4low-trac

do this many people actually get to use 4lo on a daily basis? I only use it offroading lol. Yay for IL.

 

I would think major computer swapping would be needed to make a TRAC truck ATRAC. probably not worth it

 

curious why you think this?

 

ATRAC is a different set of components controlled by a different VSC computer. It has more accurate wheelspeed sensors, a larger mechanical brake booster and so on. It is not a case of "activating" anything. Short of a huge project, installing all the different components, and all the wires, circuits, sensors, and VSC unit, it is essentially not do-able. ATRAC is a "tighter" system, my experience so far tells me it is probably superior, but I've noticed it transfers power so quickly, (like a locker engaging), it actually causes more slip on the side with traction, than TRAC does.

 

^^what he said

 

thanks for the info.

 

Looking at that schematic, it appears you guys are cancelling the only signal that tells the 4WD ECU that the actuator has completed the shift from 4hi to 4lo. If so, what stops the 2-4 motor from constantly trying to shift into 4lo? It doesn't look like there is any sort of fuse or breaker in line. Seems like it would burn up that actuator motor pretty quickly. What am I missing?

 

its not really the 4wd ecu its the traction controll ecu. the wire is supposed to tell the ecu that the truck is in 4lo and to turn off trac. If you cut the wire it wont get the signel and leave trac on. The motor gets the signal from else where. If the truck doesnt go into 4lo it will still beep indicating a problem with engagement.

 

in the ADD control there is a limit switch that does not allow the motor to keep running. if the motors goes in it moves the actuator x amount, if the gears are not lined up and it doesnt go in all the way it will beep. the motor does not keep running. I have left my truck in 4lo for hours with no issues.

 

Exactly, the beeping is telling you that it has quite trying to engage and that you need start the process over. If 4lo is blinking and there is no beeping, I bet you those leads at the actuator motor are still hot and trying to finish the cycle.

 

well i hear the concern and i will check it out today because i dont want to cause damage. The way the actuator is design is it turns x amount. if there is back pressure it stops if it completed its cycle it turns off.

Bad EX but: its like a garage door you push the button and it goes through a cycle and stops. If the door hits something it knows and opens back up and the light flashes.

The actuator wire is always hot. the switch activats a solanoid which turns the motors when the motor turns a set amount it stops. it does not rely on the signal to tell it to stop.

 

Yeah, I'd check it. I know that schematic is an old one, but it shows that signal wire feeds the 4wd ecu first, on the down side of both the ADD actuator and the transfer shift actuator assembly.

 

The A.D.D. actuator is under constant voltage when engaged, and to disengage, it de-energizes. So the ADD functions as designed, this wire does not affect that. Again, this is just a signal wire to the VSC.

 

I'm talking about the power to the actuator assembly that shifts from hi to lo, not the ADD which is engaged whenever it is 4wd, it doesn't care if you are in 4hi or 4lo. The motor I'm talking about turns one way or the other, being controlled by the 4wd ECU.

 

To elaborate, this wire reports the transfer case shift position, the ADD position is reported via a different wire. Both (ADD & T-Case), are actuated at an electrical point before the reporting signal is sent. The electric actuation occurs independently of these non current carrying wires, and that funtion is unaffected by what these wires report.
Hope this clarifies things. I was avoiding discussing this level of complexity, simply because the system functions identically in 4WD.....
The flashing light can probably be fixed with a 1000k resistor in series with ground......

 

Well it is "technical chat." What is the purpose of the transfer indicator being ran into the 4wd ECU then? On the 09 and up models, is the transfer indicator signal wire for the VSC (the one you clip) coming from the transfer indicator switch or from the 4wd ECU? And why do the disable VSC in 4lo to begin with?

 

It comes from the ECU. The purpose of it, is what we're bypassing. It's there to de-activate the VSC. Why? probably because it interferes with off roading. I don't really know. Why TRAC de-activates is anyones guess. Could be the same reason ATRAC used to shut off with the locker pre '09, and now it doesn't......Seems like an oversight, like no heated mirrors, explain that one.....As well, the transfer indicator reports to the ECU if it has engaged, if not, it beeps.

 

Gotcha! I thought you guys were clipping the signal wire from the actuator system to the ECU (the only one on that '06 schematic), I didn't know there was another one from the ECU to the VSC system. It's wacky to turn it off in low range, unless there is some physical reason regarding the non ATRAC vehicle's braking system. May have to do with the reason ATRAC vehicles don't have the vacuum booster set up on them. Mine's got the ATRAC, but a buddy of mine has an 09 4 banger regular cab 4X4. He may try the mod.

 

I took a close look, calling the actuator a motor isnt entirely accurate. It is technecally a servo. It has and internal gear box driven by a motor (rack and pinion) the rack moves back and forth. It has a sensor that measures the position of the rack. The switch tells the servo at what position to move the rack. 2hi all the way out, 4hi half in, 4lo all the way in. If the gears arent lined up, the clutch isnt depressed, or the ebrake is on it will beep and the rack does not actuate. To verify i did it with the truck off. You can here the solonoid click and the servo moves and the solonoid clicks off. It does this from 2hi to 4hi and to 4lo. So the motor does not continue.

 

Cool, that is what I was wondering. In that schematic Toyota refers to the motor at the heart of the actuator assembly as the "2-4 motor" and being controlled by the ECU. From what you are describing, the ECU is just initiating the shift, not controlling the entire assembly process. If the solenoid clicks off after the shift to low range, it should be good to go.