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Been busy but finally getting back on this. The new tires have helped. Checked the axels and they were okay. Hope this helps others.
 

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I recently installed a set of Nokicin hakka R3 SUV snow/ice studless tires. On my way to my favorite ski area, just before sunlight, I was driving in ruts because the road had not been graded. It was snowing and 26 degrees with ice in the ruts. Around a corner, my Tribeca seemed to leave the ruts and slowly drift toward the ditch. Others behind me did not seem to have this problem. I slowly released the throttle and had about 25 degrees from center on the steering wheel. Finally after a couple of seconds, the car started to respond to the steering input and drive back into the ruts. I'm not sure if the rears were locked up and pushing the fronts straight, rather than following the curve of the road or the fronts were pulling to the right. I did not have the traction control off. I was using sport mode on the transmission to help going up hill. Just wanted some input on responses to to right front pull that was not intended by me. Maybe the Torsen LSD in the rear was locked up do to ice in the ruts, which then pushed the fronts straight ahead, while the road was turning left. Any ideas would be helpful.
 

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Just wondering about the center diff at 45% 55% then 50% 50% if slippage is detected have anything to do with the understeer around that corner going up hill. What ever the electronic/mechanical LSD's were doing then stopped doing and let the front tires bite, it worked. Except for the second or maybe slightly longer, I almost had to hit the brakes. That would not have a good ending as I would have been in the ditch. The more you drive these cars in the snow/ice I'm sure you will start to have a good idea of how they react to different situations. Also, just wondering if say the 50% 50% torque split was in play, is there any torque steer in front, as that may have been what I was feeling. Something that actually pulled my front tires out of those ruts as I tried to turn left rounding the corner. Just after I slightly lifted off the throttle, the fronts started to bite. I guess it could be torque steer f and some under steer from the LSD in the rear as well.
 

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Traction control can and will cut engine power when it senses slipping in one wheel. So turning it off to spin through some snow seems reasonable, you cannot, however, disable vdc or rollover control so the system is not completely off. VDC will use brakes to try and keep the vehicle pointed the direction you are intending it to go according to multiple sensors in the vehicle.

Are you using snow tires?
So, I have Nokian Hakkapeliitta R3 SUV studless tires and am using my B9 as a ski rig. This past week, I was traversing up hill in snowy dark conditions 27 degrees with a rutted road with ice in the ruts. Going around a curve the car started to pull off line. I slightly released the throttle just in time as there was not a guard rail, only a ditch on the outside of the curve. Slowly the steering and front tires started to grip and return to the direction my steering wheel intended. This is the first time I have experienced this torque steer effect. Then with less throttle, it released its push/pull and returned to the intended ruts. Maybe the rear end was locked up and this was merely an understeer event. Just scary with 5 vehicles behind me.
 

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If you are going through deep snow first thing to do is shut off the traction control. You need momentum to keep going, especially if you are going up a hill, and the traction control kills your power and thus your momentum as soon as you start to spin a tire. Any car can loose the track on a slick road, even a Subaru. AWD does not overcome physics. I bought mine just to drive up in the mountains on logging roads when it is too cold for my quads or SxS's. It has performed well but has it's limitations, I'm sure I put mine through more than a lot of the people who own one. I find the ground clearance to be it's biggest limitation. Is fine for almost anything you'll find on a paved road. I've found it works great until the chassis starts dragging the snow, once the snow gets as deep as the front license plate it is time to turn around :)


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This car with Torsen LSD in front and rear and a LSD for a torque split controller between the two makes for a complicated system. That's what I am talking about. Just seems that the rear was pushing me straight, while the front wheels were turned as in understeer. Then once I lifted off the throttle, the fronts regained traction and the car steered back from the edge of the road and ditch. So the center torque splitter changed the torque distribution when I lifted of the throttle and that allowed the fronts to regain traction. The other cars behind me did not seem to have this same experience, so I think each system has its pluses and minus's. The other idea I have is that I made a mistake not having these tires studded. With this car, I think studs would work very well. I just did not want to hear the noise of the studs, but if they really adds traction in the corners, well then next tire time it will be studs. So, you are thinking you need more under car clearance? That;s a F150 territory? My idea is stiffer sway bars f and r. Car seems to have too much learn. I saw a guy put WRX swaybars on his car, he said it improved the handling and exposed the lack to seat bolsters as he now slides around in his seat much more in corners.
 

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Maybe the cars behind you had no problem because they saw you slide and let off the gas :) Yes if I wanted to go into deeper snow I would need something with more ground clearance, like my F250, but that would just end up getting me somewhere I really shouldn't be, so I'm gonna stick with the Tribeca as my back up woods ride.
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I snowmobiled for over 20 years so have spent a ton of time driving in the snow. If I lived where it snowed in town I would run studs during the winter. There is nothing that gives traction on ice like studs, nothing.

Yes different drive ratio's don't help. I don't understand why they would want to have more power to the rear tires in slick conditions. Just look at all the mustangs and camero's in the ditch when it gets snowy. Rear wheel drive sucks for winter driving.
 

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89, when do you push the traction control button off. At a standstill or moving, and at what speed. If you push the button going down hill does it change the steering much if you are on icy roads, using the engine brake? I want to know about the torque splitter effects as much as possible. Subaru does not publish any how to use videos on the intent of their setup and how the electronics also affect the splitters activity. Does 50/50 split going down hill on ice help or hinder steering and braking? Which one and how do you correct if you start sliding? What happens if you are using manual mode with the button pushed down hill using engine braking as some actual brake as well. Will the front slide more with this setup than the 45/55 mode or are other nannies being used to control individual wheel lock using the brakes.
 

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Maybe the cars behind you had no problem because they saw you slide and let off the gas :) Yes if I wanted to go into deeper snow I would need something with more ground clearance, like my F250, but that would just end up getting me somewhere I really shouldn't be, so I'm gonna stick with the Tribeca as my back up woods ride. View attachment 2541 View attachment 2542 View attachment 2543 I snowmobiled for over 20 years so have spent a ton of time driving in the snow. If I lived where it snowed in town I would run studs during the winter. There is nothing that gives traction on ice like studs, nothing.

Yes different drive ratio's don't help. I don't understand why they would want to have more power to the rear tires in slick conditions. Just look at all the mustangs and camero's in the ditch when it gets snowy. Rear wheel drive sucks for winter driving.
The 45/55 split I think works most of the time, but the rear Torsen LSD does cause some understeer uphill in icing conditions. Then, I felt the fronts start to grab hold as the VTD went into the 50/50 mode. Seemed to take about 1 and 1/2 seconds to change from 45/55 to 50/50 through the planetary gear-type center differential and a electronically controlled hydraulic transfer clutch. If you pushed the button, will it change almost instantly or does it take time for the hydraulic ram on the splitter to react?

Attached is Media Information bulliten from Subaru

"The Variable Torque Distribution (VTD) version of Symmetrical All-Wheel Drive utilizes a planetary gear-type center differential and an electronically controlled hydraulic transfer clutch to control power distribution between the front and rear wheels. Under most conditions, VTD splits the power 45:55, with the rearward bias contributing to handling agility. The VTD system continually optimizes power distribution in response to driving conditions

Vehicle Dynamics Control (VDC) is a sophisticated stability system that actively controls the center differential’s power distribution as part of its function. VDC ensures optimal torque distribution to the appropriate wheels based on input from steering wheel angle, yaw and lateral g-force sensors. The VDC system also monitors input from the ABS brakes, adjusting individual wheel braking as needed, helping to maintain vehicle control under a variety of driving conditions. Integrated with VDC, the 4-wheel electronic traction control system (TCS) provides an extra layer of handling control without impeding VTD All-Wheel Drive operation."

Also, do I need to change the planetary gear-type center differential oil sometime. I'm thinking the Ford dealership changed the transmission fluid, but did not change the Torsen LSD's f or r fluids. They changed the brakes new tires and other stuff, but I recieved no records, nor will Subaru tell me what the women who drove the car for 108k did as far a maintance goes. Ford sales at Chuck Colvan Ford in McMinnville, Ore, said they had a stack of receipts but could not give them to me. They traded the Tribeca in for a new Ford 150.
 

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From the front LSD dip stick, the oil looks clear and fresh. So, the only question is the center differential oil. Overall, I am starting to enjoy driving the car in snow/ice up hill and down. Its just a little unnerving sometimes as the VTD and VDC systems do work together. I'm not sure I can feel the TCS system though. A couple of days ago, I was in the Crystal Mountain parking lot, that was frozen solid ice win just a little snow on top. You could see the ice clearly though especially when walking on it with ski boots and skis on your shoulder. Man as it slick. Waiting for the Ford 250 powered twin slay trailers that take skiers to the lodge, I witnessed a number of Dodge, Chev and Ford trucks spin there rear wheels, then had to shift into 4 wheel drive to get traction. They must driving with only the rear LSD ingaged to allow for better steering input, especially up hill. Our Symmetrical all wheel drive seems a better system. but more complicated. Just wonder about the Audi and BMW systems, how do they compare on ICY up hill roads with good snow/ice tires but not studs. I'm currently using Nokian Hakka R3 SUV stud less 255/55/18' on OEM wheels.
 

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The B9 has the same setup as the STI, two torsen mechanical LSD. These are not open differentials, so when you push the traction control button, the center diff changes from 45/55 torque split to 50/50 allowing the mechanical differentials to run all 4 wheels. The downside is steering is compromized causing understeer around uphill corners, as the back end will want to push straight ahead, while the fronts are trying to turn all at the same speed. So if you are going uphill on an icy road, with the button pushed, you will have understeer in a big way around corners, just push the button again to change it back to its normal 45/55 torque setting. Its great 50/50 in deep snow but not so much in rutted icy uphill roads. I leave the traction control on so the fronts can steer and the VDC actively controls the center diff power distribution and from steering wheel angle, yaw and lateral g force sensors. The 4 electronic wheel traction TCS traction control system adds another layer on top of the mechanical one.

Edmonds used car web site reports 2007 Tribeca Specs and features report LSD in middle and rear differentials.

Most info I have recieved showed the Tribeca having the same all wheel drive system as the STI including both front and rear LSDs. This is a copy from Google of an 2015 road and track summery of Subaru all wheel drive systems. The Tribeca is an advanced all wheel drive system for its day. Its got both mechanical all wheel drive and electronic all wheel drive. My problem with the system is its a little clumsy on a curvy icy road. This didn't seem to bother 5 other cars directly behind me. They may have had studs on their tires though.
Side-to-side?
That pretty much covers, at a glance, how modern Subaru's split torque from front to back, but what about the side-to-side or left-to-right torque split? On both the front and rear axle, you'll generally find a standard open-type differential, but performance models (such as the WRX and the Legacy-based 3.6R models) will often feature a limited-slip differential on the rear axle to help with rear-end grip when cornering.
The WRX STI also features a limited-slip differential on its front axle for maximum all-around grip, and the newest 2015 WRX and WRX STI also make use of a brake-based torque vectoring system that bias-brakes the inside wheel when cornering to improve power transfer to the outside of the turn and tighten the turning radius.

You can google Torsen LSD mechanical diff. There are numerous discussions on the topic vs clutch style LSD.



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@apex1, gotta say - you are high or something along those lines :D

1) about b9 having torsens in front and rear:
to be exact - 38335AA000 Genuine Subaru Converter Differential Assembly
do you really think that torsen differential will cost 250bucks new? :)))))

visco diffs cost at least 3x that - 27020AA050 - Viscous LSD. EXC.VDC - Genuine Subaru Part

and this is front:
Can you show me any part that is LSD-ish, not open differential vulgaris?

2) my guess - you mistake VTD/VDC with lsd differentials.

3) middle diff:
can you show me in this center diff diagram any LSD parts?

4) I don't see any STI-iness in Tribeca. and using edmunds.com or car and driver magazine as a source... how about excerpts from FSM or, at least, sales brochures, subaru technician booklets or something really technical?

5) about "torsen LSD" - I feel it as bad combination of terms. Personally, when I hear "LSD" I understand it as clutch/disc type (both wheels block at some speed differences, either wheel can be off the ground). when I hear "torsen" - well, it's "torque sensing" (mathematically - torsen can be formulated as multiplication, when one wheel is up in the air - result is zero). but, ok. I am sometimes unpleasent because of different points of view :D
 

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OK, I will search the literature again to find the exact Subaru sales aid that mentioned the mechanical differentials both front and rear. This is exactly how all 4 wheels spin when the magic button is pushed turning off the electronic aids. I have watch numerous videos of Tribeca's going up hills where other SUV's spin one wheel f and one wheel r. The car needs two mechanical LSD's to make all 4 wheels spin at the same time. The electronic nannies only use the brake to slow down the spinning one and hopefully start the opposite side to spin. But, when the Traction Control button is pushed that electronic brake system is off and the remaining 4x4 mechanical system is fully engaged.

This TCS Traction Control System is the same system employed by the Outback 3.0 R VDC Limited Wagon.

89Sandman can certainly give his impression as to the 4x4 capabilities and how that is possible only with the aid of LSD. Open differentials simply do not work as 4x4 unless the hubs have a locker.
 
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