Welcome me to the 'noisy front diff' club - Page 2 - Subaru Outback

cardoc · 01-10-2013, 01:25 PM

Dave, that sounds bad. Hard to tell exactly, but seems like bearings or loose pinions.

H-D · 01-10-2013, 04:19 PM

The shiny portion of the debris reminds me of British motorcycle gear boxes I have failed. I wrote those off to poor under-surface gear hardness. With the ability of these cars to handle slippery conditions; could transitions between spinning & high traction be exceeding the robustness of the differential pinions? Have a '57 Chevy that wheel-hopped & broke these gears until heavier rear spring main leaves stopped the wheel-hop. I've considered all pinions with a prejudiced eye ever since.

CNY_Dave · 01-10-2013, 05:11 PM

The lucas didn't change the noise, and it hasn't gotten worse... yet...

I've been careful to not spin the tires when transitioning from low traction areas to high traction areas. I did in a worn '92 ranger drive shaft that way once...

Noise started over the summer.

CNY_Dave · 01-19-2013, 05:33 PM

Noise with rear wheels on the ground and not moving:

Bad front pinion - YouTube

I think this is definitive, front pinion bearing.

I also confirmed even in 1, there is NO drive to the rear wheels until you step on the gas (whern I had all 4 off the ground, heh)

cardoc · 01-19-2013, 06:21 PM

Quote:

Originally Posted by CNY_Dave

Noise with rear wheels on the ground and not moving:

Bad front pinion - YouTube

I think this is definitive, front pinion bearing.

I also confirmed even in 1, there is NO drive to the rear wheels until you step on the gas (whern I had all 4 off the ground, heh)

That's because your LL Bean uses the MPC and is predominately FWD.

CNY_Dave · 01-19-2013, 06:47 PM

Yeah, 90% FWD until something slips, but 1, 2, and R make it much more evenly split as soon as slippage occurs.

There was controversy, though, about when you put it in 1, 2 or R if it was 'locked' into 50/50 (MPT as engaged as it ever gets, anyway) or if slippage had to be detected first.

Even so, it was much quicker to drive the rears in 1 than in D, so 1 is certainly better for grip than D.

plain OM · 01-19-2013, 07:00 PM

We covered this in quite some detail in the FreeSSM thread. Lots of data on where the AWD control duty cycle signal is under different conditions.

The control responds not only to slip, but to risk of slip represented by throttle position, engine torque, wheel speed, gear etc. You don't need any wheel slip to see the control go from the base level of around 30% duty cycle (which in itself is significant) way up to 90% or more based only on throttle position. That's what distinguishes the Subaru full-time AWD from other makes that are in fact FWD until slip is detected and then they go switch to AWD (it's either on or off, without anything in between as with the Subaru.)

In 1st gear, the rate at which the duty cycle responds to factors other than actual wheel speed differences (aka slip) is faster than in the higher gears, but that corresponds to the fact that torque to the wheels in the higher gears isn't as great as in the lower gears, so the risk of breaking traction in the lower gears is higher.

It's a fascinating and very responsive system when it's working.

CNY_Dave · 01-21-2013, 12:47 PM

Trans is in the hatch, $860, 96k on it, out of a 2004 LL bean.

Came with the converter and I asked them to leave the mounts on.

CNY_Dave · 01-25-2013, 11:11 AM

On the way home last night I thought I may have smelled gear lube.

Pulled the car in the garage last night, am starting the trans swap.

There's oil under the car.

I'm goin' in.

CNY_Dave · 01-25-2013, 11:22 AM

Yah, it's front diff gear lube.

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01-10-2013, 01:25 PM	#11 (permalink)
cardoc Registered User Join Date: Aug 2012 Location: Austin Car: 2001 VDC, 2000 Outback 5MT (on the cheap) Posts: 3,010 Feedback Score: 0 reviews	Dave, that sounds bad. Hard to tell exactly, but seems like bearings or loose pinions.

01-10-2013, 04:19 PM	#12 (permalink)
H-D Registered User Join Date: Apr 2011 Location: NW TN Car: '99 Outback 2.5 GT auto & '97 LegOB w/ grossly insulted 2.5 Posts: 138 Feedback Score: 0 reviews	The shiny portion of the debris reminds me of British motorcycle gear boxes I have failed. I wrote those off to poor under-surface gear hardness. With the ability of these cars to handle slippery conditions; could transitions between spinning & high traction be exceeding the robustness of the differential pinions? Have a '57 Chevy that wheel-hopped & broke these gears until heavier rear spring main leaves stopped the wheel-hop. I've considered all pinions with a prejudiced eye ever since.

01-10-2013, 05:11 PM	#13 (permalink)
CNY_Dave Registered User Join Date: Nov 2007 Location: central NY USA Car: 2003 LLBean H6 Outback Posts: 3,354 Feedback Score: 0 reviews	The lucas didn't change the noise, and it hasn't gotten worse... yet... I've been careful to not spin the tires when transitioning from low traction areas to high traction areas. I did in a worn '92 ranger drive shaft that way once... Noise started over the summer.

01-19-2013, 06:47 PM	#16 (permalink)
CNY_Dave Registered User Join Date: Nov 2007 Location: central NY USA Car: 2003 LLBean H6 Outback Posts: 3,354 Feedback Score: 0 reviews	Yeah, 90% FWD until something slips, but 1, 2, and R make it much more evenly split as soon as slippage occurs. There was controversy, though, about when you put it in 1, 2 or R if it was 'locked' into 50/50 (MPT as engaged as it ever gets, anyway) or if slippage had to be detected first. Even so, it was much quicker to drive the rears in 1 than in D, so 1 is certainly better for grip than D.

01-19-2013, 07:00 PM	#17 (permalink)
plain OM Registered User Join Date: Jun 2006 Location: Nepean ON Canada Car: 07 OBW 2.5i Touring (SE) D-4AT Posts: 6,905 Feedback Score: 2 reviews	We covered this in quite some detail in the FreeSSM thread. Lots of data on where the AWD control duty cycle signal is under different conditions. The control responds not only to slip, but to risk of slip represented by throttle position, engine torque, wheel speed, gear etc. You don't need any wheel slip to see the control go from the base level of around 30% duty cycle (which in itself is significant) way up to 90% or more based only on throttle position. That's what distinguishes the Subaru full-time AWD from other makes that are in fact FWD until slip is detected and then they go switch to AWD (it's either on or off, without anything in between as with the Subaru.) In 1st gear, the rate at which the duty cycle responds to factors other than actual wheel speed differences (aka slip) is faster than in the higher gears, but that corresponds to the fact that torque to the wheels in the higher gears isn't as great as in the lower gears, so the risk of breaking traction in the lower gears is higher. It's a fascinating and very responsive system when it's working.

01-21-2013, 12:47 PM	#18 (permalink)
CNY_Dave Registered User Join Date: Nov 2007 Location: central NY USA Car: 2003 LLBean H6 Outback Posts: 3,354 Feedback Score: 0 reviews	Trans is in the hatch, $860, 96k on it, out of a 2004 LL bean. Came with the converter and I asked them to leave the mounts on.

01-25-2013, 11:11 AM	#19 (permalink)
CNY_Dave Registered User Join Date: Nov 2007 Location: central NY USA Car: 2003 LLBean H6 Outback Posts: 3,354 Feedback Score: 0 reviews	On the way home last night I thought I may have smelled gear lube. Pulled the car in the garage last night, am starting the trans swap. There's oil under the car. I'm goin' in.

01-25-2013, 11:22 AM	#20 (permalink)
CNY_Dave Registered User Join Date: Nov 2007 Location: central NY USA Car: 2003 LLBean H6 Outback Posts: 3,354 Feedback Score: 0 reviews	Yah, it's front diff gear lube.

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