Mods - ATRAC & Locking rear dif in other than 4L
- Thread starter LWN
- Start date
STLDAVE
Member
Except that the "non trail edition SR5" doesn't have a locker.
Nice work, LWN.
Is there a reason they made the locking rear diff not available in 4H? Are there any concerns of it not being good mechanically for the system at high speeds? Is it just a fail-safe against accidentally driving on pavement with the rear diff locked, since it might be easier to forget you are in 4H as opposed to 4Lo?
Otherwise, this is definitely on my list as well
I would guess that Toyota's reason for not making the rear diff lockable in 4H relates to the speed you are operating the vehicle at while in 4H. If you lock the rear differential then you loose the ability for the wheels to turn at different rates of speed. This can be especially bad while making turns on high traction surfaces.
I only have atrac on my limited, but my tacoma had a locking rear diff which I mainly used on steep hill climbs in 4L. We don't really mud out here unless you want to bury your truck.
Before you do this you should keep in mind that at higher speeds than 5mph you should minimize turns, unless you want axle damage. Plus you really should have good tires on the 4runner first.
GrantK
New member
There is another reason they are blocked in 4H. The traction system works by applying brakes to spinning wheels so power is transfered to the wheel(s) with traction. Do this at a high rotational speed and the sudden change in power transfer from the spinning wheel to the one getting traction can do nasty things to the axles, half-shafts, etc. This was encountered with some more-money-than-brains-yuppies that bought Hummers, got stuck and hit the brake pedal to get traction while spinning the wheels like crazy.
That said, I plan on this mod with the knowledge that I have to be careful and should disable ECU activated traction control.
That said, I plan on this mod with the knowledge that I have to be careful and should disable ECU activated traction control.
adam2562
New member
Any luck of this mod working on the Limited models? ATRAC will ONLY work in 4L right? ATRAC essentially acts as an electronic diff by applying brakes to the spinning wheel thus enabling the stopped wheel to turn right? so if we mod it to work with 4H then we would have those advantages without needing 4L! and not worrying about the rear locker being an issue.. ATRAC is essentially electronically doing that from what i gather.. any input please share!
Skeletor03
New member
If you are talking about the switch lowest in the pic then you should probably re-read the thread as you missed the whole point.
-bh
Skeletor03
New member
To be honest, I checked my manual and it is not in there. Thanks for the info.
GrantK
New member
Try looking on page 330 in the 2012 UM
Gabex35
New member
Does anyone know how to locate the diff lock module? I did this in my fj and want to do it in my 4r. Rear diff lok on demand hack - Toyota FJ Cruiser Forum
I just want locker anytime. Don't really need the atrac
Basically I'm looking for the "blue box" or it's equivalent shown in the fj thread.
I just want locker anytime. Don't really need the atrac
Basically I'm looking for the "blue box" or it's equivalent shown in the fj thread.
harper7
Senior Member
huh?
Pretty sure nobody has done in it on a 14" yet but should be the same as 10-13's .
Not sure if you READ this whole thead or wanting somebody to come over,take your dash apart and point at it. LWN's post #8 in this thread (it's in the mods sticky too)has diagrams,schematics,step by step and high res pics with a big red arrow pointing at it . Let us know if it's different for 14's.................http://www.toyota-4runner.org/5th-g...ocking-rear-dif-other-than-4l.html#post540503
Gabex35
New member
I guess I'm not sure if the 4wd ecu (from post #8) is the same as the "blue box" from the fj thread. I guess I will compare it to the photos once I get it all apart.
In my fj (like the thread link) I was able to ground one wire to engage the locker in all modes, ATRAC wasn't really involved. I didn't really want to have to add an additional switch but may have to on this vehicle.
Canazes9
New member
I'll offer a counter opinion on this modification and some of the discussion I've read to this point (starting w/ the latter)....
W/ regards to engaging A-TRAC at higher speeds and possibly causing damage or control losses - you won't. That's not how A-TRAC works and I think some people are confusing the functionality of A-TRAC w/ TRAC / VSC. When you feel wheel spin in 4Hi and you bog it isn't because of braking - its because the ignition is getting cut by the computer.
The braking applied to the wheels to direct power to the other wheel on the axle in A-TRAC mode is minor and is not at all equivalent to riding the brakes or using an e-brake to distribute power. You are not loading the drivetrain, no more than driving a vehicle w/ an old fashioned LSD w/ clutch packs is loading the drivetrain. The clutch's in a LSD diff don't provide any noticeable drag to the drivetrain - they provide just enough drag to the wheel that is spinning so that power is diverted to the wheel w/ traction. There is ZERO attempt to stop wheel spin - just to balance it across the axle.
A-TRAC works exactly the same way, but instead of using clutches, it uses the vehicles brakes which are much easier and cheaper to service - very cool system! A-TRAC also works better than any LSD that I'm aware of, providing tighter balance of wheel spin across the axle. Again there is ZERO attempt to stop wheelspin, A-TRAC balances it across the axle. If you can't get grip with either tire, the tires will spin (vigorously). This will NOT cause any drivetrain damage in and of itself.
Vigorously spinning the tires does have the potential to overheat the system if done long enough and vigorously enough. I've done this spinning up a wet rocky mountain slope in my Tacoma. A-TRAC was doing a spectacular job pulling the truck up through the rocks w/o the rear e-locker and I was getting a little to joyful and exuberant w/ my throttle. The A-TRAC light flashes when the system is overheated and A-TRAC disengages. About 2 minutes of cool down and everything was fine. I continued on w/ more sensible throttle input and never had the problem re-occur.
With regards to the e-locker and use at higher speeds, this is the same e-locker that Toyota puts in their Tacoma Pre-Runner TRD OR models. These are two wheel drive trucks w/o a low range. My opinion on the reason that Toyota does not make the locker available except in 4L on the 4wd platforms is not because of safety or handling, but rather perceived use. They expect that if you are using the locker you are in a serious traction problem and will be in 4L.
Now for my opinion on performing these mods to my vehicles - I have no use for them. In loose traction conditions like mud, sand and snow (off road), 4Lo will easily drive the vehicle in speeds in excess of 20mph w/o over working the motor/drive train. I just don't believe that wheel spin across an axle is a significant problem at speeds above 20mph - you are not experiencing wheel stoppage at those kind of speeds, LSD/Locked Diff is not going to help you (and you are significantly increasing the potential to break something w/ the locker). For situations where the traction advantage of A-TRAC/locker is needed you should be in low range.
I know what's coming next - those who have performed this modification swearing I don't know what I'm talking about! It makes a huge difference driving in sloppy mud/sand at higher speeds. I don't doubt these experiences are true, just not for the reasons you think. When you trick the computer into believing it is in 4Lo it de-activates the traction control and VSC. Now your throttle won't cut out on you when you slide or the wheels spin while you are in 4Hi and the performance improvement is immediate and very noticeable.
Only problem is you can achieve the exact same thing by pressing and holding the Trac Off button for 5 seconds while stopped. Lots of people don't realize that you have to press and hold in order to shut the VSC off, so consequently, every time the vehicle slides it cuts the ignition and bogs the motor.
In conclusion - Modifying A-TRAC to work in 4Hi won't increase potential to damage to your system. Modifying e-locker to work in 4Hi won't damage system in and of itself, but higher speed operation does increase potential for damage with any locker, regardless of gear range in use. Despite the fact that there is little increased damage potential, I don't see any performance gains to making this modification. Toyota has thought the systems through pretty well and they work well.
David
W/ regards to engaging A-TRAC at higher speeds and possibly causing damage or control losses - you won't. That's not how A-TRAC works and I think some people are confusing the functionality of A-TRAC w/ TRAC / VSC. When you feel wheel spin in 4Hi and you bog it isn't because of braking - its because the ignition is getting cut by the computer.
The braking applied to the wheels to direct power to the other wheel on the axle in A-TRAC mode is minor and is not at all equivalent to riding the brakes or using an e-brake to distribute power. You are not loading the drivetrain, no more than driving a vehicle w/ an old fashioned LSD w/ clutch packs is loading the drivetrain. The clutch's in a LSD diff don't provide any noticeable drag to the drivetrain - they provide just enough drag to the wheel that is spinning so that power is diverted to the wheel w/ traction. There is ZERO attempt to stop wheel spin - just to balance it across the axle.
A-TRAC works exactly the same way, but instead of using clutches, it uses the vehicles brakes which are much easier and cheaper to service - very cool system! A-TRAC also works better than any LSD that I'm aware of, providing tighter balance of wheel spin across the axle. Again there is ZERO attempt to stop wheelspin, A-TRAC balances it across the axle. If you can't get grip with either tire, the tires will spin (vigorously
). This will NOT cause any drivetrain damage in and of itself. Vigorously spinning the tires does have the potential to overheat the system if done long enough and vigorously enough. I've done this spinning up a wet rocky mountain slope in my Tacoma. A-TRAC was doing a spectacular job pulling the truck up through the rocks w/o the rear e-locker and I was getting a little to joyful and exuberant w/ my throttle. The A-TRAC light flashes when the system is overheated and A-TRAC disengages. About 2 minutes of cool down and everything was fine. I continued on w/ more sensible throttle input and never had the problem re-occur.
With regards to the e-locker and use at higher speeds, this is the same e-locker that Toyota puts in their Tacoma Pre-Runner TRD OR models. These are two wheel drive trucks w/o a low range. My opinion on the reason that Toyota does not make the locker available except in 4L on the 4wd platforms is not because of safety or handling, but rather perceived use. They expect that if you are using the locker you are in a serious traction problem and will be in 4L.
Now for my opinion on performing these mods to my vehicles - I have no use for them. In loose traction conditions like mud, sand and snow (off road), 4Lo will easily drive the vehicle in speeds in excess of 20mph w/o over working the motor/drive train. I just don't believe that wheel spin across an axle is a significant problem at speeds above 20mph - you are not experiencing wheel stoppage at those kind of speeds, LSD/Locked Diff is not going to help you (and you are significantly increasing the potential to break something w/ the locker). For situations where the traction advantage of A-TRAC/locker is needed you should be in low range.
I know what's coming next - those who have performed this modification swearing I don't know what I'm talking about! It makes a huge difference driving in sloppy mud/sand at higher speeds. I don't doubt these experiences are true, just not for the reasons you think. When you trick the computer into believing it is in 4Lo it de-activates the traction control and VSC. Now your throttle won't cut out on you when you slide or the wheels spin while you are in 4Hi and the performance improvement is immediate and very noticeable.
Only problem is you can achieve the exact same thing by pressing and holding the Trac Off button for 5 seconds while stopped. Lots of people don't realize that you have to press and hold in order to shut the VSC off, so consequently, every time the vehicle slides it cuts the ignition and bogs the motor.
In conclusion - Modifying A-TRAC to work in 4Hi won't increase potential to damage to your system. Modifying e-locker to work in 4Hi won't damage system in and of itself, but higher speed operation does increase potential for damage with any locker, regardless of gear range in use. Despite the fact that there is little increased damage potential, I don't see any performance gains to making this modification. Toyota has thought the systems through pretty well and they work well.
David
Youngerarlaw
New member
Good work David
Zeder
Member
I just want to put a "Trigger" button on my shifter handle that engages the locker while I have the button pressed. Kind of like a Nitrous button but just for the locker. Strictly for doing donuts in the winter. Of course then it also have to disable trac control at the same time. I could see that button being a fun button in the mud as well.
I spliced the blue wire and the black wire together and hooked them up to a switch. the 4WD ECU does infact register both 4wd and 4lo and you can engaged the locker in 2wd.... However when the switch is on and you run the the vehicle in 2wd it throws a CEL, and when in 4wd with the switch engaged the the CEL is thrown. Has anyone found a way to make the elocker work in 2wd and 4wd, with out throwing a CEL?
Hey Gabe
Did you ever figure out if it was possible to do the mod from the FJ on the 4runner TE?
