4WD and Locking Rear Diff

[pxo202]

Just got an '05 Tacoma and since this is my first ever 4x4, I am curious about the difference between 4WD HI and 4WD LO, as well as the locking rear diff that I have on the TRD Offroad Pkg. All the info I can find states that 4WD HI and LO are differentiated by the speed you use them at, but I still have no idea the inherent difference between them, on a mechanical level. Also, I understand when to use the locking rear diff but don't really understand what it is doing or why it helps to do what it does. Anyone got a spare minute to offer some insight to an eager new owner? Much appreciated!

[2tacomas]

4wd LO is for when you are in a situation where you need extra (low-range) power. You would use this when you are in a nasty situation (i.e. really deep mud) for which you will not be "flying" through at 30mph but rather need a lot of power to get you out of some really nasty stuff; in these situations you will not be going very fast because of the conditions (typically no more than 15-20mph).
You would use 4wd HI in situations where you need 4wd because of the conditions (i.e. snow on a road) but you are able to travel at a higher range of speed (hence using higher gears)- this can be used at speeds as high as 65mph (maybe even higher).

The locking rear diff. forces your back wheels to turn at the same rate, this prevents one wheel from spinning faster than the other and potentially getting you in a worse situation. (If you are using the locking rear it is probably because you are either on really loose sand or soft mud- situations in which you want both back wheels spinning at the same rate so that one does not become bogged down).
Let me know if this helps you out or if you need more info.

[greasyjeep]

the 4 lo has a differnt gear than 4 hi
so in 2wd and 4 hi the output gear is the same (final drive ratio)
In 4 lo the gear changes (you gain teeth) and reduces/icreases the ratio

so it is similar to the difference between 1st and second gear (1st = lo 2nd = hi)

This takes place in something called the transfer case
the TC sits behind the tranny and is what your drive shafts are connected to

the rear locker will cause your tires to spin at the same time, instead of one wheel sinning separately

you will want to be careful when you have the locker engaged
Only use it when you are going straight or on a surface that is slippery (wet, ice snow, loose gravel leaves.....) something that will allow one wheel to slip a little.
otherwise you will chirp tires at every turn and you can experience some odd wandering on the highway (atleast I used to when i ran a spool in the rear - same idea as a locker)

not a bad idea to engage your 4 lo once every month or so if you won;t be usein git that much
you will notice the truck seems to bog down a little and really seem sluggish, but the torque is much greater.
If you ever play tug-o-war, put it in 4 lo

have fun with the truck

[F014tomcat]

Just a quick question on this topic. when I engage my 4wd, does that automatically lock both differentials so all 4 wheels are spining at the same rate?

[Frst2FindMyTaco]

No way bro... That's the big difference between the SPORT and OFF-ROAD. With the SPORT package you get a limited slip diff which enables one wheel to pick up and start to spin if the other rear wheel is spinning freely without traction. With the OFF-ROAD package when engaging the rear locker the axle in the rear of the truck locks so both wheels are getting equal power from the truck and will only spin together in tandem. As far as 4 Wheel goes; 4 wheel drive does not necessary mean that all four wheels will provide constant drive traction. Unless a vehicle has limited slip differentials front and rear, which the SPORT only has a rear limited slip diff., it's possible that either wheel on the front and/or rear axle may lose its grip and spin while its companion just sits there doing nothing. That's the way standard differentials work. Even so, with four-wheel drive, you will always have at least one front and one rear wheel turning at all times -- which should be enough to pull you through. Just as an added note both the SPORT and OFF-ROAD do not have limited slip differentials in the front, meaning only 1 wheel traction in the front. You can always get a new differential for the front as well to give you the added bonus.

NOTE: I had a 97 Extend-Cab Taco and just bought and 05 Double Cab Off-Road ShortBed and love it.

Special Note:For all you guys out there with new 05's with rear lockers. If anyone comes across the a wiring diagram for the rear locker I'd appreciate a copy or link. As with the 95 1/2 thru 04 taco's with rear lockers within the drivers side kick panel you could pull a white wire off and harness and ground it to be able to lock the rear diff without being in 4L. I'd like to perform this function again on my new Taco but I don't want to go poking around the wiring harness without a diagram.

Well hopefully all this babble is worth it.... happy trail blazin...

[2tacomas]

I have a 2004 w/ the locking rear and I do not have to be in 4wd (hi or lo) to lock it. I just have to be at a standstill (or almost at a complete standstill) and push the rear lock button- the light blinks on my dash for a few seconds and then the rear locks. It automatically disengages when I hit about 10mph (it might be 15 mph). You shouldn't have to be in 4wd at all to have your rear lock (even on the 05). I have used the locking rear numerous times at the beach (I tend to go a little faster on sand than I should and it sometimes gets me in trouble) while I was in 2h and it locked every time- I did not have to change any wiring, it came from the factory that way.

[Frst2FindMyTaco]

I didn't know you could do that with the 04's.... and I have checked mine before.... it will not engage unless i'm in 4L

[2tacomas]

Does your manual for your 05 state that you have to be in 4wd lo to lock the rear? You can buy a Prerunner with the TRD Offroad package and it comes with a push button locking rear (and Prerunners do not have 4wd). I would think that it partially defeats the purpose of having the locking rear if you have to be in 4wd lo to engage it- a lot of people use them to get out of sticky situations w/out having to engage their 4wd. Let me know what the manual says- I hope they haven't changed it to where you have to be in 4wd lo to lock it in!!

[Frst2FindMyTaco]

Well I read the manual and it says to go to 4L to than engage rear locker but it doesn't say you must be in 4L in order for rear locker to work... Now with my 97 you had to... no if, ands or buts about it...

On another page it does state to not use the rear locker over 8 mph or for Four Wheel Drive models if you shift into the H2 or H4 mode it will disengage the rear locker for you but you should not drive around with the button depressed and the light blinking...

So that about says it... if I go to H2 or H4 I will not have rear locking capabilities...

Does your light on your dash go solid for you in H2...?

[2tacomas]

When I want to lock the rear I press the button, then the light on my dash blinks for a few seconds and then it goes solid when the rear locks- if I do not press the button again (to unlock the rear) my rear diff. automatically unlocks after a few tire revolutions or when I get to about 10mph (the light then turns off). When I get a chance I will go grab the manual out of my truck to see exactly what it says- but I know my rear locks w/out me being in 4wd lo..... whether or not it is suppose to work that way I will soon find out.

[F014tomcat]

Thanks for the info... kinda upsets me to find this out, but oh well.... it should still be enough to get me into, and out of anything...

[2tacomas]

Checked the manual on my 2004- it does say to put it into L4 and then press the rear lock button to lock the diff. I tested it out last night and mine will lock in when I am in H and L4. I know the 4wd and everything else works normal and I like being able to lock the back w/ having to put it in low so I am going to keep it that way. Hope you find a wiring diagram for you 05 so you can do the same, good luck!!