Running a Posi & R&P Selection

[Maxacceleration]

Hello all,
EVERYBODY here seems to talk lockers all the time. I have had amazing results with posi units in the past. On a Toyota and a couple of Fords'. Its a unit that works seamlessly and quietly. Change the oil and additive every 30K miles...
I believe one is available for the 470 8" rear end? I think a posi should have good results. I am not a rock crawler and hopping up stair steps, plus I always engage 4x4 early so as not to spin tire.
A posi will not spin where a locker will. As in tight hairpin corners. Its easier on the vehicle than a locker on the street.
They hook up.
Whats the consensus?

Now have I seen R&P gears in 4.10, 4.30, 4.56 & 4.88 for our GX470?? Is that correct?
My local shop says 4.56 will be a good match with 33's, keeping about 2300 rpm @70.
Sound about right? TIA

 

[rommelrommel]

If you're using your locker on the street you're big dumb. I figure if you're going to spend the money the locker is better.

 

[jiggletits]

No one does a full time locker except morons and dedicated off road rigs that get trailered IMO. What Everyone does do is selectable E-lockers because it doesn't make sense to do anything else on an AWD vehicle with ATRAC... you effectively already have LSD/posi, whatever you want to call it, from the factory.

The e-locker disengages when you don't want to use it. I have them front and rear on my Tundra and have one waiting to go in on the GX but only for the rear. They have gotten me out of some pickles quite easily. Tundra sees 90% pavement. I only have lockers when I want them.

 

[BigSunnyD]

Newb chiming in here and too lazy right now to use the search function. I think the OP meant to ask what E-locker is best......

 

[Maxacceleration]

If you're using your locker on the street you're big dumb. I figure if you're going to spend the money the locker is better.

Huh? I did not call you anything. I'll bypass that immature statement.
If tires are in the air a locker is better IMO, otherwise a posi is a very good unit with good clutching action. Of course a locker clutches to a point.
To me locker is over rated for a non dedicated off road rig, which a Lexus is not. A posi in the rear of my vehicle will be wonderful.
Anyway, I have my appt for gear & traction aid. Thank you

 

[Maxacceleration]

Oh, will a posi unit get in the way of the Lexus ATRAC system? I mean I see selectable lockers used on the Lexus. Why not a posi?
Trying to learn some here...

 

[jiggletits]

I'll spell it out again in simpler terms;

ATRAC works just like a posi/lsd but instead of transferring drive power, it limits wheel slippage through the ABS system. Installing a posi or lsd is a waste of money and yes it will render ATRAC mostly useless because you'll now have two systems doing the same thing.

A selectable e-locker is only engaged when you want it to be. Best of both worlds; fully locked with the press of a button. Fully open the rest of the time with no change to driving characteristics.

 

[Maxacceleration]

I'm following jiggle. With that said, maybe a re-gear will be all I need. Does the ATRAC cut power when wheelspin is detected? Like what has been known to happen on ice?
Can I only rip a slide (wheelspin) when the center diff is locked?

 

[jiggletits]

You really don't need a re-gear for 33s either. Stock tires are ~31 and this motor has gobs of torque. 265/70/17 is the best tire IMO. 33's require a bunch of bull**** to get them to fit without rubbing.

As I understand ATRAC does not cut power but VSC does.

If you're wanting to "rip a slide" you should probably buy a camaro.

 

[BigSunnyD]

Jiggles, you got a recommendation for a locker?

 

[Maxacceleration]

Ok Jiggles.
So for debate... Even V-8 vehicles re-gear (or should) when going to larger tires. To me this would be true for the Lexus.
I hear you on tire size. I happen to be going farhter than most with an extensive upgraded suspension. Turns out to be 3"/2" added height.
I am also doing the pinch weld & BMC. Changing out fenders & bumper also. So quite a change coming up...
Thanks for enlightening me on the factory traction aids. I never thought how a posi unit would interfere with it.
Am I also understanding correctly the traction aids are off when the center lock is engaged?

 

[Maxacceleration]

Another analogy might be, loose soft sand, or mud where momentum is key. Gotta keep it nailed which may mean wheelspin.
Is that when the center diff lock is to be used so some wheelspin can be had vs traction control cutting power?

 

[jiggletits]

I recommend the Eaton e locker. ARB sells air lockers but those are a hassle, can leak and not work, cost more up front plus you have to buy compressor.

If you insist on regearing, you really don’t need to for 33s, then you might as well get a front locker too.

Just differentials has the Eaton for like $1080 shipped with their discount code.

FWIW the Nitro rebuild kit contains authentic Koyo bearings. I’d recommendd providing that to your shop so you don’t end up with some cheap s*** from auto zone.

 

[Rednexus]

I would go to your preferred tire size/lift, wheel for a bit, and see if you really need a locker. I have 32" tires and a 2" lift, when aired down to 15 psi, the GX will go a ton of places using ATRAC, including mud, rocks, and snow. ATRAC does have some limitations as it's a reactive system, but it's worked pretty well for me in a lot of different environments. I would eventually like to do lockers, but it's pretty far down the mod list at this time.

In a GX ATRAC is only active in 4LO and cannot be turned off. I did have an issue where I got stuck in a deep mudhole when not aired down, as the ATRAC would clamp down the breaks and slow the GX down as I was trying to get out. Since then I've always aired down off-road and have been through a number of deep mudholes with no issue - and can feel ATRAC clamping down on various wheels to help pull through.

 

[Maxacceleration]

Good thoughts Jiggles, thank you. I have the Eaton E locker planned for the front. ...Posi for the rear... I'll back out of the posi unit and see if I can swing two E lockers. The prices are kicking my butt.

 

[Maxacceleration]

Thanks Rednexus, good info.
My thoughts have been... low(er) gearing and old school traction aids. To make a vehicle run easier on tough terrain... I am trying to come up to speed on the electronic aids built into the modern vehicle - even if it is 18 years old. lol
Most everything I have ever modded has been pre traction control...
I will talk with my well established rear end shop tomorrow (Randys R&P)!

 

[Maxacceleration]

I keep coming with counter points.. Don't shoot me - I am just trying to educate myself as I always try to do.
Back to a rear posi/lsd unit... I am not sure how it would interfere. If the posi unit is always maintaining traction as a posi unit does, wouldn't it work in conjunction with the factory traction control? If the posi unit doesn't allow slip here or there, the traction control wouldn't not have to activate and grab brakes here & there?
Would a posi upset the system in icy roads conditions? Seems traction could be kept longer before tc has to come to the rescue??
Just trying to educate myself & others maybe - thank you.

 

[rommelrommel]

Huh? I did not call you anything. I'll bypass that immature statement.
If tires are in the air a locker is better IMO, otherwise a posi is a very good unit with good clutching action. Of course a locker clutches to a point.
To me locker is over rated for a non dedicated off road rig, which a Lexus is not. A posi in the rear of my vehicle will be wonderful.
Anyway, I have my appt for gear & traction aid. Thank you

Umm, you didn't say you were using a e-locker on the street so it wasn't directed at you.

If you're going to spend money on regear and posi, why not spend the money on regear and a e/air locker? As pointed out the posi doesn't do much different than the traction control/atrac already does. This truck simply won't break traction much on the street anyways with the center diff splitting torque. If you think you need/want a front e-locker I would really lean towards an e-locker in the back. Between the VSC/Atrac/etc wheelspin isn't really a big problem until you're articulated far enough to need a full locker, and then the posi probably won't get it done.

 

[Jstawgn]

Would a posi upset the system in icy roads conditions? Seems traction could be kept longer before tc has to come to the rescue??
Just trying to educate myself & others maybe - thank you.

A clutch type would be impacted stability control on ice. A torsen type a bit less.
Ice racers always use open diff for this reason.

I have elocker and one time I activate it accidentally on snowy road. The stability control does not even try to correct anything. I just spin and do 360. VSC got confused and cannot brake one side to correct the slide. Needless to say i put a secondary switch to make sure it only activated when needed.

 

[VSPro9]

I keep coming with counter points.. Don't shoot me - I am just trying to educate myself as I always try to do.
Back to a rear posi/lsd unit... I am not sure how it would interfere. If the posi unit is always maintaining traction as a posi unit does, wouldn't it work in conjunction with the factory traction control? If the posi unit doesn't allow slip here or there, the traction control wouldn't not have to activate and grab brakes here & there?
Would a posi upset the system in icy roads conditions? Seems traction could be kept longer before tc has to come to the rescue??
Just trying to educate myself & others maybe - thank you.

i believe you are correct here, a-trac kicks in when it detects wheelspeed differences at a low, steady rpm i believe in 4low only but may be wrong. if youre LSD is activating before a-trac, then a-trac wont hit, if your a-trac is activating before your lsd, then your lsd wont hit.

Edit: i may be wrong on this but while we are discussing atrac, is it true that it wont kick in when you have your check engine lights on? p0430 for my downstream 02 sensor is always on and that lights up my CEL and the vsc trac, vsc off, and car with slippery tracks light.