Power source that comes on when in 4wd?

[wfo9]

Anyone found a way to tap into a power source that only turns on in 4wd (when the ADD is on...) I can probably figure something out, but why re-invent the wheel.

The reason is that I'm a little concerned about my front locker accidentally engaging in 2wd and would like to wire in a safety relay that would only allow the solenoid to open while in 4wd.

The front locker currently requires me to turn on the compressor and the rear locker before the front solenoid will power, but sometimes I leave both locker switches on and use the compressor switch as a master control. So if I accidentally hit the compressor switch going down the road in 2wd it would most likely be a disaster.

 

[mo_mo]

Sorry for not answering your question, but doesn't ADD prevent disaster since the left wheel is disconnected? Are you concerned that ADD isn't working right and engaging the air locker?

 

[Jetboy]

Seems likely that a relay plus a tap of some sort into the add circuit or the dash light for 4x4 would be most likely way to get your desired power.

 

[Canazes9]

The front locker currently requires me to turn on the compressor and the rear locker before the front solenoid will power, but sometimes I leave both locker switches on and use the compressor switch as a master control. So if I accidentally hit the compressor switch going down the road in 2wd it would most likely be a disaster.

Doctor it hurts when I do this.....


I would be reluctant to tap into the ADD power source, modern electronics can be very sensitive and I would fear it not working properly at a critical time when I needed it.

I believe I would seek an administrative solution.

David

 

[wfo9]

Sorry for not answering your question, but doesn't ADD prevent disaster since the left wheel is disconnected? Are you concerned that ADD isn't working right and engaging the air locker?

No, with the ADD disconnected (2wd mode). The driver side axle spins and the passenger side diff output spins backwards with the drive shaft stationary.

If the locker was on the ring gear and front drive shaft would start spinning.

I'm actually not sure if it would be disaster or not. Really depends on whether or not the transfer case allows the front drive shaft to free wheel when in 2wd. I don't want to find out the hard way what happens. .


Occasionally I hit the real locker while in 2wd while on dirt roads... trying to get up a hill. I know it is just a matter of time before I fat finger it and accidentally hit the front locker. That is the reason I'm trying to make it idiot proof. And yes, I'm smart enough to know that I'm often an idiot when not paying attention to what I'm doing. It happens to everyone somewhere along the way.

[MENTION=78273]Jeremy556[/MENTION] You tried or thought about this scenario.

 

[bimrunner]

ARB has it wired so that the rear locker is required to be engaged or the front will not engage (at least, that's how mine are wired).

Edit: never mind. I read to fast and you noted this already. Tbh, I wouldn't advise leaving lockers on and using the compressor as a master switch. Wouldn't that solve the risk? I only need/use my front locker in extreme situations so I dont leave that clicked on at all. Just use for a very short period and switch off as soon as I don't need it. That's just how I deal with the potential. I leave my compressor on and switch lockers as needed. It is always rear first and then if needed front. Then front off, rear off.

 

[wfo9]

ARB has it wired so that the rear locker is required to be engaged or the front will not engage (at least, that's how mine are wired).

Correct, that is easy.

Have you every accidentally flipped on the front locker (with the rear) while in 2wd?

Oh wait, you have a Limited so no 2wd for you, LOL.

I'm starting to think it might not be a big problem even with the transfer case in 2H. Just not sure what will happen for sure. Might go try it out on jack stands tomorrow and see what the transfer case allows the front drive shaft to do in the 2H position.

On a related note, I was out screwing around the other night with a couple of locals on some trails. We hit this really steep loose climb. All the ones with open diffs could not make it. I thought, this will be easy for me. So I pushed both locker on. Started up the hill and got nowhere (I had ATRAC on). I had the stupid compressor switch off, so no lockers. Had to back up and flip them on then it shot up the hill like a rocket. That is the first time I've had ATRAC fail miserably (it was worse than just hitting it fully open, since this ground required some wheel spin). Another factor was not even being aired down...we were just screwing around while camping...

Back on subject, sometime I preemptively lock based on the struggle i see others having. I see no issue doing front and rear on at the same. I think the caution for the front in general is that its so much weaker than the rear that you would never just want the front on alone with an IFS setup. Turning is also an obvious concern for it.

 

[bimrunner]

Correct, that is easy.

Have you every accidentally flipped on the front locker (with the rear) while in 2wd?

Oh wait, you have a Limited so no 2wd for you, LOL.

I'm starting to think it might not be a big problem even with the transfer case in 2H. Just not sure what will happen for sure. Might go try it out on jack stands tomorrow and see what the transfer case allows the front drive shaft to do in the 2H position.

I think we were typing at the same time. Lol. No, I've never accidentally engaged the front as I follow the same pattern every single time as my edit above notes.

 

[wfo9]

I wouldn't advise leaving lockers on and using the compressor as a master switch. Wouldn't that solve the risk? I only need/use my front locker in extreme situations so I dont leave that clicked on at all. Just use for a very short period and switch off as soon as I don't need it. That's just how I deal with the potential. I leave my compressor on and switch lockers as needed. It is always rear first and then if needed front. Then front off, rear off.

That is what I try to do, but i used those OEM like switches to keep the factory look... Turns out they are a very light touch and it is easy to fat finger one. (was probably not the best choice) Plus, since the front goes off with the rear it is easy to forget to turn off the front switch sometimes (since the lights are really my only visual indicator). For the compressor itself, I used the actual ARB switch which is a rocker, but I mounted it lower and out of the way.

There is also the possibility of someone else driving my truck at some point (wife, parking attendant...) and hitting a switch to see what it does.

This may not even be a concern if the front drive shaft can spin in 2h. I'm starting to think it almost has to allow this, or there would be stories about this happening to others. Surely someone has accidentally flipped one on in 2h.

 

[KGcobra]

What if you mount a micro switch under the console that will be opened/closed depending on the physical position of the 4wd lever? Then wire that switch into your relay using any available 12v circuit.

You could mount the switch so that it's closed when the lever is in 2H, and wire your circuit so the relay is powered when the switch is open to allow your locker in 4H and 4L. Or mount the switch (and set up circuit accordingly) so that it's closed when the lever is in 4L, if you only want the front locker to work in 4L.

 

[Canazes9]

On a related note, I was out screwing around the other night with a couple of locals on some trails. We hit this really steep loose climb. All the ones with open diffs could not make it. I thought, this will be easy for me. So I pushed both locker on. Started up the hill and got nowhere (I had ATRAC on). I had the stupid compressor switch off, so no lockers. Had to back up and flip them on then it shot up the hill like a rocket. That is the first time I've had ATRAC fail miserably (it was worse than just hitting it fully open, since this ground required some wheel spin). Another factor was not even being aired down...we were just screwing around while camping...

I think perhaps you had TRAC on, not ATRAC. ATRAC allows vigorous wheel spin, TRAC does not. Were u in 4Lo?

David

 

[Jetboy]

I'm certain the transfer case allows the front shaft to spin freely in 2wd. It's easy to check. Just put it in 2wd and reach under and turn it.

Also this t-case has been around for a long time and has been used in models with locking hubs and would not have worked properly if it didn't disconnect the front shaft. You can tell because function of moving the lever is to move the shifting fork and engage the front drive shaft gears, but also because if it didn't, there would be no lever. Just a button for the ADD. On the SR5 the button has an electric servo that moves the shift fork where the lever would otherwise move the linkage.

Inside there isn't really very much going on. There's an input shaft that's inline with the output for the rear axle. There is a planetary gear assembly with a collar that can be shifted forward or backward to engage or disengage. Otherwise it's a direct drive straight through. Connected to the rear output shaft is a gear that drives a chain. That gear can be engaged by a second sliding collar. In 4wd mode that is engaged and the chain drives the front output shaft. Because it's connected to the rear output shaft, you can't have front drive only (no front digs ).

But - I don't think you want to engage the air locker when the gears are spinning at 60mph even if the front shaft can spin freely.

 

[wfo9]

I think perhaps you had TRAC on, not ATRAC. ATRAC allows vigorous wheel spin, TRAC does not. Were u in 4Lo?

David

Yes I was in 4Lo. This was a really steep loose rutted hill. I know it allows wheel spin, but I would call it interrupted wheel spin. It's not the same. There are a few scenarios where ATRAC fails (as well as a few where it is the best choice possible).

I may have been able to throttle it better had I known ATRAC was all I had on, but I approached it thinking I was fully locked. It barely went anywhere but I also let off pretty quickly since the feel was much different than what I expected.

The guys who had locked rears only (mainly 3rd gens) had major trouble with this hill, so I don't think ATRAC alone could have made it, but I might go back and try some day just to see what happens.

 

[wfo9]

But - I don't think you want to engage the air locker when the gears are spinning at 60mph even if the front shaft can spin freely.

Agree. I'm not too worried about the hwy speed scenario. My most predicted scenario is me trying to turn on the rear locker while in 2wd offroad.. (but accidentally already having the front locker button pressed in).

I won't spend much time on this, but if there was an easy to find 12v source that powered in 4wd.... it would be nice way to idiot proof it.

My truck has a manual transfer case shifter (not the dial), so I may take a look at that mechanism for including a interrupt switch.

 

[1engineer]

Don't get me wrong here but I think you are adding complexity on top of complexity, never a good idea. I understand what you are wanting and think your goal could be achieved with a simple relocation/replacement of a few switches. A nice covered toggle with return to center or a secondary switch to arm the first switch for example. Anytime you go away from the KISS method you are asking for trouble. Is it a bit more bother to activate in the field? Maybe but how often over a week's time do you actually use that switch? Even off road, how often do you use the front locker? Not a lot I'm betting. A covered switch or a relocated switch would be much easier, safer and simpler.

 

[wfo9]

Don't get me wrong here but I think you are adding complexity on top of complexity, never a good idea. I understand what you are wanting and think your goal could be achieved with a simple relocation/replacement of a few switches. A nice covered toggle with return to center or a secondary switch to arm the first switch for example. Anytime you go away from the KISS method you are asking for trouble. Is it a bit more bother to activate in the field? Maybe but how often over a week's time do you actually use that switch? Even off road, how often do you use the front locker? Not a lot I'm betting. A covered switch or a relocated switch would be much easier, safer and simpler.

Yea, I see your point, but I also like to make things idiot proof. Because we can all be idiots at times (been there and done that too many times to deny it).


I'm going to test things tonight and verify to be 100% sure that the front drive shaft is free to spin while in 2wd. If that is the case I'm not going to worry about any additional idiot proofing.

 

[wfo9]

This may be easier to setup than I thought. Might not be a bad idea regardless.

 

[wfo9]

I tested this out tonight and verified that the front drive shaft is free to spin while in 2wd... So accidentally flipping on the front locker while in 2wd while going slow is not really a problem.

Also the 4wd indicator connector in the above diagram looks to be difficult to get at without dropping the transfer case or having really small hands, so I'm not going to mess with it any further at the moment.

The main thing I was concerned about is not an problem, so the only concern would be flipping on the front at high speed in 2wd and I can't see how that would happen (since I only flip the lockers on and off going very slow).