1999 Legacy Outback Gear Backlash Noise

[Kingkoopa]

I am having some gear backlash noise in my '99 Legacy Outback transmission. I don't think it's excessive, but the only comparison I have is to my '94 Legacy L. Both are 5-speed manuals. The '99 has about 200k miles, the '94 has about 300k miles.

 

I hear the same backlash noise in my '94, but it doesn't sound as loud, but that may just be because the car as a whole is much louder than the '99 and is making comparison hard.

 

I'm pretty sure the backlash noise is coming from the front diff because I can hear the backlash while slowing down with the car in neutral and the clutch engaged. So, I still hear the noise with all gears in the transmission spinning at a constant rate. The noise decreases in pitch as I slow down and stop. I can hear it while slowing down in neutral, but it is definitely louder when the car is in gear and I'm slowing down using engine braking. 

 

So to the question. Is a noticeable amount of backlash noise normal for these transmissions or should I have something to worry about. Or at least normal for transmissions with this many miles. I've checked the transmission fluid and it's level is perfect and as far as I know, the front differential shares it's oil with the transmission. Please correct me if I'm wrong. 

 

Let me clarify that I have absolutely no noise when the gears are in forward motion. The transmission is very quiet while accelerating and on the highway in every gear. 

 

Thanks for any insight. 

[Kingkoopa]

Shameless self bump.

[ccrinc]

Gears in reverse always make more noise than in forward.  Only you can judge if it's exceptionally noisy for your car. 

While the level may be good, when is the last time you changed the fluid? It needs to be done about every 12-15,000 miles.

 

These are both high mileage units, so a fluid change may be just what the dr. ordered.

[Fairtax4me]

What do you mean by backlash noise? Is it a chatter? Whirr? Groan or grumble? High pitch, low pitch, changing pitch? Does it change based on engine speed or wheel speed?

[darnold]

What do you mean by backlash noise? Is it a chatter? Whirr? Groan or grumble? High pitch, low pitch, changing pitch? Does it change based on engine speed or wheel speed?

I have an 05 Legacy that sounds like the same thing.  I would call it a grumble.  Changes based on wheel speed.  Same sound with engine at idle.  No vibration from shift lever.  Definitely sounds like it's coming from the front.  Disappears below 20 km/hr.

 

Does the transmission and front diff share the oil?  I've found oil dripping from a hard line on the left side near the front cv.  Is there a transmission cooler and could I be losing oil?  I got under and tried to see how to check the oil but couldn't see an obvious level plug. There is never a drip stain under the car.  I got under after driving and didn't feel anything that seemed hot to the touch.

 

I would like to figure this out before something bad happens....Any advice would be welcome and appreciated.

 

I did see the post about changing the oil and I will do this as soon as I can figure out the drain and fill plugs.

[Fairtax4me]

Darnold yours is probably a wheel bearing.

 

Is it auto or manual? The autos do have a cooler built into the radiator. The steel lines can rust and leak. Also the rubber hoses can deteriorate and leak at the ends.

[darnold]

Thanks Fairtax.  That seems reasonable to me.  It is a manual transmission and I had a look last night after I posted and finally found the transmission dipstick.  It is full and clean. How complicated is it to replace wheel bearings?  I am quite well equipped in my shop at work.  Does the wheel hub have to come right off the cv axle? I guess the question I'm asking is can I screw up the alignment while I'm doing this and how do I avoid it.

[idosubaru]

Original poster - how do you know it's backlash and not a failing bearing in the front diff? Folks have seen bearing failures in the front diff.

Auto's don't share trans and front diff fluid.

Manuals do.

 

Front diff noises usually get worse over about 1,000 - 10,000 miles.  I would consider yourself very lucky if it actually lasted.  You should know soon enough, it's going to get louder or it's not.

 

retaining alignment:

 

mark the bottom strut mount bolt head orientation to strut bracket - and reinstall to the same location - to retain alignment.

 

if tie rod gets disconnected - draw a line across the outer tie rod, lock nut, and onto the inner tie rod. then count number of turns removing.  (i just did one today and it was 16.5 rotations to remove the tie rod).  reinstall those number of turns and line up your marks you made.

 

05+ wheel bearings are easy - they're bolt on, no press or anything needed.  Super cake.  I'd get Subaru units.  Aftermarkets sometimes cause ABS issues because the tone ring is integrated with the wheel bearing assembly on 05+ models. Afermarket bearings/tone rings freaks out the ABS sometimes.

 

You can readily google common/routine jobs like this and even download the Subaru Factory Service Manual for free online.

[darnold]

Changed my front left wheel bearing this morning.  Didn't cure the noise.  While I had it up though, I turned the shaft by hand and sounds like the left bearing on the front diff is making noise.  Can these be changed without pulling the diff?  Right side sounds fine.

 

Thanks

Edited May 8, 2015 by darnold