00' 2wd Tundra with 02' Sequoia AWD Swap

Over the summer my rear-end went bad causing my transmission to lose functionality. As a former Toyota tech, I decided it would be worth my time to rebuild the trans rather than swap in a new one because it has never had problems before and has 260k miles. While having the transmission out I decided to go ahead and do a 4wd swap I've been planning for a few years. This was beneficial because when I was swapping the output shaft housing I discovered more issues with the trans that was causing problems. While rebuilding the trans I swapped over the A340F output shaft and rear housing, I already had the larger 4wd oil pan on my factory A340E. I chose the 1st gen sequoia transfer case due to its versatility across all conditions vs a standard 4wd transfer case like what came stock in the Tundra or one from an FJ. The only issue now is the wiring. I have the 4wd ECU that would've come with my truck given it was 4wd, the ECU from the donor Sequoia, and one from a later 1st gen Sequoia.

Parts Installed:
-Transmission output shaft and housing (from 01' Sequoia A340F)
-4wd transmission brace (from 01' Sequoia)
-01' Sequoia transfer case, $54
-Tundra 4wd ECU and transfer case wire harness (later replaced with 04' Sequoia 4wd ECU), $15
-4wd/ 4lo dash buttons
-01' Sequoia front drive shaft (needed for the extra length between front diff and transfer case)
-Front diff with ADD (4.10 gears) from 01' Sequoia, $45
-4wd spindles/ hubs (99' 4runner, $60) and new Tundra CV axles
-Custom rear driveshaft (3" shorter than Tundra 4wd driveshaft due to the extra length of the Sequoia transfer case, Sequoia rear driveshaft was 1 piece and too short), $450
-4.10 rear gears to match front diff (from 01' Sequoia), $99

After looking at the schematics of the Tundra and Sequoia 4wd ECU I thought the wiring would be simple as most of the connections are the same. Where I ran into trouble was the transfer case actuator motor positions for the Sequoia, H4F-H4L-H2, which don't match the Tundra, H2-H4-L4. I have looked for anyone else doing a swap with a similar transfer case and I cannot find anything out there, most people doing a 4wd swap on this generation truck use a 4runner or FJ case.

Can anyone point me to information on how to get the Sequoia transfer case to work with the Tundra 4wd ECU or how I can wire the Sequoia 4wd ECU to work with my truck?

 

Here are the 4wd Ecu diagrams for reference.

 

Not sure if it helps, but scroll to the 4th/5th paragraph of this thread: https://www.tundras.com/threads/so-you-wanna-buy-just-bought-a-1st-gen-tundra-eh.115928/

Note the series of links there, including links to FSM, electrical diagrams, and other stuff which may be of help.

Sadly, that's the best I can do, you're in at a far deeper level than I am, and you likely hae way more knowledge inbetween those ears on your head than I do on mine.

 

After spending some time this week I have come up with a wiring diagram that I think will work using the 03’-05’ sequoia 4wd ECU.

I spent some time last night getting the extra wires crimped and ready to install tonight, will post an update when it’s installed.

Edit: In the diagram I show that a W/R wire should be connected to pin 16 and 17 of the 4wd ECU, this is wrong. No need to make a splice for a second pin as the wire should be plugged into only pin 17. I figured this out after I started having a p1780 code that would randomly appear, PNSW fault that I could not trace back to the PNSW. So far this has eliminated the check engine light, and the AWD is still functional.

 

After hours upside down in the passenger foot well repining connector IE2 the AWD swap is compete. My updated schematic works flawlessly with the factory, 4wd buttons and dash lights. The only change would be to make the 2hi/4hi button non-latching as the signal the ECU requires is not constant power.

When I was originally diagnosing the problem, I did not notice that I had IE2 pin 12 (green, power to transfer case motor) in the correct place. I found it resting in pin 14 of the connector, must’ve been a long night when I was putting that in. As soon as I switched the wire to the right pin location, the Sequoia ECU worked, I wonder if it would’ve worked on the tundra ECU if I had a found the issue earlier.

Next step is to scratch off the 4lo silk screen and add a diff-lock sticker to the button, as 4lo is now controlled by the shift lever.
Edit: I forgot that the buttons have lights behind them and the labels are molded into the button not painted on.

 

I thought a 4wd swap would be way too much work to be worth it but maybe I'll reconsider with some help on the wiring for 06 vvti.

Did you have a donor truck to swap everything over from?

 

Sounds like a cool swap. I've actually wished my Tundra had the AWD tcase a few times. I took a new job last year that has had me driving nearly 500 miles round trip almost every week, driving from Southern Utah to Northern Utah. Last winter was absolutely bonkers here and drove up and back in gnarly ice or snow storms almost every week all winter. Tried running in 2wd as much as possible... until I lost control and 180'd at one point. Luckily was on a small highway, low speed, and flat shoulder, and no other traffic at the time. Just drove 4wd from then on out if the roads had any bit of anything on them.

I grew up in rear wheel drive cars in the snow so I know how drive in them, but I've also long been also driving GX470s and LX470s and boy do they drive so nice with their full-time 4wd. I think their torsen tcase is similar enough to what AWD in the Sequoia is? Anyway, it def makes me think that Sequoia case is gonna be sweet in the Tundra, especially if you drive multiple types of terrain on the regular (street, dirt, snow, sand etc). I wish my Tundra had the option.

Now, where's the pics???

 

Ohh man, I didn't know the 1st gen Tundras only came with a locked center while in 4WD. Being in a state with a real winter, the "AWD" transfer case of my 1st gen Sequoia was one of its biggest selling features.

For the 1st gen Sequoia everything with the 4 speed transmission (01-04) has an open center diff in the transfer case. Everything with the 5 speed transmission (05-07) has a torsen center diff in the transfer case.

I wonder how hard it would be to put a sequoia t-case in a 4x4 Tundra...

 

well, huh...now i kinda wished i would had grabbed the rest of the parts off the 2001 Sequoia that was at the wrecking yard a few months back...t-case, 4wd ecu, wires, dash, drive lines, cv’s, ect. Especially since the junk yard was having a 75% off sale. I’m glad i at least i bought the front diff and rear 3rd..at $26 for each end.

 

All parts came off a 2001 Sequoia in a junkyard, except the 2004 ECU. Swaps on these trucks is way easier than you would think since most of the parts share the same bolt patterns and dimensions. Electrical is where it gets tricky.

 

I'll have the truck on a lift in the next month and will take some photos of it all. Might do a dedicated install thread and talk about the theory behind how I wired it up.

 

Bump....

 

Do you have the spot to add a factory center diff lock button?
This is on my '04 Sequoia

 

Very cool swap, Paxmanhp, thanks for sharing.

I've been collecting parts to make my 4x4 Tundra into a multi-mode truck. I have a torsen transfer case and shift computer from a Sequoia and tore up some v8 4runner wiring to build a harness. This setup is a little more complicated as the transfer case actuator has 2 shafts w/ 2 motors: 2WD-4WD-AWD & High-Low. Where I got stuck was the truck's latching 4Hi button. I got the switch panel out of a Sequoia too but all the plastic bits between the 4WD controls and the HVAC are too different to graft together.

So, did you find that constant power to the 2hi/4hi circuit of the Sequoia shift computer worked fine?

 

Subscribed.

I really miss the AWD (unlocked center diff) function I had in my 3rd Gen 4Runner with the Multi-mode transfer case. Would love to have it on my Tundra.

Looking forward to more info.

 

It worked fine with the latching switch even if I left the switch “On”, you just have to press it twice as much to change modes, hence a non latching switch like the diff lock or factory 4lo switch gets used for those functions.

 

Here are the pictures of the truck in the air. The only issue I had when installing was clearance between the exhaust and transfer case. I got it to fit without removing the exhaust but I would recommend removing it.

 

Yes, kinda. My buttons are in the same spot but the buttons shapes are slightly different so I wasn’t able to use the sequoia ones that you showed. Mine are the facroy 4wd buttons, 2h/4h and 4lo, that I swapped into my dash. 2h/4h works as the 4wd button and 4lo is the diff lock button.

 

That's beautiful!

 

Here are some pictures of the 4wd ECU mounted to the truck. Since the Sequoia ECU should be mounted behind the dash the bracket would not work with the tundra 4wd ECU location and stud. I flattened out the sequoia ECU bracket so that I could bend it into a position that would bolt to the stud and fit behind the blower motor.

I also added a picture of the ECU part number for reference.