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Throwout bearing? Noise?



 
 
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  #1  
Old January 6th 05, 07:54 PM
ray
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Default Throwout bearing? Noise?

86 GMC S15 4x4, 2.8, 5 speed, 280,000km. (around 175,000 miles)

Owned it for 5 years, was stolen and the engine blown before I bought
it, so I don't know how old the clutch is. (don't know if the place
that swapped the engine did the clutch or not.)

I have a teeny hydraulic leak in the clutch somewhere - just a topup
about once a year... it's a winter truck. Sometimes in rush hour the
clutch pedal goes soft and you have to "pump it up..." which I was
figuring was the leak and/or the clutch just getting worn...

Anyway, new noise - a whump or a chuffing noise when shifting or
stopping. Thought it sounded like the clutch grabbing as it came up to
speed or something in the transfer case (it's noisy.)

What I've found is if I shift without using the clutch it doesn't make
the noise. If I shift slowly and into neutral between shifts and barely
touch the clutch it doesn't do it.

Is it possible for the throwout bearing to "vibrate" like a buzzing
sound? A clutch job would probably double the value of the truck, and
I'm hoping to milk one more winter out of it, but I really don't want to
totally destroy the thing either...

The clutch doesn't slip under hard acceleration, but with slippery roads
and a 2.8 there's no such thing as hard acceleration anyway. Sometimes
when stopping it'll do the same thing if you press the clutch down -
like it's not disengaging all the way - if you pop it into neutral the
noise stops.

I'm thinking throwout bearing is worn, or the slave cylinder is leaking
and not extending far enough and/or the clutch itself is worn.

Opinions? It's -30, so yanking the tranny out for a quick peek is
notgonnahappen... If it dies I go back to driving the wife's car until
spring.
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  #2  
Old January 6th 05, 08:49 PM
dcg
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Throwout bearing is usually pretty easy to isolate. Press the clutch
in.
If it makes a bounch of noise with the clutch pedal in, it's the
throw-out bearing.

If it makes noise without using the clutch, there is usually a bearing
in the rear of the crankshaft that the transmission shaft goes into..
This can be a bearing, can be a bushing - but when it fails the tranny
will tend to turn even with the clutch engaged and you'll get hard
shifts.

  #3  
Old January 6th 05, 09:52 PM
ray
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dcg wrote:
> Throwout bearing is usually pretty easy to isolate. Press the clutch
> in.
> If it makes a bounch of noise with the clutch pedal in, it's the
> throw-out bearing.
>
> If it makes noise without using the clutch, there is usually a bearing
> in the rear of the crankshaft that the transmission shaft goes into..
> This can be a bearing, can be a bushing - but when it fails the tranny
> will tend to turn even with the clutch engaged and you'll get hard
> shifts.
>


As long as I shift without using the clutch - no noise, no problem.
The noise is usually on the upshift when I let the clutch out.
But, I've had hard stops where I push the clutch in but don't move into
neutral and it's made the noise too.

I'm just in no rush to tear the whole thing apart on what would
otherwise be a disposable vehicle...
  #4  
Old January 6th 05, 10:09 PM
Brian
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Ray, you're describing a bad throw out bearing. It might be grouchy for a
few days, it might last a few months. I only ever had one fail, and it
lasted about three shifts from when it started grumbling, so you've already
beaten that...

Brian

Brian
"ray" > wrote in message
...
> dcg wrote:
>> Throwout bearing is usually pretty easy to isolate. Press the clutch
>> in.
>> If it makes a bounch of noise with the clutch pedal in, it's the
>> throw-out bearing.
>>
>> If it makes noise without using the clutch, there is usually a bearing
>> in the rear of the crankshaft that the transmission shaft goes into..
>> This can be a bearing, can be a bushing - but when it fails the tranny
>> will tend to turn even with the clutch engaged and you'll get hard
>> shifts.
>>

>
> As long as I shift without using the clutch - no noise, no problem.
> The noise is usually on the upshift when I let the clutch out.
> But, I've had hard stops where I push the clutch in but don't move into
> neutral and it's made the noise too.
>
> I'm just in no rush to tear the whole thing apart on what would otherwise
> be a disposable vehicle...



  #5  
Old January 6th 05, 10:47 PM
ray
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Default

Brian wrote:
> Ray, you're describing a bad throw out bearing. It might be grouchy for a
> few days, it might last a few months. I only ever had one fail, and it
> lasted about three shifts from when it started grumbling, so you've already
> beaten that...
>
> Brian
>


Well, I'm impressed I could diagnose it... but that sucks. I figured as
much... time to keep a screwdriver in the glovebox to take the plates off...
  #6  
Old January 7th 05, 02:03 AM
Anthony
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ray > wrote in
:


> The clutch doesn't slip under hard acceleration, but with slippery
> roads and a 2.8 there's no such thing as hard acceleration anyway.
> Sometimes when stopping it'll do the same thing if you press the
> clutch down - like it's not disengaging all the way - if you pop it
> into neutral the noise stops.
>


Here is the biggest clue, 'pop into neutral the noise stops'. This
sounds more like one of the input shaft bearings, or a pilot
bushing/bearing. You haven't changed anything to do with the throwout
bearing by shifting it to neutral, but you *have* disengaged the gears
in the transmission, and unloaded the input shaft. By shifting to
neutral, the input shaft is free to 'float' rotate with the engine,
which may even more point to a pilot bushing/bearing. The pilot probably
won't leave you on the side of the road, but it may eventually make the
truck jump like hell trying to engage the clutch. If it got bad enough,
I guess it *could* break the input shaft, but I've seen them completely
destroyed and the vehicle still drove, abiet roughly.




--
Anthony

You can't 'idiot proof' anything....every time you try, they just make
better idiots.

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  #7  
Old January 7th 05, 06:37 AM
Garrett Fulton
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"dcg" > wrote in message
oups.com...
> Throwout bearing is usually pretty easy to isolate. Press the clutch
> in.
> If it makes a bounch of noise with the clutch pedal in, it's the
> throw-out bearing.
>
> If it makes noise without using the clutch, there is usually a bearing
> in the rear of the crankshaft that the transmission shaft goes into..
> This can be a bearing, can be a bushing - but when it fails the tranny
> will tend to turn even with the clutch engaged and you'll get hard
> shifts.
>


I believe you mean that the trans. will tend to turn with the clutch
"disengaged" don't you? I've seen bad pilot bushings and bearings do that
very thing.

Garrett Fulton




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  #8  
Old January 7th 05, 07:48 AM
zork
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Default

Garrett Fulton wrote:
> "dcg" > wrote in message
> oups.com...
>
>>Throwout bearing is usually pretty easy to isolate. Press the clutch
>>in.
>>If it makes a bounch of noise with the clutch pedal in, it's the
>>throw-out bearing.
>>
>>If it makes noise without using the clutch, there is usually a bearing
>>in the rear of the crankshaft that the transmission shaft goes into..
>>This can be a bearing, can be a bushing - but when it fails the tranny
>>will tend to turn even with the clutch engaged and you'll get hard
>>shifts.
>>

>
>
> I believe you mean that the trans. will tend to turn with the clutch
> "disengaged" don't you? I've seen bad pilot bushings and bearings do that
> very thing.
>
> Garrett Fulton
>
>
>
>
> ----== Posted via Newsfeeds.Com - Unlimited-Uncensored-Secure Usenet News==----
> http://www.newsfeeds.com The #1 Newsgroup Service in the World! >100,000 Newsgroups
> ---= East/West-Coast Server Farms - Total Privacy via Encryption =---

well....throw it oUT!
 




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