The AWD Tacoma Mod - Swapping in the 3rd Gen 4Runner T-case

It’s alive

 

Totally doable, just means your wiring work is much more extensive than mine. Feel free to post any questions here as you get into it.

Sure... anyone want to donate a vehicle for R&D?

You're right! I've added some updates to my first post.

 

Now that you accomplished this amazing feat, I challenge you to retrofit a 4runner/Celica directional stalk with the fog light rotary like in this thread:

https://www.tacomaworld.com/threads...-headlight-switch-stalk.471193/#post-14208866

 

What resources did you use to find the pinouts and connectors for the 4wd controller? I may end up making my own harness if I cant find one.

 

I used the factory service manuals for both the Tacoma and the 4Runner. The wiring diagrams show the circuits and pins for almost everything in the vehicle. Use this link at your own risk: http://web.archive.org/web/20110102225436/http://www.ncttora.com/FSM/

 

Wow, that's cool. So your Multimode is the one that is completely manual? Meaning your shifter is like this?

 

Yes, that’s the shifter I have, however, it’s not manual like you are thinking. The 2-4 shift only activates a switch on the side of the tcase. The ECU detects the switch state change and commands the shift motor to turn to the proper position. This is needed because the ECU strategy is to lock the tcase first. Then once the components are up to speed the center diff is unlocked. Make since?

 

You set a high bar, well played sir!

Had been considering the same swap, couldn't ask for a more detailed or well presented write up.

top notch work all around

 

Great write up! That was a fun read. Thanks for putting so much effort in, that’s what makes TW great.

 

Wild guess.

Is that 93 as you're coming into Marshall/So Boulder?

btw - that video is hilarious.

 

in the early 2000s mini truck days i seen a couple guys add awd to slammed 5 lug street trucks using these t cases. had custom front suspension setups to go with.

 

Thank you!

This was heading south from Steamboat on US-40

 

Now I'm definitely curious whether the Multi-mode system is purely an archaic mechanical form of a center diff that has no countermeasures for slip. As you mentioned earlier the pitfalls of an unlocked center diff without engineering aids is a total loss of forward momentum if one wheel slips regardless of what axle its on. Power is sent through the path of least resistance leaving you one wheel peeling in "AWD".

I'd be surprised if there weren't some additional measures as even early 80 series LCs added a viscous coupling for their Full-Time 4WD after a couple years of its release; around 92' or 93' something like that. I glanced through the transfer-case exploded diagrams and found nothing relating to a viscous coupling, multiplate clutches or wet clutch packs. It seems like just a simple planetary gear center diff set within the T-case. Curious if their is some electronic wizardry going on here to prevent a one-wheel-peel spin out in AWD.

It's funny though because it sounds like its a 50:50 symmetrical power distribution in the AWD 4H setting but using a planetary gear set for the center differential is usually done when you want an asymmetrical power distribution by reducing the planet gear size a certain ratio comparatively to the sun gear. Otherwise a normal pinion bevel gear center diff system is preferred for the 50:50 setup. Am I missing something? Awesome writeup by the way, going to have to designate some real time going through this in depth.

 

How hard would it be to do this in a 2000 tacoma prerunner 2.7

 

Sorry, I don’t know enough about the 2.7L model to give you a good answer. I would assume since you don’t have 4WD to begin with you’ll have to make your own harness or swap in a harness from a 4WD truck.

 

I've never done this work so don't take my word for absolute truth, but here's my best guess based on what I've read here on TW.

I can say with some confidence that it won't be easy. There's lots of good info you can use in this thread and in others, but there's no complete instruction manual for your case. You'll have to do some figuring out, and your truck will likely be out of commission for a while. If you make it work, take lots of good notes and pictures for the rest of us.

Since it's a Prerunner, you'll for sure have to do all the standard 4x4 conversion stuff, which is already well-documented on this site. Usually the 4x4 conversions use locking hubs and a j-shift transfer case to avoid having to mess with electronics.

The multi-mode transfer case will require some amount of electrical work to control the center diff lockout actuator--either wiring up a custom circuit or retrofitting an entire 4x4 control module and associated wiring harness. I have no idea how difficult this would be, and can only recommend studying the 4Runner and Tacoma electrical wiring diagrams to learn how things worked from the factory.

That might be the extent of it. There is some info around the forums about 2.7L trucks using 26-spline shaft between the trans and t-case while 3.4L trucks use a 29-spline shaft, but I think that only applies to the manual trans (w59). If you stick to an auto you might avoid that issue (again, not 100% sure--do your own research to verify). If you're also planning to manual swap, you'll need to swap the input shaft in your t-case to match the trans.

 

So, uh, what do you charge for this upgrade?

 

As much as I’d rather do Toyota Upgrade R&D full time, I suspect the amount of people that would actually pay for this is rather small.

 

How have you been liking it up till now? Had it on any of those icy/snow/wet roads where it would be most beneficial?

I have been thinking of doing this for a while, as I think it would be awesome to have AWD for those main logging roads where I don't necessarily always want locked 4W9, & especially since I’ve been on some trips in those bad conditions on the highway, and boy did I miss not having my Subarus AWD for that. This seems like a very good mix of them both but in a Taco!
Also it was very nice to see a well detailed write up! Thanks