Lock, Stock, and 2Wheel Low (3rd Gen DIY Mod)

Update:
@lapoltba has a plug and play solution for sale via Group Buy.
https://www.tacomaworld.com/threads...-2wd-low-range-for-the-3rd-gen-tacoma.614743/
Connectors to build your own plug and play are available for purchase, but not cost effective compared to the @lapoltba harness. For low cost, continue to use DIY solution here. For convenience see his plug and play harness. Both mods are electrically identical.

Original Post:
I have successfully modified my 2017 TRDOR Auto to provide 2Wheel Low functionality. Just like the basic methods used previously on the 2nd gen, this method tricks the ECU into thinking the front Automatic Differential Disconnect (ADD) is in the 4wheel position when it is not. The method given here is a basic electromechanical solution, and does not provide the fancy computerized solution that was developed for 2nd gen.

I have attached a pdf giving quick rundown of the installation and a pdf for a replacement visor info card. Note, this mod as written involves some significant hacking into the 4wd electrical harness, so this mod should not be considered for the faint of heart. I spent about 5 hours all in doing the actual mod with some trial-and-error, with taking pictures (not including the many developmental hours).

I can't guarantee this mod works on anything but my truck, but I think any 4x4 3rd gen should be the equivalent. As people find errors please let me know and I will try to keep the pdf updated. Sorry for all the dark pictures in the pdf. Please give any helpful suggestions, that is how we make things better.

I still dream that maybe somebody will have a better solution than this, but I am not holding my breath.

For reference, the main usefulness of this mod is reversing the MT with a trailer, and pulling boats out of the water at boat ramps on auto and manual, as far as I am concerned.



Enjoy

Installed/tested compatible
2017 TRD-OR Auto Access Cab (dev truck)
2018 TRD-OR Manual Access Cab
2016 Sport Manual Access Cab



[Edit for alternatives:
A possible retrofit for locking front hubs has been investigated. I have not done these mods and do not provide any warranty on appropriateness or usability on 3rd gen. Just listing here for helpfulness.

https://www.tacomaworld.com/threads/fs-manual-hub-conversion-kit.511528/page-9#post-17494241

https://www.tacomaworld.com/threads/free-wheel-hub-conversion-3rd-gen.513930/

Thanks @tonered
/Edit]

[Edit 4/5/18] Edited pictures for improved clarity [/edit]

[Edit 5/31/21] Edited pdf page 7 text, removed error in text to grounding Pin 12, thanks @pdcornell. Rolled instructions to rev 1.1]

 

Saved for future discussion

 

Awesome! Could you now figure out a mod so I can engage the locker in 2wd? Pretty please?

 

Can you like this more than once ?

 

Excellent!

Yeah, what @edgerat and @Frankenstuff said! UpUp!

 

@TeecoTaco @Joe23

 

just saw this before you tagged me.

Don't see a need for it. If i towed or had a boat maybe would be good for docks but offroad dont see a point, would just be in 4lo

 

Ya, main thrust of this is MT reverse under load. The reverse ratio is a tad aggressive in the MT (only real complaint of MT owners)...2WD low when maneuvering a trailer in reverse under stress would alleviate this awkwardness and being 2WD would minimize binding of 4WD in low whilst navigating a trailer.

Stems from the 3 stick days with manual locking hubs...the more configurations the better when they're at our fingertips control vs a computer deciding what ye shall have

 

it's actually pretty handy off-road to be in 2 lo. There are times when you need the gearing without the front drive, and without the front pulling, it turns much easier.

 

In my experience, a locked rear end and open front is alarmingly capable off-road.

 

Thanks! That is just some awesome work.

I'm a real novice when it comes to electrons but have been getting more confident. Given the amount of exposed wire on those connectors, this REALLY looks like a pretty simple mod. I like that relay and mount also.

Comparing this to Up2NoGood's design, which has some logic built into it that eliminates the switch, this is pretty elegant.

My biggest limitation right now is a switch position. I need / want a couple blanks. At least one below the 4wd knob would be great and one up top for the garage door opener mod is on my wishlist.

Mesojdm has some sweet lower switch panels that now need to get serious about.

Thanks again!

 

I love the elegance of @Up2NoGood 's mod and wish he had a 3rd gen version. Unfortunately it looks like the 4wd ECU connectors are different from the 2nd Gen, (just from a glance so don't hold me to it), so I assume that it would be a big pain to get the new connector to allow his mod to give plug-and-play. Also, I don't think his solution has the resistor that 3rd gen seems to need, but I think that would be relatively easy to add.

If we could find the ECU side of these connectors for 3rd gen, a plug-and-play solution (at least electro-mechanical solution at a minimum) would be relatively easy. I tested a plug-and-play solution for 3rd gen that spliced in near the front differential ADD in the engine compartment, but it was just too exposed to water for my liking.

I want to install the switch up high next to the other traction control stuff (on the OR), but it was a quick first solution where it is (for me).

 

BTW, I have heard absolutely zero comments about the visor reference card. Anybody like the inclusion of the traction control modes, or want it displayed differently?

 

Exactly. That was what Up2NoGood found briefly looking into the 3rd Gen also.

Honestly, the switch in your version is not a big deal to me at all. The main hang up is the delays of getting through 4Hi and 2/4Lo engagements. In my own little mind, the ultimate version of 2/4Lo would be a direct engagement that could at least bypass the wait for 4Hi and the speed limitation raised to about 10mph or just removed altogether, accepting the known risks there.

I am absolutely stoked to do this. Do you have a recommendation for a terminal crimp tool? I have some 20ga MS wire. Is that in the range for this?

 

Haha! Sorry, but I didn't even download it. The OEM one getting stowed in the OM case was my very first mod. I think I did that before the Taco even got to my driveway.

 

It definitely possible that you could do a transfer case overrride mod, and force it into 4Lo while telling the computer it was still in 2Hi. With the front ADD still free you would get 2Lo that way. I could probably draw up a schematic for it, but I dont know if it would work until testing it. But there would be no speed lockout without a pretty advanced solution with a raspberry pi or maybe arduino or something.

I used all 20awg for mine. I try not to go any smaller than that, its a nice compromise on not too weak to be delicate and being too stiff I think, and will carry 10 amp on overload just fine. I use a relatively cheap ratcheting crimper, (don't remember the manufacturer but similar to)

$20 TITAN 11477 Ratcheting Wire Terminal Crimper Tool for Insulated Terminals, Fixed Jaw Crimper

https://www.amazon.com/Titan-Tools-11477-Ratcheting-Terminal/dp/B0069TRKJ0/
But I think its totally worth it to pay for high quality crimps. There are a few better brands (that are similar to arguing about Sport vs OR) but I usually use TE, Molex, Amp and always use digikey for this kind of thing (select first class postage). Ring and 1/4 faston connectors here:
https://www.digikey.com/catalog/en/partgroup/faston-pidg-series/9886
https://www.digikey.com/catalog/en/partgroup/pidg-series/10003

They connectors are a bit bulky and need some heat shrink to protect, but I used all 1/4 faston for the splice into the truck ECU wiring and ring connectors to tie into the relay. If I ever want to remove the mod, the faston blade connectors can be reattached male to female to return back close to original Blueprint.

 

Thanks for the recommendations. I've seen A&Ps do some fast, quality work with good crimpers like that. I've been getting by with pliers, then solder, and heat shrink. A solid connection, esp in an application like this, would be key. I want this to work permanently.

 

Forgot to mention. I recommend to always test your crimper/terminal/wire combination on the bench before you begin on a piece of wire and sacrifice a terminal. Obviously can't do that on actual truck harness. That lets you section the terminal to inspect the crimp, strip off the insulation from the terminal to check the crimp, and at a minimum put about 10 lb tension test on it if using 20 awg wire to check for excessive or insufficient crimp. If it passes that load, it is a crimp you can be pretty confident in. But I think you will find that better quality terminals are the most important factor, especially as they are made with serrations or dimples that increase local pressure on the wire in a controlled way, that the cheap terminals lack.
http://media.digikey.com/PDF/Data Sheets/Molex PDFs/TBO Quality Crimp Handbook.pdf

 

Good point.

I do give mine a nice pull and had them slip out in the past with cheap terminals using pliers. That is why I went to crimping and soldering. I'm looking forward to not doing that with the bits you recommended.

 

I like this Idea as I have a MT and reverse is just stupid high. But, I noticed this in the PDF..."Don’t do this mod if you off-road remotely by yourself, as it increases the failure modes of the 4 Wheel System." Could you elaborate on this for me?