Center Differential Lock and Electric Circuit for prerunner to 4x4 conversion

Edit: I decided to go with oem conversion with 4runner parts since this solution looks not feaseable at end, althought it help me understand how 4WD system works.
://www.tacomaworld.com/threads/prerunner-to-4x4-conversion.468300/




As part of my investigation of converting my 05 prerunner to a 4X4, I'm wondering what is the difference between 4runner transfer case and Tacomas transfer case? . 4Runners have the option of locking the center differencial, but tacomas don't.

Having a center differential lock should be usefull when you don't have front or rear lockers.

if any one knows the differences, please detail it.

 

Actually, Tacomas don't have the option of >unlocking< the center diff - because there isn't one. In 4H or 4L, you have the front and rear locked together although, of course, there are diffs in the front and in the rear.

 

Not all 4Runners have a center locking differential. Only the ones that were V8 and AWD. The reason there is a need for a center differential lock in that case is because when it's all wheel drive, it's necessary for the front and rear driveshafts to be spinning at different speeds due to different speeds between all the tires during a turn. When the center differential is locked, it's basically the same thing as a part-time transfer case that can be found in all Tacomas - where the front and rear shafts are going to be turning at the same speed when in 4wd.

Now I'm not 100% on whether that's right or not, but I've tried to understand the concept. Therefore, if someone knows how it really works, and I'm wrong, please say so!

 

I'm still cornfused by the whole center locking diff thing. My wife's '06 4x4 v6 4runner Sport has one. Would It allow all 4 corners to have power like front & rear lockers would?

 

No, it simply locks the front and rear drive shafts together. Power would be split between 1 rear wheel and 1 front wheel.

 

My wife 2006 V6 sport edition 4Runner is part time 4WD, you can selec 2H, 4H or 4L. Center differential lock can only work on 4L.

When I get down the vehicle to check out the difference between tacomas and 4runner transfer case, is no noticeable at first sight. I mean, I can't figure out where the center differential is located.

 

Cool beans. Thanks for the info

 

Then that is why Tacoma's 4x4 should only be engage on slippery surfaces...

 

Well, I'm trying to figure out a DIY circuit for the 05 transfer case without using a factory computer. First come out with a 10 relay circuit and 2 additional for the ADD.

The idea is that actuators do exactly the same a human does in a manual transfer case, like the FJ, only been really important the internal limit switches of the transfer case actuator to stop shifter once it reaches the selected position.

 

do yourself a favor.

Manual FJ case with twin sticks.... no need for computers or the actuators.

 

I wish my truck had a manual transfer case.

 

I'm kind of obsessed with coming out with a relay configuration, that can replace computer, using original 4WD selector.Maybe I will go with FJ transfer case, but I'm not close to electric actuator.
Attached you can see what I have come with, but I have to state that in no way I'm saying this is a solution since I haven't test it yet, also need to add relays for ADD and figure out connections to dash 4WD indicators.

 

Figuring out how to make ADD actuates Firts and then desconect ADD motor after engaged and then beging transfer case actuator . I can do it adding 2 more relays which i'm trying to avoid. All ideas are welcome.

 

I'd be more inclined to get the tcase into 4wd before doing add. That way the tcase can be spun by the trans get engaged then spin the front diff to engage the front.

Ie. You are stuck in 2wd , can't move forward or back and can only spin the rear tires. If you are trying to engage the add on the front first but its not lined up to mesh (which it probably isnt) you won't be able to get into 4wd. Now if in the same situation you activate the 4wd at the tcase first you can leave in in drive and spin the rears to get the tcase to engage fully, then once it's engaged the front diff can be spun to a point where the add lines up and can fully engage.

Either way good luck on the wiring !!!

 

Well, here I got the final draft for control circuit using relays. When I began figuring out this control, I initially though it was going to be more simple. The complication on using so many relays is due to H4 output, from Toyota 4WD selector, been a combination of H2 and L4 been outputted to ground at the same time. Once you see how huge the system is and how many failure modes it can has, you end up thinking of other three possibilities:
1 Doing it with a PLC or microcontroller, which won’t make more sense than second option.
2 Using original Toyota controller and wire harness
3 Going with the FJ transfer case. (Yeah I know, every thread around remarks this option, however no one that I know had justified with a diagram, why using electric actuators and original Toyota 4WD selector is a pain in the neck).

Anyway, here is the diagram, more fuses has to be added, but that is a simple task. I hope anyone having the doubt of why doing a prerunner to 4X4 conversion, using Tacoma transfer case with actuators, is kind of complicated.

(For practical applications, this control circuit hasn't been tested, use it only for reference).