Teach me on LSD and transfer case..

Kanaljen · 07-29-08, 05:50 PM

I just bought a 2006 LC and have some Qs about diffs and transfer case.

- What type of rear diff do I have? Is it a limited slip? Is it an open diff that I can lock?

- Same questions about the front diff

- When you push that "lock" button, what exactly does it do? The manual states something about locking the center diff or transfer case.. Does it lock in the tq supplied to front and back axels? Or, does it lock the front and/or rear diff?

- Is there a difference if I change the gearing from H to L? Does it lock something even if I don't push the button?

Any drive train experts out there who can walk me through what I have and how it all works together?

Thanks!!

Trunk Monkey · 07-29-08, 06:16 PM

If you have a US spec 100, you have open diffs front and rear and a center diff in the t-case that can lock. Pressing the button with the "x" on it locks the center diff. You also have A-TRAC, which uses the ABS system as a traction device (works very well). Shifting from high range to low range you go from 1:1 to 2.48:1.

100 TD · 07-29-08, 06:43 PM

In the earlier model LCs when you selected low range with the lever, you automatically locked the centre diff as well (for low range only). For high range you selected the CDL via the push button. This created problems when you wanted low range for tight towing/reversing/boat ramps so someone posted a modification called the Pin 7 mod I think, which allowed you to select low range without the automatic lock of the transfercase. (now selectable via pushbutton as in high range).
However, in late 2003 and later vehicles I believe, the manufacturer went back to the manual lock selection via the push button for low range as well. Check yours and see if the Centre Diff Lock (CDL) light automatically comes on in the dash when you select low range. If it doesn't then try pushing the CDL switch once (best if you are moving) and see if the lamp comes on. This will then determine if you need to lmanually lock the CDL when you go to low range for off road work.

Kanaljen · 07-29-08, 10:25 PM

Thanks to both for taking the time replying!

So it seems like I have two open diffs (front and rear), which makes me a bit disappointed.. but I guess the use of the ABS system to transfer tq to wheels with traction will do..

Some follow-up Qs:
- When I lock the center diff, why does it give me better traction? If the ABS breaks the wheel with no traction and thus transfer the tq to the other wheel, why does locking the center diff make a difference?

- When locking the center diff, why does it feel like I look front and/or rear diff?? You can barely turn the car on asphalt when the center diff is locked; why is that? The inside and outer wheel should be able to spin faster even if the center diff is locked, right?

Thanks again!

ps
I don't think I lock the center diff when selecting low gearing... I think the lights are off until I select it with the buttom, even when in L.

Trunk Monkey · 07-29-08, 10:31 PM

First off - DO NOT turn tight circle on pavement with the center diff locked. Yes, each axle will be able to turn at a different rate on it's own, but the two axles together won't be able to from the t-case if the diff is locked. You can bind the differential up and damage it.

Locking the center gives you better traction by eliminating the potential for power transfer at the t-case to the axle that's slipping. So, you can think of the center diff just like the diff in an axle, except the entire front axle is one "tire" and the rear axle is the other "tire".

Kanaljen · 07-29-08, 10:39 PM

Thanks for the advice.

It make sense. if the center diff would be open all power could go to the one wheel with no traction..

But, I still can't picture it.. Why does it FEEL like the front and/or rear diffs are closed when turning?? SHouldn't the two outer wheels be able to spin faster compared to the two inner wheels, even if the center diff is locked?

Thanks,

Trunk Monkey · 07-29-08, 10:42 PM

Quote:

Originally Posted by Kanaljen

But, I still can't picture it.. Why does it FEEL like the front and/or rear diffs are closed when turning?? SHouldn't the two outer wheels be able to spin faster compared to the two inner wheels, even if the center diff is locked?

The inner and outer tires carve a different arc when turning and the front and rear axles move in a different pattern. In order for them not to you'd either have to travel a straight line or have four wheel steering.

Kanaljen · 07-29-08, 10:50 PM

Yeah.. I guess the rear outer wheel would have a shorter distance than the front..

So, how do I know for sure if my front and rear diff are open or limited?

Is there a way to throw in a LS pumking?

Would it make a big difference? The breaking of spinning wheels seems to work great but would I have better traction in sand if I had LSD front and back?

Trunk Monkey · 07-29-08, 10:55 PM

Unless you or the previous owner installed a locking differential, you're open. The 100 series in the US was only available with a factory locking diff in one of the axles (rear only) in 98 and 99. The only locking diff I know of for the 100 series is a selectable locker made by ARB.

If you just got the truck, spend some time with the A-TRAC before you mess with the diffs. You'll be very surprised.

Kanaljen · 07-29-08, 11:02 PM

Yeah, I'll be heading for Pimso sand dune next week so we'll see.

I guess I wish I could be complete locked in and truly have 4 wheel with power to the dirt.. not just 2..

It will be interesting to see how well individual wheel-braking can simulate LS...

But, if that systems would work as well as lockers or LS, people wouldn't spend the extra money on LS.

Heck, if it worked so well, why would the LC even have a lock on the center diff?

hoser · 07-29-08, 11:49 PM

Kanaljen, this article has helped many...

Diffs for dummies

It might be possible to install the LSD differential in your LC but I don't know if you'll gain much. I have one in my garage if you are interested. Only the 98-99 LX's came with LSD. I swapped mine out for an ARB locker.

Kanaljen · 07-30-08, 12:03 AM

Great link, thanks!

My Q though: If the system to individually break wheels to gain traction is so good, why even have a center diff?

What would you gain my adding front and rear lockers if the breaks increae the "traction" on spinning wheels and this send more tq to the other wheels.

Why did you change your diff? Would you diff fit my LC?

spressomon · 07-30-08, 01:00 AM

Quote:

Originally Posted by Kanaljen

Great link, thanks!

My Q though: If the system to individually break wheels to gain traction is so good, why even have a center diff?

What would you gain my adding front and rear lockers if the breaks increae the "traction" on spinning wheels and this send more tq to the other wheels.

Why did you change your diff? Would you diff fit my LC?

If say you are climbing a loose rocky hill. You get to the point that, typically, the front will lose traction first and therefore stopping your forward momentum. By locking the CDL you effectively tie the front axle speed to the rear axle speed therefore not allowing one or the other to spin separately. Try it...you'll see very quickly in this scenario what the others have explained.

ATRAC is wonderful in most situations but there are some situations, virtually always off-road, where you want to lock the diff(s) to prevent ATRAC from working. Although I do not have ATRAC on my '99 I believe, for instance, if you wanted to high rev through a mud hole ATRAC actually limits your momentum due to the way it works (a wheel slips and the brake is applied via ATRAC to counter the open differential effect). The same scenario might occur in sand...Pismo would be a fine place to test this out

.

I would love to have ATRAC and ARB lockers front and rear. ATRAC would have helped me last winter while hunting. I was traveling up a snow covered (ice underneath) off camber slope. The lockers just wanted to pull me down the slope (NOT GOOD since I was traversing a slope with a stream at the bottom that would have resulted in MAJOR winching!). But ATRAC would have allowed me to continue forward progress, more than likely, while keeping the rig on the trail since each wheel is independent. Sometimes lockers help and sometimes they have the opposite effect. Same with ATRAC.

Have fun out there!

Kanaljen · 07-30-08, 06:14 PM

Awesome info, thanks!

I'll report back after Pismo!

Topmounter · 07-30-08, 11:59 PM

A-TRAC still works on my '01 when I put it in low-range.

Kanaljen · 07-31-08, 09:40 AM

Quote:

Originally Posted by Topmounter

A-TRAC still works on my '01 when I put it in low-range.

Isn't this as it should? I haven't read anywhere that the A-TRAC is dependent on the gearing.. I'm asking becasue I'm trying to learn how this work on my new LC...

Or, should the A_TRAC be in H and the center diff locked in lower but not together?

I think I can have my center diff unlocked in L.. ie, it doesn't automatically lock so you can push the button and lock it as needed.

Is all this correctly understood? (I have a US 2006 LC)

spressomon · 07-31-08, 10:43 AM

Quote:

Originally Posted by Kanaljen

Isn't this as it should? I haven't read anywhere that the A-TRAC is dependent on the gearing.. I'm asking becasue I'm trying to learn how this work on my new LC...

Or, should the A_TRAC be in H and the center diff locked in lower but not together?

I think I can have my center diff unlocked in L.. ie, it doesn't automatically lock so you can push the button and lock it as needed.

Is all this correctly understood? (I have a US 2006 LC)

As I understand: Some of the LC's automatically engage the CDL when shifted into Low Range. Others require manually selecting the CDL button when in Low Range.

Topmounter · 07-31-08, 11:03 PM

Quote:

Originally Posted by spressomon

As I understand: Some of the LC's automatically engage the CDL when shifted into Low Range. Others require manually selecting the CDL button when in Low Range.

I only mentioned it because someone above thought it was 2003+ before the you can toggle the CDL in low-range. I remember reading somewhere that there were models of the 100 where A-TRAC was automatically deactivated when low-range was engaged.

Kanaljen · 08-01-08, 01:09 PM

Ah, that makes sense. 2003 and up should have the ability to select the CDL independently from the H and L setting.

Thanks, good stuff!

LXPearl · 08-06-08, 08:29 PM

I believe the CDL change came in 2000 with the ATRAC. I know 01 and up have the flexibility with 4LO.

The CDL locks front and rear 50:50, which does not happen with ATRAC - it is an independent wheel based system - however, in very slippery conditions, it can be overwhelmed. I had that happen this spring with a fast-falling wet snow. I was challenging the system on a winding two lane road, and when I slowed down, the ATRAC did fine. Other than that situation, the ATRAC has been a super performer in adverse conditions, including all other snow and ice conditions I have encountered. It has done better than other 4wd systems I have used from Toyota and Ford.

jhgnag · 08-06-08, 09:19 PM

Here is my understanding. My 2nd 4Runner (2005 w/the 4WD selector) felt lousy in snow, then I pushed the center lock and it felt great, just like my 1997. I think in my '03 LC ( and '05 4Runner) when the center differential is not locked, it is better than 2WD, but not as good as 4WD. My old 4Runner was better in the snow than the newer once (w/o the center lock engaged) because once you put it in 4WD, the center diff was locked. On the newer 4Runner & my LC, you need to lock the center diff to get the same traction. Yeah, the traction control helps, but if you want to get it to a 4WD vehicle, you need to lock the diff, otherwise it's All-Wheel drive.

You would never drive an older 4WD on dry pavement because of windup. Your '06 LC is the same when you have the center diff locked.

That's my take anyway!

Kanaljen · 08-06-08, 10:41 PM

Interesting info...

A few Questions:
(I have a 2006 US LC)

- If I drive in H with the center diff locked, does the A-TRACK still work?
- If I drive in L with the center locked, does the A-TRACK still work?
- Is there any difference in how I get power to the ground when I'm in H and when I'm in L? (My wife was in the sand and said that she got stuck in H and locked center diff, put it in L and could get out..)

Thanks to all!