Vibration - Team Camaro Tech
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post #1 of 13 (permalink) Old Apr 26th, 01, 08:58 AM Thread Starter
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I recently installed a new motor, transmission, clutch and flywheel in my car. I have been trying to trace a vibration problem and have not found it. I am running a 383, weber clutch, 400 flywheel (externally balanced and a tremak 3550. The vibration shows up around 3K to 4K RPMs. YOu can feel it all over the car. The rear view mirror gets blurry when you use it and this rpm range. You an reporduce the problem with the cluth in and sitting still. I also have a little vibration in the cluth pedal.

All of this leads to flywheel/clutch right? I have checked the fuel pressure, valve springs, parts of the engine/tranny parts touching the frame. I have not ruled out exhaust resonance. I am running LT1 heads with 1 1/2 inch headers. They require 1 5/8 but I have been told this is not a problem. I am not sure what kind of mufflers are on the car. Could it be exhaust?

Is there a right way/wrong way to install an externally balanced flywheel?

Thanks Jeff
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post #2 of 13 (permalink) Old Apr 27th, 01, 04:19 AM
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Not sure about the manual trans flywheel but my 383 flex plate had a dowel pin hole and could go on only one way. You do have the pilot bearing pressed into the back of the crank - right? I've also heard of guys loosing counterweights - especially if one was added to a internally balanced flywheel (bad weld, etc.)

Either way if the vibration can be duplicated with the clutch pressed in then it has to be flywheel, pressure plate or engine - IMO. Would be surprised if it turns out to be exhaust.

Good luck.
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post #3 of 13 (permalink) Old Apr 28th, 01, 04:37 PM
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I assume you're using the external-balance 400 harmonic damper also (8" diameter, 1-1/2" thick, with a machined cutout along part of the rear of the outer surface)? Both this and the external-balance flywheel are required to balance a 400. If you've got the right balancer and flywheel (and the engine was balanced when it was built), I'd focus on the clutch - either have it balanced if you like the Weber, or pitch it and install a Centerforce.

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post #4 of 13 (permalink) Old Apr 28th, 01, 06:57 PM
 
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Another point of inspection is the harmonic dampner if you are using a used damp/balancer sometimes they will spin on the rubber cushion and there by changing the balnce point! also i'm sure during the assembly you checked the crank? i've seen brand new and freshly machined crank's that were bent or not true !

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post #5 of 13 (permalink) Old Apr 30th, 01, 05:41 AM Thread Starter
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Thanks for the replies. I lined up the dowel holes when I installed the flywheel. My flywheel does not have external weights on it. It is a GM performance parts flywheel. It looks like they add a section of extra metal during the machining process and then drill holes into it for the correct balancing. This was what I was told by the GM parts guys. I went back to them and we looked at a new 400 flywheel externally balanced and it was identical to mine. I have a new harmonic balancer. I am thinking clutch as well. My only issue that stops me from just diving into this is that the exhaust does not sound clean. Its hard to explain what I mean by this. I am wondering without knowing what kind of mufflers I have if they are to restrictive. I am also wondering since I have 1 1/2 inch header tubes if the restriction is causing some kind of turbulence that is creating an engine vibration or an exhaust vibration. I am thinking about ordering a set of 1 5/8 headers (since I need them anyways) and installing them before I rip the clutch out.

Another thought I have is that I am wondering if my thow out bearing is installed properly on the clutch fork. I had a friend helping me and I am wondering if he clipped it on to the fork or has the fork springs inside the throw out bearing groove. My clutch pedal has a slight vibration under heavy acceleration. I thought that this was due to not having a clutch spring installed on the fork. The engine seems to be running smooth under the hood (with my hand on the engine and rev-ing it) inside the car its a different story.
Thanks Jeff
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post #6 of 13 (permalink) Old Apr 30th, 01, 05:43 AM Thread Starter
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One more thing, I also have installed a new pilot bearing...

Jeff
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post #7 of 13 (permalink) Old Apr 30th, 01, 08:23 AM
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Jeff,

If it turns out to be the engine, let me know because I was thinking about getting an engine from the same guy who you got your engine from. Good luck.
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post #8 of 13 (permalink) Old May 2nd, 01, 01:58 PM Thread Starter
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I have pulled my transmission and bellhousing. My clutch fork and the bushing it floats on are really worn. One of my problems is that I get vibration into my clutch pedal. What sort of problems will a worn cluth fork cause? Could this be the source of my vibration. The clips on the end of the clutch fork are worn. One is worn off the other is still intact.

Where can I get a clutch fork and bushing? Will GM still be able to sell this to me or is this specific to my car?

Thanks Jeff
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post #9 of 13 (permalink) Old May 2nd, 01, 03:19 PM Thread Starter
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When I was checking out the pilot pushing with the clutch and pressure plate on I reached though the clutch disk and noticed that the center was loose. The center being the part that the input shaft slides through. I took the pressure plate off and examined the clutch disk. A few of the springs seems to rattle. The center spline on the clutch disk has some play in it. Is this normal?

Thanks Jeff
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post #10 of 13 (permalink) Old May 3rd, 01, 01:54 PM
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Your Chevy dealer can get the clutch fork and the pivot stud. Don't try to save the old fork - pitch it. When you install the (new) throwout bearing, remember that the fork AND the springs go INSIDE THE GROOVE in the bearing - I see them installed wrong all the time, with the curled ends of the spring capturing the flange on the back end of the bearing - result is inability to get correct clutch adjustment/free play.

I don't like the sound of your description of the condition of the clutch disc, either; Weber used to be big in the clutch business 30 years ago, but they aren't any more - hardly ever hear of a Weber clutch any more. If it was mine, I'd pitch the clutch and put a Centerforce in it; as you already know, this is not a fun job, and you only want to do it once.

You mentioned that you had a new balancer - is it the correct offset-weighted one for the 400? Any of them will fit, but only one is correct for your 400 crank.

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[This message has been edited by JohnZ (edited 05-03-2001).]
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post #11 of 13 (permalink) Old May 9th, 01, 03:57 PM Thread Starter
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Thanks for all the help. As suggested I have picked up a new Cenerforce Dual Friction Clutch. I was not happy with the movement in the clutch disc hub. The harmonic balancer and flywheel are the correct ones for my motor. When pulling the clutch fork out of the bellhousing I noticed that it had been repaired. Originally I thought it was a small crack. The repaired crack is fairly large. I have picked up a good used bellhousing. This weekend I will put things back together and keep my fingers crossed that my vibration is history.

Thanks Jeff
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post #12 of 13 (permalink) Old May 9th, 01, 04:49 PM
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keep us informmed on your vibration status post bell housing replacement.

good luck

joe c.
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post #13 of 13 (permalink) Old May 24th, 01, 04:29 PM Thread Starter
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Finally, I have good news. I got the car back together this evening and no more vibration. I ordered the Centerforce Clutch from gofastparts.com and it still has not arrived. I finally called Summit and they overnighted one to me this week. I ended up replacing the clutch with a centerforce dual friction clutch, the bellhousing, clutch fork, and all the pivots. Unfortunately, when I put the car back together this winter I did not notice that the old bellhousing was cracked. It did not become obvious until I removed the old clutch fork boot and fork. Once I saw the crack I looked really close and dicovered that it was cracked all the way from the clutch fork to the clutch fork pivot ball where it formed a V. The repair was quite good and it was sanded smooth on the flush part where the tranny mates against the bellhousing. I could only tell by looking at a porous line where it was welded. Its not clear if the problem was the clutch or the bellhousing but my money is on the bellhousing. Since my last clutch was new, I think that I may have had an alignment problem with the tranny due to the crack. This problem was a really hard problem for me to solve. I have so many new parts in the car from the mechanical overhaul this winter it made it difficult to isolate the problem. But, with the help from prior posts from other vibration problems and my own post I have the resolved the probem..

Thanks to everyone
Jeff
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