It is looking like I am going to be buying a 2005 Tacoma 4x4 with the 4 cylinder and a 5 speed manual. I really like being able to use low range in my '87 4x4 with the hubs unlocked for basically 2wd low. Has anyone been able to modify their 2nd gen Tacoma to be able to use low range in 2wd?

I have done some searching, and it appears the computer looks for feedback from the differential to see if it is engaged, so that could be a problem wiring in a switch to disengage the front differential. It also looks like an FJ Cruiser transfer case can be swapped in to get a manual shifting lever, but it seems that it might only work for V6 trucks. Does anyone know if that works with the 4 Cylinder/5 speed?

 

10 sec of google netted this: http://www.tacomaworld.com/forum/1st...utton-4wd.html

seems like an easy fix and could be real clean with a switch install.

 

Isn't that just for the 1st gen Tacomas? I need to look at the truck once I get it, but I believe the setup on the 2nd gens is somewhat different.

 

doesn't an 05+ taco activate the same way - putting into 4lo activates 4wd automatically. Either way, sounds like you just need to find the correct wire and put a switch inline. Kinda the same principle to get a stock e-locker to work in 2wd/4hi instead of 4lo only.

 

That is originally what I thought, but it appears the computer needs feedback from the front differential to see if it is locked or unlocked in the newer Tacomas. I will have to try unplugging the diff and see what happens. I think without that feedback it will never engage low range. It will just flash the light on the dash and beep. It probably needs some kind of swith to fool the computer into thinking the front diff is locked without actually locking it.

If I am reading correctly, 1st gen Tacomas have either the J pattern manual shift, or a combination of push button 4x4 with a manual lever for high and low. The 2nd gen Tacomas have a knob on the dash for 2wd, 4hi, and 4lo. Basically, there is no more lever, just a knob on the dash and the computer controls the electronics.

 

I'm sure it can be done. But if you can do it, be careful. Low range might multiply the torque enough that it could break/twist the driveshaft, axle shafts, differential, etc.

The reason I say this is because I've seen older trucks with manual shift transfer cases and manual hubs that had warnings in the manual/glove box stickers, etc. against using low range in 2wd for that very reason. In 4wd, both axles take the torque, so it's less likely to happen. And I just happened to break a rear driveshaft double Cardan (CV) joint on a '78 Bronco by doing it.

 

I can see how that would be possible because there could be something like 6500 ft lbs of torque at the axles if driven hard enough in low range, and there would be a whole lot more than that in a Bronco!

 

Here:
https://www.yotatech.com/forums/f166...-right-280421/

It may "just work" as is. I picked up the parts to actually implement it just last night, and have the "unit" more or less built. Not yet tested or installed. Probably be a few more days until I get around to it.


Regarding torque;
Things generally break as a result of SHOCK, rather than just brute force. Don't do anything stupid or abusive, and it should be able to take the work. Remember that with a 4-cyl, you are starting at roughly 2/3rd the torque of the 6-cyl, and just over HALF the torque of the 6-cyl with factory supercharger -- i.e., once you factor in a margin for error, the factory assumption is that the differential can withstand well over DOUBLE the torque that the 4-cyl is giving it in HIGH range. Low range will multiply the torque by 2.54, which is **probably** still under the design limit.

The torque output also doesn't really build up until 2500 RPM, which is well above clutch engagement.

Unless you really stomp on the gas **in first gear**, and hold it there long enough for the torque to really build up, you won't be approaching the design limit. In low range, first gear will be SO SHORT, that you'd probably have to be trying to accelerate a 10k+ pound trailer up a steep hill from a dead stop.

Transmission ratios, high range;
1: 3.954
2: 2.062
3: 1.436
4: 1
5: 0.805
R: 4.22

Low range transfer case output ratios;
1: 10.04
2: 5.24
3: 3.65
4: 2.54
5: 2.04
R: 10.72

Second gear low is a pretty nice ratio for rolling trailers around.
Note that 5th gear low matches 2nd gear high pretty closely, so 5500 RPM will hit pretty close to 90 kph / 55 mph.

 

Thanks for the write-up! I will be interested to know how this works out for you when you get it installed. That looks like something I might want to try at some point.

 

Still not installed, but I have the circuit built and have run diagnostics on it. It passed all tests.
I used sockets for the relays. The sockets I got snap together into a solid block.
I am going to be riveting the relay block onto the outside of the 4wd ecu, and the actual connections all internal to the ecu rather than to the wiring harness. This makes it part of a removable component rather than part of a wiring harness that snakes through the entire vehicle.

Hmm... the_supernerd... yours is an 05, right? I just realized that that means that it doesn't have TRAC/VSC. That means that we should be able to do a simpler modification.
If you look at the schematic on my write up, you can remove relay #3 (the one that cuts the ADD wire) altogether (including the 100 ohm resistor). Keep the wire running from the diode to ADD/ECU, but do not cut the ADD wire. Just splice into it the same way as for DL2.

 

Thanks for the tip. I do not have any kind of traction control. I need to study your writeup a little better when I am fresh in the morning, but I think I am getting the general idea of how it works.

 

FYI: installed and tested and working flawlessly.

 

Thanks for the update. Glad to hear it is working. I will have to go over your write-up and see if that is something I can take on. If you ever decide to make and sell the circuit boards you might have a small demand there!