Running a Posi & R&P Selection

[Jstawgn]

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.

This is very true. You got check engine light and you only have brake assist.

 

[VSPro9]

This is very true. You got check engine light and you only have brake assist.
View attachment 2912010

So with the lights on as shown, even though i have only a p0430 (o2 sensor) issue i don’t have any traction aids right? (Ignore cat)

 

[Maxacceleration]

Thanks for the debate guys. I am learning my new to me used 470.
Of course everybody wants the ultimate traction at the ultimate time of traction crisis lol.
I certainly dont want to lose snow & ice traction ability. Living in the PNW, I will see snow and ice the most in a 12 month cycle.
I certainly dont want to have to go into my diffs twice if I dont have to. I am calling my diff shop now to see what their recommendations are.

 

[CO_Hunter]

I think you have gotten some good advice and I‘ll just summarize my experiences as they relate to your initial questions. For my needs/wants I went with a near 33” tire and no you do not need to do a lot of modifications (BMC for example) to fit it, read up on the many tire/wheel threads here and convince yourself that is true. Depends on the specifics of what you want to run. I swapped in an 8.2” rear end from a 2014 4Runner and re-geared to 4.56 and added an airlocker. The gears give me about +400 rpm over stock at 75 mph. Also helped with a trailer and stiff Wyoming winds at altitude. The locker/ a-trac combination has worked well for me and have not felt the need for a front locker.

Pretty impresed with the atrac. Just recently I was goofing around getting in some deep shoulder snow on a side road and got into a ditch I didn’t realize was there, so I had two wheels on snow packed road and two in the ditch leaning pretty hard. The locker with wheel spin and back and forth came close to getting me out. I decided to give it less throttle and bump it. The atrac kicked in and walked me back onto the road, rear still locked. Just one recent example for the combination you are contemplating. I drive with my VSC switch in off mode all the time.

 

[Jstawgn]

So with the lights on as shown, even though i have only a p0430 (o2 sensor) issue i don’t have any traction aids right? (Ignore cat)

View attachment 2912064

Yes, only brake assist are still working. No VSC, TRAC and ATRAC

 

[Arailt]

Posi options

Front - Eaton 913A612 - Detroit TrueTrac - Toyota 8'' TV6 Front 30 Spline (4 Pinion / V6) - https://www.drivetrainshop.com/Detroit_TrueTrac_p/eat-913a612.htm
Rear - Eaton 913A610 - Detroit TrueTrac - Toyota 8'' TV6 Rear 30 Spline (4 Pinion / V6) - https://www.drivetrainshop.com/Detroit_TrueTrac_p/eat-913a610.htm

 

[Arailt]

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.

ATRAC is not a 1:1 replacement for a mechanical LSD. You can't have fun with ATRAC. You can have a lot of fun with Posi/Mec LSD. It also won't affect on road driving like a locked diff will, other than more grip in the rain/snow. I ran trutracs in an old jeep front and rear and it was unstoppable. No need to lock/unlock. When in doubt, throttle out!

 

[Flight2k5]

Only GM used a Posi. Its just their term for a LSD

 

[Rednexus]

Would it be the best idea to run a front non-selectable LSD/locker in a full-time AWD vehicle like a GX? Seems that it would affect the steering during daily driving, relative to a normal 4x4 where 2WD can be selected and the front hubs can be unlocked. Also how would the front and rear LDS's interact with the center torsen LSD, when it is unlocked?

I plan to eventually do this mod but intend to use Harrop E-Lockers front and back. If you are already doing gears/traction aids, another $1200 for selectable Harrops vs. LSD's is not a huge difference in the overall cost.

 

[Arailt]

Only GM used a Posi. Its just their term for a LSD

Yep, kinda like Kleenex. GM won the branding war on that one.

 

[Maxacceleration]

I am at considering only the r & p change to 4.56. Thinking I will stay with the factory computer controlled traction aids.
I have been watching Logan King YT channel and his Canada snow background & wheeling with a Tacoma, Runner & FJ.
Apparently he runs (w/35's) stock gears & no aftermarket traction aids. His GX looks to run supreme in snowy, icy conditions IMO.
Thats says a lot to me.
Still I understand the benefit of correcting gearing after enlarging tires substantially. Without changing gearing, your motor is running below its optimum powerband.
It is.
The 295/70-17 I am going with are essentially 34" tires (remembering 35's are not actually 35's either). Running 4.56 will help with the feeling of over oversize tires go away mostly, and its easier on the trans/drivetrain also.
Amazingly my new to me GX came with 33x12.500 20's (!). Who 'da thunk... I will check my rpm's at 70 mph today and see where the rpm's sit now. We are calculating w/4.56 to run apprx 2300 rmp @ 70 mph.

 

[Arailt]

Would it be the best idea to run a front non-selectable LSD/locker in a full-time AWD vehicle like a GX? Seems that it would affect the steering during daily driving, relative to a normal 4x4 where 2WD can be selected and the front hubs can be unlocked. Also how would the front and rear LDS's interact with the center torsen LSD, when it is unlocked?

I plan to eventually do this mod but intend to use Harrop E-Lockers front and back. If you are already doing gears/traction aids, another $1200 for selectable Harrops vs. LSD's is not a huge difference in the overall cost.

I read you can run torsens on one or more diffs. I'm not sure about other style mechanical LSDs.

When I was living in PA, I was seriously considering the Eaton torsen style rear that I linked earlier to help with driving in the snow. Now that I'm in Texas I think I'd go for the e-locker.

 

[Maxacceleration]

With the 33x12.50-20 tires (measuring at 32") on my vehicle now it runs 1900 rpm @ 70 mph gps measured.
34" (295/70-17) tires with 4.56 gears calculate at 2300 at 70.
That is a change for the good. Even though 400 rpm's doesn't sound like much gain, it can be quite a bit of difference in how your machine performs.
...What I have noticed based on experience. 2200 @ 70 I think is about ideal. I have always over lowered and been at 2500+- @ 70
I am not the most aggressive driver doing the hardest trails, so... IF I do any additional traction aids they will be E lockers. I have 2 months to my appt to decide...
Thats all I got... Studying up!