line for the output shaft for the front drive. There is no differential in the TC's, no locking function of such a diff. The rear is always driven, and the chain runs the forward output shaft, in the left side position under the driver. The AWD viscous clutch is in that section, as is the electromagnetic clutch for the A4WD TC's.

Yes. I'm talking about replacing the viscous coupler with a locking diff, among other mods, that would otherwise maintain the 2005 Aviator transfer case's exterior and function, but I'm doing my thought experiments based on a tear down of an Explorer TC that appeared to have no external connectors whatsoever, so I'm probably thinking badly. I need to wait to see what is actually between the frame rails of my Aviator when delivered to know what I actually have and then know far better what route I should take to get to where I want to be, which is an A4WD. If that means major mods to the TC I get in my 2005, so be it. If that means the wholesale replacement of the TC and supporting electronics, so be it. Even if it means a reflash of the PCM to keep it from wigging out when it doesn't see the stock TC control electronics.

From what camodown was saying, it appears the TC controls in the 05 is integrated into the instrument cluster. Since I'm probably not going to be able to swap an Aviator instrument cluster into the dash of a Grand Marquis, I'll need to come up with something else. However, my automotive embedded software engineering background has been leading down the path of a possible homebrew digital dash using a Raspberry Pi, CANBus transciever, 14" 4K stretched touchscreen LCD, and Automotive Grade Linux. So, if I can make one that the PCM will talk nice to, that may be sufficient.

Something else camodown said though, doesn't jive with my own understanding. While the Panther platform for 05 did go to throttle by wire, the Aviator for 05, to the best of my knowledge did not. All photos I've seen of 05 Aviator throttle bodies looked just like 04 Aviator throttle bodies, i.e. direct linkage throttle cables. Perhaps he was referring to the 05 Explorer?

I have no idea what IVD is, and I don't think the 05 Aviator has Roll Stability Control.

 

[CDW6212R]

Various models had changes made at differing times, so verify any suggested changes. Ford does wild things, changes, for random reasons, so again it's always interesting to figure out what's going on with everything.

You will trouble with the transfer case, because none of them are made with a diff, or an arrangement that splits power like a diff. I'm not expert, but what I've read makes me believe they all have a primary power path, and a chain that drives off of that, to the secondary path. The clutch of some type will always be on the secondary path, so all you can do there is control the application of that one output(front drive in this case). I think you will be choosing a TC based on it's overall size, to do what you can with that.

 

[Wrench Wench]

I don't know if it was standard, but my Aviator absolutely does have AdvanceTrac™ roll stability control, so any TC alterations I make will have to take that into consideration.
My Aviator was listed as the base model of Luxury, but it has a lot of options. Does anyone have a canonical list of options that went into the *checks notes* Ultimate package for 2004? 2005 dropped the higher tier "Premium" and "Ultimate" packages and just had the schedule of options. Mine is very thoroughly optioned. I know the DVD navigation and rear passenger DVD entertainment options are in it and those were higher tier in previous years.

Looked over the Owner's Guide. Still don't know how to open the rear liftgate from the outside without power.