Powertrain issue I ran into last week

[Sumbex]

Last week, I was driving down a major highway, there was construction, and I hit a bump coming onto a bridge, and pop.. the right front axle assembly went. I pulled off the side of the highway... and the car wouldn't move at all.. the highway I was on has about a pick up truck width of shoulder. After stopping, I tried to pull the car off a little further and wouldn't move an inch. Which after being towed, made me wonder how the powertrain system on a 05 4AT legacy actually works? Wouldn't there still be power going to the front left axle and rear wheels? Atleast enough to pull it off the side of the road? Can any one please explain?

[GEE-OTTO]

Pretty sure the 4EAT Legacy 2.5i is basically a FWD car the power split is 90/10 or close, but it should have at least moved the car enough to get off the road.

[Sumbex]

Yeah, I would of thought even 5-10%(6-13HP) horsepower to rear would be enough to pull it further off the road, considering the area I was stopped on was downsloped/flat.

 

In the winter I ran into an issue where if the wheels slipped on snow the sports light would flash on, never got it to a dealer with it on though.(live about 45 minutes away) I wonder if maybe the speed sensors are malfunctioning

[GEE-OTTO]

In the winter that is common if you find yourself spinning if one tire rotates too many times more than the others you will get that light. I have a 08 2.5i 5MT this past winter i got in some deep snow started spinning the right front caught grip the other didnt and sure enough the lights flashed.

 

When i got out of the snow i reversed a bit the started forward lights went away

[RabidWombat]

When people say 90/10 split is really more of an approximation than reality. The viscous coupling is essentially disconnected, but since its not a true mechanical linkage, there's still some power transfer.

 

The powertrain is 90/10 default split with open front/rear differentials. To manage left/right power delivery the traction control system can apply the brakes to transfer torque to the other wheel.

 

In your case, the brake technique wouldn't work since the axle is disconnected. Due to the open differential, you will generate zero torque on the front wheels. The problem is that the sensors will see the front wheels as NOT MOVING rather than slipping. According to the computer, you have PERFECT traction in front. No matter how much power you transfer, you get ZERO slip. In those conditions, there's no reason to shift power to the rear wheels.

[GEE-OTTO]

Yup exactly what Wombat said

[naimouasta]

i thought i read somewhere that the 4eat/5eat and the sti 6spd are the only ones that can pull itself if an axle was removed. maybe it was talking about the driveshaft?!?

[FLlegacy]

That claim is made on nasioc by a few members, it was generally the older models of the sti, and all 4eat models, probably the 5eat is included.

 

The reasoning is that the 4eat is always transferring some amount of power to the rear so it will move the car using either front or rear wheel drive. I don't know if this is true just restating what I read. You can google it and see for yourself, it quickly turned into a battle of the AWD systems...

 

edit just noticed he is driving a 2.5i wich doesnt have vdc. The car should have moved even a little.