Speed dependent Clicking

[greenleg88]

2000 Impreza outback sport - Manual Transmission 209k miles

 

Hello all -

It has been a while since I have been on here, but I know this message board is full of knowledge, and I'm having some trouble diagnosing a speed dependent clicking noise in the drive train somewhere.

 

The clicking started before my last major project, in which i replaced:

- All 4 Struts

- Steering Rack

- Both Tie rod ends

- Rebuilt power steering pump

- Both Front Axles

- Both lower control arm ball joints

- 4 New Tires

- Transmission fluid (prior to this project, but still recently)

 

Many may immediately jump to CV joint, but noticed the wear from the old damaged ones, and that is no longer noticable with the new axles, so i have ruled those out. The noise is speed dependent, i can feel the clicking in the shift knob, and when the clutch pedal is partially depressed, the noise is significantly louder.it is a relatively fast click - i think it is similar to the sound made when two wheels are off the ground, and you rotate the wheel one direction, and you hear the clicking from the differential. Seems to be speed dependent only and can be heard in any gear.

 

 

My thoughts are:

- Clutch - would a broken finger from the pressure plate cause such a clicking?

- Differential

- Transmission

 

 

 

any help would be greatly appreciated. I do need to drive the car across the country in less than 5 days.

[greenleg88]

i have had mismatched tires on the car, for a while, and based on my research, am quite confident it is an issue with the center differential. can anyone confirm this? and perhaps comment on how long these can be driven on like this before a catastrophic failure. i have driven less than 100 miles since hearing the noise.

 

although...i am not experiencing torque bind (yet?) and perhaps i will eventually i imagine...? i was reading this thread - http://www.subaruforester.org/vbulletin/f89/center-diffs-how-replace-them-46979/

Edited June 12, 2014 by greenleg88

[1 Lucky Texan]

binding in the MTs is usually reported as worse when the tranny is hot.

 

You might consider checking the u-joints

 

maybe I missed it but, do you heear the same sound at the same rate if you coast in neutral at idle? that is 'speed dependent' meaning speed of the CAR?

[greenleg88]

speed dependent was supposed to mean speed of the driveline. BUT

coasting in neutral at idle, the sound is very very quiet, but i if i can hear it, it would be at the same rate i believe.

coasting in gear, off load, the noise is quite noticeable when the radio and blower fan is off.

on load, the noise is there, but tough to pick out over the engine of course.

 

a partially engaged clutch, while shifting gears makes it a very loud noise.

 

[1 Lucky Texan]

seems a little like transmission shaft bearing

 

I wonder if the transmission's magnet on the drain plug would show excessive metal sludge?

 

If you could record the sound, others here might be able to diagnose it. I wouldn't, but there are some very experienced guys here.

[Fairtax4me]

The early phase 2 transmissions had some problems with the center differential and transfer gears.

Pull the tailhousing off and I bet you find a chewed up snap ring and a tooth missing or chipped on one of the transfer gears.

Usually does NOT affect the rest of the trans. Pop a new center diff and transfer gear set in there and you should be good to go.

[greenleg88]

I will work on getting an audio clip up.  

 

thanks for the replies

the tranny fluid was changed within the last 5000 miles, and there was certainly a bit of metal on the magnet (picture soon) 

 

 

if that is the case, with the center differential and transfer gear, how long have people been driving on them before immediate attention was necessary? i am not too familiar with the parts of this transmission and have been trying to look at different diagrams to get a better understanding. what type of damage occurs when the center differential completely fails and what is the worst case? 

[1 Lucky Texan]

you might find a compatible used tranny at a decent price - maybe with 1/3 the mileage of yours.

[Fairtax4me]

Generally you don't get to drive on it for too long when it starts making noise.

The snap ring that holds the center diff carrier together pops out or part of it pops out and gets jammed up in the transfer gears.

When the transfer gears shred they put a bunch of metal chunks everywhere, but the big stuff doesn't really make it into the main part of the trans. But it will get into the center diff, transfer and tailshaft bearings and cause damage to those. Eventually they will shred and the tailshaft will start wobbling around like an out of balance wheel. Then the tailshaft housing explodes from the momentum of the rear driveshaft flopping around.

 

With the snap ring gone the center diff housing can pop apart. Then the center diff will chew itself up. Then you go nowhere.

 

Either way, it spells bad.

[greenleg88]

Generally you don't get to drive on it for too long when it starts making noise.

The snap ring that holds the center diff carrier together pops out or part of it pops out and gets jammed up in the transfer gears.

When the transfer gears shred they put a bunch of metal chunks everywhere, but the big stuff doesn't really make it into the main part of the trans. But it will get into the center diff, transfer and tailshaft bearings and cause damage to those. Eventually they will shred and the tailshaft will start wobbling around like an out of balance wheel. Then the tailshaft housing explodes from the momentum of the rear driveshaft flopping around.

 

With the snap ring gone the center diff housing can pop apart. Then the center diff will chew itself up. Then you go nowhere.

 

Either way, it spells bad.

hmm. well that was informative..  i just got 4 brand new tires mounted and balanced on the car, and there is definitely a shake at about 60 miles an hour. i am thinking about bringing the wheels to get balanced again, as i dont recall this shake being there before the tires were changed (but the noise was still present)...  

 

any other thoughts or ideas to make this a definitive diagnosis and not something such as throw out bearing which was mentioned (because of the elevated noise while clutching).speaking of which, what do bad throwout bearings sound like...? potentially similar kind of rolling/humming/tick?

 

 

These are the two gears you suggest replacing? plus the center diff which slides onto that splined shaft..

http://img530.imageshack.us/img530/5863/trannydiff017kg3.jpg

 

i saw you made a few posts about someone else working on a similar project.  any thoughts on where to sources the parts [people seem to be getting lucky and finding parts for <$300, but the center diff alone seems to be about 500], and estimated time to complete the job [seems like 3 hours... assuming no broken bolts]?  (potentially with access to a lift)

Edited June 13, 2014 by greenleg88

[Fairtax4me]

A bad TOB will make noise based on engine speed. Either a grumbly whine or a rattle sound. TOB will make noise with the car sitting still.

 

Center diff and transfer gears will only make noise when the car is moving.

Engaging/disengaging the clutch while moving changes how much load is applied to the coast and drive faces of the gears.

 

When coasting in neutral there is little or no load since there is no power input from the engine. The gears will be lightly riding on the coast face.

 

When changing gear, there will initially be deceleration load on the coast face of the gears, which then changes to load on the drive face of the gear as you roll into the throttle.

 

The load will also shift from coast face to drive face with light changes in throttle while driving as you cruise.

 

There is also thrust loading of the bearings taking place due to the helical cut of the transfer gears. Thrust loading causes the gear to try to push fore/aft as the load on the transfer gears changes. If one of the bearings is making the noise it can change depending on the thrust load being applied to it.

[1 Lucky Texan]

209K miles trans guys - can it be repaired? of course.

 

I would just shop for a replacement used trans., Inspect fork, flywheel, clutch, change TOB w'ever when you install the new trans, fresh non-synth GL-5, drive for another 100-200K miles.

 

done and done

[greenleg88]

So i suppose the plan is to replace the transmission as soon as possible... which wont be possible for at least a few more weeks.

 

The clicking has developed into a significantly more noticeable whine sometime in the last 80 miles or so. In my past experiences, it does sound more like a brinelled bearing than a gear missing teeth.

 

 

Perhaps someone could take a listen and make some comments?  Im hoping can still squeeze out another 1500 miles out of this very sad transmission as I am in the middle of the country in Kansas at the moment.