[Northern_aqs]

Good afternoon, thank you for any advice you can offer.

The Car:
2000 OB Wagon Limited, 2.5/AT, 140k miles. Engine was out and rebuilt at a shop (not by me) approximately 15k ago. Transmission and front diff have sufficient oil shown on the dip stick. There is/was a persistent slow weep at the front passenger axle seal, so fluid was always monitored regularly.

My wife was driving the car when she heard a pop noise, now followed by loud persistent banging with vibration when the car rolls, persistent coasting or driving in gear or out. Banging is quite loud. I originally thought failed CV joint and took it to my mechanic (under its own gruesome sounding pwer) in the neighboudhood. On the hoist he says the CV joints are all fine that its an issue somewhere in the front diff. Driven with all wheels off the ground it has AWD for five seconds, then FWD only. No transmission codes.

Any experience with something similar; is a failed front diff the only and likely problem or are there other possibilities? (solenoids. etc?)

The mechanic is not particularly subaru fluent and I am not comfortable paying him to learn to be. I love the car but am looking to make an intelligent decision about fishing or cutting bait.

 

[subiesailor]

CV joint could be broken but appear fine from just looking at the boots externally. That would be the most obvious and has been found to be the cause of this type of thing.

Did this shop do the engine rebuild?

 

[cardoc]

When the car was up on the lift, did you hear any noise from the front differential?

Was there any noise from the main body or tail section?

Rear Diff noise?

Without seeing the car in person and hearing it, it would be hard to determine. What you describe is typical of a broken CV Axle. Are you sure the axle was not broken?

 

[Northern_aqs]

Thanks for the response. It was a different shop that did the rebuild, subaru specialists, engine rebuilders only.

The fact that when on the hoist in drive, it changes to fwd only after 5 seconds leads me to believe it isn't half-shaft or cv joint related. I will suggest that they plug in the fuse to disable the power distribution to the rear wheels to see if the noise persists.

 

[cardoc]

The car is FWD with AWD capability. Just because the rear are not spinning does not mean damage to the center differential. Especially is it was just idling in gear.

In the air or off the ground, speed the engine up in gear and see if the rear begin to spin. And listen for noise.

 

[Northern_aqs]

I wasn't present when they put the car on the lift, but will trust their opinion re-cv joint at this point. The banging appears to be mid-ship by the front differential, from their description.

 

[cardoc]

Get another opinion. Damage to the front diff is sparse. Axle breaking, lots.

 

[subiesailor]

Always confirm the cheap common things are not the cause first! Any shop angling to make money will sell you on the most costly possible option "Hey buddy you need a new transmission" They charge you for it then fix the broken axle and give the car back to you. See where thats headed? I do

 

[Northern_aqs]

The sound is identical to the one in the top video in the link below:

http://www.subaruoutback.org/forums/66-problems-maintenance/47572-loud-popping-banging-noise.html

Too bad there was no resolution posted.

 

[subiesailor]

Sounds exactly like a busted CV joint. Not uncommon to any vehicle that uses them. Though seems to be an easy money maker to charge big money for a simple fix.

 

[cardoc]

Check the rear drive shaft carrier bearing and u-joints.

 

[Northern_aqs]

I normally do all the work on my car when time and equipment allows, I outsourced this because I'm swamped at work. I'm going to have to make time to look at this myself though.

Front cv's/half shafts: my experience has been that the sounds/grinding changes with turning direction: no change with this situation. If the joint is broken sufficient to make a banging noise, I expect to be able to move/distort the joint manually from underneath.

Rear cv's/half-shafts: sound won't vary with turning under all circumstances, but I should be able to manually distort from underneath if they've failed.

If my understanding of the 4eat is correct, if I insert the fwd fuse, the solenoid to lock up the front diff/deliver power to the rear won't function; rear drive shaft will free wheel with the wheels on the ground, however on a lift the driveshaft shouldn't turn, am I correct? With the engine off, trans in neutral, I should be able to manually rotate the rear wheels to listen for rear diff sounds, right?

 

[cardoc]

I normally do all the work on my car when time and equipment allows, I outsourced this because I'm swamped at work. I'm going to have to make time to look at this myself though.

Front cv's/half shafts: my experience has been that the sounds/grinding changes with turning direction: no change with this situation. If the joint is broken sufficient to make a banging noise, I expect to be able to move/distort the joint manually from underneath.

A break in the joint does not necessarily mean total separation. It could be a knuckle chipped and the ball is catching on the chipped portion. A total break in a front axle would not allow movement of the car until the MPC engages the rear wheels. And when the car does move, it is really slow because the transmission and engine will be turning at a high rate of speed while the rear is only receiving a low ratio.

Rear cv's/half-shafts: sound won't vary with turning under all circumstances, but I should be able to manually distort from underneath if they've failed.

If my understanding of the 4eat is correct, if I insert the fwd fuse, the solenoid to lock up the front diff/deliver power to the rear won't function; rear drive shaft will free wheel with the wheels on the ground, however on a lift the driveshaft shouldn't turn, am I correct? With the engine off, trans in neutral, I should be able to manually rotate the rear wheels to listen for rear diff sounds, right?

Yes, fuse equates to FWD only. The rear shaft will spin independent of the transmission in park or neutral. It will not spin with the wheels on the ground since it is connected to the differential assembly unless there is a break in the rear differential.

If the car is on a lift, the rear wheels may turn due to static friction of the clutches. If you want to test the rear shaft for free spin, raise the car, set the park brake, with the fuse installed run it in gear. You will only have the resistance created by transfer of torque to the front wheels since the rear should not turn. If there is an excess of resistance with the brake on, that would indicate a problem with the center diff.

Yes/maybe/no on hearing a problem with the rear differential. We went through this with a forum member's XT. A lot of this doesn't make since, this is not possible and not supposed to be happening. No noise from the rear diff, the wheels would spin with the front in the air, but only FWD on a car with a VTD center diff meaning it is predominately RWD, when the car is on the ground. Ended up being a break in the rear diff or the axle stub. I don't remember which.

 

[Boxxerace]

I've not extrapolated a large amount of symptoms in this thread, but there's always a chance you have run into the same issue I have:

Here's one of the threads pertaining to the source of my problems: http://www.subaruoutback.org/forums...ont-go-back-spring-retainer-style-joints.html

This is in an 04, but the rear ends are basically the same from the late 90's to today. All Hitachi R160's.

Good luck on figuring this out - and do listen to Cardoc, he's more experienced than the average bear.

 

[wilsonhp]

Is it possible that the bolt holding the harmonic balancer on the shaft broke, and the key is banging back and forth in the keyway, wallowing it out?

Sounds like what happened to my wife's Impreza. She said it sounded like a helicopter while it was running.....

 

[Northern_aqs]

I'm just in the process of having the car towed home from the shop so I can take a look before making any deciso

 

[Northern_aqs]

-sorry, bad typing on an iPhone.

-before I make any decisions. The engine runs and idles smooth as ever, but I'll check for end-play in the balancer. I assume its not hidden under the timing belt covers and should be easy (ish) to check the run-out. When I drove it last, it felt like it was rolling on one square tire, it points to driveline, but everything is worth checking out.

I called around for prices for a front diff if that's what comes to bear. A shop recommended by my engine builder can supply and install a used take out with 60,000 miles (100,00km) in Toronto (local to me) for $1600, does this sound reasonable for a 6 month warrantied item?

Thanks to all for their assistance, Subaru owners are a model for all gear heads.

 

[CNY_Dave]

Having a shop swap the trans for a used one would probably be $1200 at the low end.

If you get a transmission make sure it's not from a 2004...

 

[cardoc]

-sorry, bad typing on an iPhone.

I ate t whe tht hpns