Another Path to 4WD

Hi All! First post and I'm going to jump right in!

I've lurked and searched for about a week regarding performing a 4WD conversion on multiple sites. Other than one gentleman who documented his 4WD conversion on the 1st gen Tundra, there is no conversion information found for the 2nd Generation (or 3rd). Most responses are the variety of "Sell your truck, and buy a 4WD". "You will lose the value, damage the truck, not do it right." Etcetera. So I expect a few of those responses will be here.

I do like my Tundra. It is not my daily. I use it right now only when I need to haul stuff, which isn't very often. In the last 6 months, I've maybe put 1000 miles on it. It is sitting in the garage, and I'll start it just to move it out when I need to do work on one of the other cars. It's a 2010 Limited with over 203,659 miles. I don't know any more on it than that because the ODO stopped working, but it is a good looking and running truck with all the bells and whistles I've ever had in a truck.

So here's the alternate path:

I've started to build a 4x4 parts list in excel. The major items "seem" to be easy to capture (front diff, actuator, cv axles, front drive shaft, transfer case, 4WD transmission, transfer case, shorter rear drive shaft, harnesses, etc.). The thing that concerns me is compatibility ... so, what if instead I buy a salvaged 4WD (doesn't run or whatever), but is 4WD. These can seem to go for 3500-4500. My parts list even used exceeds that. Then that way, I'll have all the miscellaneous components to switch over to my Tundy, and voila, 4WD. Dealerships said they can reflash the ECU, so even if I have to use the 4WD drive one, I think this "should" work. Aside from my time, and no lost mobility on a vehicle that I don't drive often, what are the concerns with this plan that you can think of?

Why 4WD? I'd like to overland the vehicle, moderately. It is paid off of course, so I don't owe anything on the vehicle other than maintenance and insurance (which is cheap). Hopefully this takes us down a different path.

 

https://www.tundras.com/threads/2016-tundra-cabin-swap-issues.110691/

It would be like this but harder.

 

Guess I'll sell the damn thing.

 

Might be easier to buy an aftermarket transfer case and build out from there. Make a custom adapter to mate it to the transmission. Get the OEM front diff. Get custom length drive shafts. You wouldn’t have to mess with the electronics.

 

Honestly there are lots of places to go and explore with 2wd. Maybe a rear locker and some rims that allow for strap on traction blocks could get you out of a mess. The key is to have a gap between the inner rim and the brakes to allow clearance for the strap. Strap up before you get in the mud or sand. Then of course there is the shovel, winch, hi lift, blocks, anchors or buried spare tire, etc. Just saying all is not lost just because you have a 4x2. Often 4x4 gets people in places it doesn't get them out of. Wouldn't cost a fortune to conduct some experiments and see what you can get by with. You might be surprised.

 

Yup

 

That's the first time I heard this recommended as an option. Most would suggest SAS, and if that were the only option - I would have just given up on it. Thanks for this suggestion, I'll do some research on it.

 

For sure. I watched some overlanding 4x2 videos, and while it could be seemingly capable, doing some "moderate" climbs is what interested me. I would just hate to start building on my truck somewhat, figure that the limitation wasn't something I could live with for that aspect, and then end up selling it anyways. But you make a great point.

 

I say go for it!

Like I commented on your Facebook post the wiring would be one of the harder parts. I will help here as much as I can. It can be done.

Your odometer quit working? Does the speedo still work? First I have heard of a broken ODO.

One thing that might be the deciding factor for me would be mounting locations/holes in the factory frame. If all frames are made for 4x4 and you can just bolt the transfer case in then yea. However I don’t want to have to add/drill holes in the frame or crossmembers to be able to mount/secure parts

 

Did I make a Facebook post somewhere? I must have done this inadvertently, I just checked my home page and I have nothing there. Sorry, I'm not sure where I may have linked a post from here to there from.

Yes, I actually bought it that way. The previous owner told me nothing of the odometer. It just stays stuck at 203659. Trip and speedo work fine. It's the only thing on the truck that doesn't work.

I actually think what Cruzer suggested may be the easier option. I don't care if it is Toyota integrated. But if I can push a switch for low, high, and 2 wheel drive with some custom wiring, that might be the easiest way to go. I haven't had a chance to research that option yet as I didn't consider that as an idea and hadn't seen it mentioned elsewhere yet..

 

Oh wow you are right sorry. A guy in the regular cab Facebook group asked a similar question 2 weeks ago. I assumed you and him were the same but I just looked, his name was Matt.

I want my stuff to be as factory as possible so I would be going Toyota parts all the way.

Only reason I have ever seen an Odo freeze like that is someone tried to change or update the milage. Do it wrong it will freeze. If the trip meter is working the Odometer should be also.


Here is the Facebook post I was referring too.

 

No worries. It sounds like you know Tundra wiring. So on the same transfer case thought ... the transfer case on 2nd gen tundras are electrically actuated right? I think that the transfer case from the 4WD trans mates up to the 4x2 transmission. Ignoring the other signals, couldn't the signals to the harness be spliced and sent voltage, current, relay signals etc. to manually move the selector for the transfer case thereby providing the torque to the front? This way the gear ratios would match up (just may need to get the 4WD rear differential). Thoughts and/or do you have the schematic for the wiring to the transfer case?

 

Transmission tail shafts and driveshafts are different. The 4x4 has a much different shorter tail shaft. Not sure if you can remove the 2wd tail shaft and be able to bolt on the transfer case. Doubtful as the main shaft in the trans between the two is different lengths.

The 4x4 trucks have an entire ecu that controls the transfer case and actuators. It ties into the main harness and links to the Engine ECU and other things.

 

This is the wiring for the 4x4 control ECU on a 2007 to give you an idea.

 

I'm with you ... I would need to get a different tail shaft and front shaft for any method that I use whether its incorporating the 4WD Toyota components, custom transfer case, or if we could just bolt the 4WD transfer case to the 2WD transmission, the distance "should" be a factory distance for my short bed to the differential. I feel like that is the easier problem to solve.

If I understand the transfer case right, it has 3 dentented positions. Neutral (2WD), 4W High, 4W Low which are all mechanically controlled by the electrical actuator. The transfer case is dumb to the input shaft of the transmission other than those 3 positions, I thought.

 

Transmission photos. I think both of these are from a 2017 ish truck but it gives you an idea of the differences.

These almost look to be the same length just much different tails and bodies.

4x4

4x2

 

10-4. You know your stuff.

 

I like the idea of a 4WD donor, if you can find one that's been written off from mid-section t-bone damage even better. That would minimize stuff getting bent and give you a replacement engine as my main concern would be how many miles the truck has done since the clock stopped working - usually there's reason for tampering with clocks and if someone has stopped it at 200k it's probably because they wanted to put a huge amount of miles on it a couple of years before selling and no-one stumps up good money for a truck with 500k on it.

 

There is another option... upgrade other things. Bigger AT tires (37s are pretty awesome IMO), small lift and suspension upgrade, and 5.29 gear and a rear locker. Perfect for overlanding.

 

I have a front diff part in south/central Texas... If you ever needed...
Came out my 2012, the extension mounting part is broken and need some seals, but gears were great when pulled.

 

I suggest you buy a subscription to Toyota TIS and take your VIN and that of donor VIN with same cab features and for example do a where used on the various parts and assault this via PN, but ya buying a tip over something like that and just plan on gutting the cab to get it done. Start there as the nuts and bolts part is pretty straight forward.

This won't win any votes, but one could do a brute strength option and run the t-case and front axle with a couple of switches using the limit switches to trigger indicator lights so you know the actual status. In and out is not exactly rocket science. Hell, we used to get out and lock hubs on the Dana-60 and heave a big lever on floor and Walla - 4WD... lol

 

To the OP, did you ever finish the conversion?

I'm currently doing this exact same thing, and had the same idea as you. I bought a "rotten frame" 2008 limited and I'm in the process of converting my 2015 SR to 4wd. The added bonus is I upgraded my interior to Limited trim.

I'm adding the following facts, in case someone else comes across this post with the same intention.

ECU, the original 2WD ecu will play with the 4WD controller once all the wiring is in place (if you look for the P/N of a 2WD and a 4WD you will find the same PN). Toyota made a beautiful thing with the CAN bus and everything is Plug and Play.

Transmission: the only difference between the 2WD and the 4WD trannies is the output shaft and the extension housing, both are swappable but the output shaft requires you to gut the transmission. If it's old may as well get it rebuilt in the process.

Wiring:
4WD selector switch in the dash: only two wires need to be connected to the 4WD controller, I wanted a factory look so I bought the trim piece and the 2.5 gen selector knob but the 2.0 gen would work with a little DIY mounting.
4WD controller to transfer case and to ADD wiring. Taking all wiring from the donor truck but had to cut it under the truck as the wiring is part of the main ecu engine harness. I did not want to trace each wire to the origin. I bought automotive connectors on Amazon (different pin quantities) and I'm working on the wiring.

Mechanical. The frames are the same from 2007 to 2021, 2WD and 4WD are all the same. Everything is bolt on. The only thing I still have not been able to remove is the rear mount of the front ADD, it's rust-welded so I may have to buy one. Broke a breaker bar taking it off last time I tried but I'll try again this weekend.

I am rebuilding the donors CV joints and got new wheel hubs (4x4 model) to install on the existing steering knuckles (also shared part, just need to pop out the rear cover). Will need new seals throughout.
I bought 4.88 gears for front and rear since I already installed the 20" Limited wheels and they came with 35" mismatched tires. Will do tires later, I've been driving with positive camber, product of my shocks installation and have not wanted to do an alignment until I get the ADD installed. I put Bilstein 5100s all around, front on the top mount so I got around 2.8" of lift and replaced the front bumper with a steel one and got an Amazon 13K winch in it. No rubbing and looks mean.

Will document everything in a new post and a video too.

 

Mehnock,

Is there a difference between the 2wd and 4wd transmission wire harnesses? I was hoping that Toyota had the same harnesses for both versions of the factory. If that is not the case, could you please explain (like I'm five) how did you wire the controller into original harness.

Cheers

 

I believe they are the same. I have my conversion on hold as I moved to Costa Rica from Fort Lauderdale (brought my truck and all the parts for the conversion) and I'm working on remodeling a house we bought. I hope to be able to get back to it soon as I really need it now!

The controller needs access to the CANBUS and the 2/4WD selector switch, then the rest of the wires go to the transfer case and the ADD.

If you are good with diagrams and wiring, it should be easy.

 

excellent work; as far as the seized mount, heat will help a ton and get some good bolt penetrant (free all or mix 1/2 acetone and atf) alternatively instead of the penetrant, heat it up and melt a crayon into the threads

 

harnesses should be the same as long as its a 2008+
to my knowledge the trucks are prewired across trims on 08 and up

 

Thank you for the information. One more thing, do I need to wire anything for the control button?

Cheers

 

If you’re referring to the 4wd selector switch I believe no, since yours is a 2011 you should be good

just pull the trim of and see if the plug is there