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73-87 Chevy _ GMC Trucks => Engine/Drivetrain => Topic started by: JAH on March 25, 2020, 11:01:47 PM
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One of my trucks (Rico) is a 1986 K30 4X4 regular cab dually, with the LE8 454 and SM465 transmission.
Today, we got out to run some "essential" errands. And, while sitting in the drive-thru at CVS, I noted some very pronounced clattering or chattering coming from the underside of the truck. The tranny was in neutral with my foot off the clutch. The clattering seemed to affect the idle, just a bit, making it slightly rough.
When I would depress the clutch, the clattering would stop.
The driving experience wasn't much different than normal, other than the idle.
[***A bit of a disclaimer- The transmission was pulled and rebuilt, a couple of months back. The clutch (and, supposedly, the throw-out bearing) was replaced.]
I found nothing thru the Google, and am at a loss. Any ideas?...
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Can you post a sound clip?
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Can you post a sound clip?
Rich, I absolutely love your posts. I read through your stuff all the time.
I would love to post a clip for you. Unfortunately, I have no photo hosting site, and don't think I could get one to fit in the designated amount of bytes. I have a YouTube account, but am too much of a luddite to know how to get something to you in that format.
Sorry.
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Just a thought... Is the fluid level in your transmission ok? Was the proper weight oil used in the transmission?
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My guess? A spring on the clutch disc or pressure plate gave up the ghost.
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I haven't personally checked the fluid level, but am about 90% sure it's not a fluid level or weight issue. I may crack the fill plug tonight and have a look-see (as far as the level), just to be safe.
Because of the recent tranny overhaul, and the repair/replacement of so many goodies, I'm thinking that the "spring" explanation makes the most sense. I've had "new" components sh__ the bed before. While it's not common, it is definitely a possibility. The nice thing about being not-so-mechanically-inclined, and having to pay for larger jobs, is that...whatever it is...it'll be someone else's issue to fix.
Thanks for the responses.
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Thoughts on springs the centrifugal force spinning in neutral shouldn't make any noise, only when the clutch is in and the transmission it not spinning. Do you have any free play in the pedal where the throw out bearing isn't touching?
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I had the same problem some time ago and my spring on my clutch fork was bad and it was loose, causing the bearing to rattle while the engine was running. When I pressed the clutch peddle in, it would stop. Replaced the spring and adjusted the clutch and everything was OK.
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Thoughts on springs the centrifugal force spinning in neutral shouldn't make any noise, only when the clutch is in and the transmission it not spinning. Do you have any free play in the pedal where the throw out bearing isn't touching?
Carl, I didn't ignore your post. I just haven't checked the free play yet.
I will tell you that everything was copacetic...until it wasn't. The tranny felt smooth at operating temp, and the clutch felt nice and firm, but not overly so (if that makes any sense).
I had the same problem some time ago and my spring on my clutch fork was bad and it was loose, causing the bearing to rattle while the engine was running. When I pressed the clutch peddle in, it would stop. Replaced the spring and adjusted the clutch and everything was OK.
Thanks for the post, Mike. As I mentioned, the whole "spring" thing sounds like the most logical explanation. :(
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Way back when I bought my '74 stepside with the SM465, it had virtually the same exact symptom you described. Guy wasn't a mechanic, he thought the whole thing was knackered, which is why I only paid $500 for it.
Got it home, pulled the tranny. The throwout bearing had somehow seized itself on the input shaft, and ripped itself into two pieces - the other of which was sort of bouncing up and down the shaft. Was only quiet when pedal was pressed and clutch engaged. Wish I had taken pictures at the time, it was something. My guess is that your throwout bearing did get changed, but they installed it on the shaft dry, and now it's come apart.
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Since it's tough to find a quality replacement bearing nowadays, look for a Japanese one...(Koyo). All of the manufacturers that used to make U.S.A. made bearings have been sent overseas. :-\
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I got Rico up on the trailer, yesterday, and got him to the guy who pulled the tranny for the rebuild. I did confirm that the throw-out was not installed dry.
Funny thing is, during the warm-up of the truck, there was no clattering. When I got him off the trailer, I did a few hot laps around the block, and still...nothing. I can't tell y'all how much I love this kinda' stuff. ( <--- Sarcasm, in case you didn't know )
Give me a second to shake my magic 8-ball...
Me- "Magic 8-ball, will this turn-out to be one of those instances where the Mechanic is 'not able to duplicate' the problem, only to have it miraculously re-appear when I'm all alone out in BFE, and the tow will cost me $300?"
Magic 8-ball- "It is certain."
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