40 replies to this topic

[1 Lucky Texan]

Ever drained the gear oil out of a manual trans with a bad main shaft bearing? It comes out greyish black and full of silver swirls. It's not aluminum, the particles are so numerous not all of them get attracted to the magnet. Most of them end up settled in the bottom of the case like metal sludge. Magnets are useful, but the magnetic field only reaches so far, they can't pick out everything.

just seems to me, the magnet would be more loaded than he reported.

sweeping a magnet through some of the fluid should tell him if it's steel.

[the_bard]

...It comes out greyish black and full of silver swirls.

Yep, that's the color of the fluid.

wheel bearings

I initially thought the same, since the sound seemed to be coming from a distinct corner. The whole "sound moving around the car, swapping corners" bit threw me off, though. I've also taken it down a straight road without traffic, swerving back and forth across the lane, trying to load up the wheels. It didn't change any behavior in the noise. Regular turns didn't change it, either.

sweeping a magnet

I'll do that when I get home tonight, with a good strong magnet (from a hard drive).

[GeneralDisorder]

It's probably the transfer case/center diff support bearings. You can pull the transfer case and repair it as needed with the transmission in the car. The front VC/diff support bearing is a common failure item - so much so that it's stocked by most dealers.

Rear diff failure is exceptionally unlikely.

GD

Edited by GeneralDisorder, 30 November 2012 - 01:01 PM.

[the_bard]

I assume the failure of the transfer case support bearings has the same symptoms as a failed rear diff's pinon/ring gears? If so, I might want to buy or rig up one of those Chassis Ears (my wife has a spare stethoscope laying around I can butcher, I think... rig up a microphone and a way to secure the cable...) and have a listen to the transfer case versus the rear diff.

[88wacaroo]

I assume the failure of the transfer case support bearings has the same symptoms as a failed rear diff's pinon/ring gears? If so, I might want to buy or rig up one of those Chassis Ears (my wife has a spare stethoscope laying around I can butcher, I think... rig up a microphone and a way to secure the cable...) and have a listen to the transfer case versus the rear diff.

Well, can try to make this easier..you can loosen up the console and the shift boot and put your stetho thru the floor and have your wife drive and you listen...be careful you don"t blow the ears out;) I have a stetho I use and if it"s aloud noise WOW!! AC/DC at full throttle:eek:!! Good luck...

[Fairtax4me]

If you can find a way to attach the stethoscope to the diff housing you could run a long length of tube up into the car and just put it up to your ear.

[the_bard]

I sucked up my pride and dropped it off at the neighborhood shop this morning. They said they'd throw it up on the lift and give a listen; as long as they could diagnose it on the lift quickly, they'd give me a free diagnostic. They gave me a decent deal on pulling my right rear wheel and solving the slow leak (just a dirty bead; they cleaned it up and remounted it for $25).

They state the noise is coming directly from the transmission, not the transfer case or the rear diff. Their bet is the "main" input shaft bearing (front or rear, I don't know... I'll ask for clarification when I pick it up tomorrow; I'm not sure they'll be able to differentiate between the two simply by listening). Seems the 5MT has a bad rep for this, looking over the forums.

I can say that there's always been light noises from the transmission centered around what I expected was the throw out bearing (see http://www.ultimates...ad.php?t=131656 and http://forums.nasioc...d.php?t=2330624 ). I just never got around to address it, and those noises never got worse. Well, until a new noise showed up .

So now I'm thinking about pulling the transmission and following the guide here: http://www.ultimates...ad.php?t=90182 to take a look at that input shaft and its bearings. I get the impression that if the garage is correct that the bearings are bad, and the shaft itself isn't worn badly as a result, I can have a shop press new bearings on fairly economically.

If the shaft is worn, I ought to be looking for another transmission. If I totally botch the job splitting the transmission and looking at its guts, then I can chalk it up to a learning experience and replace it.

On the bright side, I expected transmission issues when I bought the Baja. The price was good enough that I could factor in another transmission and still come out cheaper than a comparative Baja in the Northeast. I'd rather not spend the money if I didn't have to (we're saving up for a downpayment on a house purchase), but if I gotta do it, I won't cry.

Update: My sister offered up her garage, a three hour trip away. It'll be better than trying to do it in mine (asphalt floor, not a level spot in the place). It'll just have to hold together for the drive. There's a local Pick A Part (U Pull It) yard there, too, offering up transmissions for $125. I'm thinking it might be worth it to pull one just to have it handy and have more options than simply replacing the bearings on my existing transmission.

Edited by the_bard, 03 December 2012 - 11:04 PM.
Update

[Fairtax4me]

If the input shaft double roller bearing is bad there are a few key indicators one of which I stated earlier. The gear oil on the dipstick will appear grey if wiped on a white napkin or cloth. There will be large amounts of grey glitter in the oil when drained, probably not as much as your differential, but it will be grey.
This bearing is spinning whenever the clutch is engaged, so if sitting still wih the engine idling you should be able to hear noise from the transmission. Depressing the clutch pedal will cause the noise to go away completely, and it will return when the pedal is released. Noise will coinside directly wih engine speed, will not be road speed dependent, and does not typically change pitch with throttle.
Mainshaft bearing failure typically does not happen until 150-175k miles. If fluid was severely neglected it could be sooner but at only 60k, mainshaft bearing failure seems a bit unlikely.
I've dealt with several bad main shaft bearings in various stages of failure. None have ever sounded like that.

Rear diff failure seems unlikely too, but we know the oil that came out of there was practically sludge.

Check transmission fluid condition and check for noise with clutch position before condemning the trans. Still sounds more like rear diff to me. Transfer shaft/center diff support bearing possible, but trans fluid condition will tell more.

[the_bard]

When we finally buy a house, I'm going to talk the wife into letting me spend a few grand on a proper lift. I'd feel more confident going into this if I could easily access the drivetrain without crawling around underneath it on the "not so level" asphalt floor of my garage.

There has been some noise from the transmission with the clutch engaged (pedal not pressed) in first and second gears, but it's been a distinctive gravel sound, much like that of loose heat shielding. I've been keeping an ear on that; the sound itself hasn't gotten worse, and it's nowhere near a whine. It disappears after third gear, or I can't hear it over the road/engine noise.

I wouldn't say that the fluid that came out of the rear diff was sludge; the viscosity wasn't thick. It flowed fine; the color and the "sparklies" were off, though.

I expected on changing the transmission fluid over this weekend, before I sent it off to the garage. That T-70 plug on the transmission stymied me, though. I'll pick one up later this week; the local Advance Auto Parts store carries them, so I luck out a bit. Got the gear oil and a nice new clean drain pan waiting.

Once I've got the fluid out, I'll take a few pics and post 'em here: the fluid itself; the drain plug (before wiping it down).

[forester2002s]

Trans. and diff oils:

In my experience when draining gear oils, a small amount of grey-fluff on the magnetic-plug is normal. And the drained oil might be slightly opaque, a hint of grey in an otherwise clear oil. And a few tiny metallic chips are to be expected. This is just normal wear on the gear surfaces. This never seems to go away, even on a high mileage vehicle.

On the other had, a lot of grey-fluff, and really dirty oil is bad news. And large metallic chips (especially in the transmission) are a sign of hard service.

My point is not to expect the drained oil to be in pristine condition.

[the_bard]

Oil change is done. Photos are up on Picasa: https://picasaweb.go...feat=directlink

There was sludge on the plug, with metal mixed in. Nothing huge, but I could pick out the pattern of the magnetic field.


If I had to guess, the sludge on the plug was less than a 1/4 of a teaspoon:


The oil was nasty, though; not the color I wanted to see:


Changing the oil did nothing to alter the symptoms. I wasn't expecting it, but it'd be nice to have been pleasantly surprised.

[Fairtax4me]

:/
Well now. That is awfully sludgy looking. The sound of stuff on the drain magnet is not out of the ordinary, but the fluid condition is another story.
I think we have a winner on the water contamination theory. Some kind of contamination of the fluid is the only way I can explain that much wear in both the trans and differential with such low miles. Besides the lack of chunks that fluid looks just as bad as the stuff I drained out of the trans in the 95 I bought last year. 225k miles and the mainshaft bearing had completely failed.
I assume you still have all 5 gears so you have some time yet. Eventually it will start popping out of 4th and/or 5th gear. Assuming the mainshaft bearing I the problem.
Still possible the transfer shaft bearings are damaged, actually I would bet most of the bearings are worn excessively or damaged in some way. Time for a tear down for inspection. I'm interested to see what kind of shape the internals of that trans and diff are in.

[the_bard]

Yep, still got all five gears. I'm kicking myself for breaking one of my cardinal rules (Always change all the fluid when you buy a new car); I let the "low mileage and only a few thousand to the scheduled maintenance anyway" convince me to just check the fluid levels and call it that. On the other hand, the damage may have already been done, and I'm just wishful thinking now.

Meh. This gives me a chance to tear the tranny and rear diff down. Call it educational. My dad would call it character building . Maybe it'll serve as a lesson to someone else, too.

I'm gonna park her for a few weeks, 'til the holiday season is over and the wife can get away for a few days. A three hour drive gets me to my sister's garage and the local Pick a Part yard; hopefully it'll hold together long enough to get me there. If not, I've got premium AAA (the one with 100 mile tow... so I gotta make it at least halfway ). I'll look for a '00-'04 5MT OBW, extra points if there's signs of a leaky headgasket (less likely that the used tranny is FUBAR). Finding a broken timing belt would be nice, too... isn't there an inspection cover I can pull real quick to look, without turning the engine over?

Anyhow, I'll swap the transmission and rear diff, then haul the old ones back up to my garage to pull apart at my leisure. It'll be interesting

[the_bard]

Hey... I got to thinking tonight (anyone smell the smoke? ), and I came across a thought which seemed blazingly obvious after the fact.

Since the noise is directly related to the vehicle's speed, and not the engine RPM, that pretty well guarantees it's the main shaft bearings, doesn't it? If it were the input shaft bearings, the noise would vary with engine RPM.

Not that it does me a bit of good right now, but I do feel better having come to that logical conclusion

Edit: I suppose it could be wear on the gear teeth, but only the final drive gear. If it were any of the first/second/etc. gears, then it'd only make noise in when the transmission is shifted into that gear.

Edited by the_bard, 07 December 2012 - 06:45 PM.
Added edit section.\

[Fairtax4me]

That thinkin' stuff is dangerous. :-P

You do have a point, and that's why I said its possible just the transfer bearings are damaged like GD said earlier in the thread. But with that much glitter floating around bearing damage can spread like cancer.
If the only noise is related to road speed its the output shaft bearings, transfer bearings or gears, or final drive (ring and pinion).
The mainshaft (input shaft on these) bearing will make noise relative only to engine speed.

[the_bard]

Ah. Mainshaft = input shaft. I thought the mainshaft referred to the output shaft. I learn something new every day. By the way, don't look up the Wikipedia article to find the definition of mainshaft: "Sometimes the term mainshaft refers to just the input shaft or just the output shaft, rather than the entire assembly." Like that clears anything up.

I should've mentioned that my thoughts the other day are directly related to how far I want to dig into that old transmission; I got the impression from a write-up somewhere that getting to the input shaft wasn't too bad of a job. That would imply that pulling the output shaft is going to be harder.