1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Weird vibration

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Old Jun 26, 2007 | 05:49 PM
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From: Bellingham washington
Weird vibration

I have a engine vibration at 5000 to 5500 rpms. It happens in every gear and neutral -driving or not and over 5500 and it's smooth as silk up to the buzzer. Thinking carbon I tried seaform in the tank, full can in 1/4 tank drove 10-15 mile then filled up. I was thinking maybe the vacuum secondaries but the diaphram looked good- I wired the linkage to mechanical just to see but no change. The drive train is pretty much out because it does it sitting and driving. I'm stumped any ideas?
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Old Jun 26, 2007 | 07:53 PM
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you checked your ignition to make sure everything is up to par? plugs wires cap rotor?
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Old Jun 26, 2007 | 08:02 PM
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How are your engine mounts? Check them to see that they are not torn somewhere.
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Old Jun 26, 2007 | 08:06 PM
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How does your clutch feel? Last time it was replaced? Any slipping?
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Old Jun 26, 2007 | 08:30 PM
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Where is the vibration coming from?

I had some vibration over 5k rpm, coins in the tray between the seats whould shake. It was a bad transmission mount.
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Old Jun 26, 2007 | 09:48 PM
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Make sure that the exhaust system is not in contact with the frame. It must be isolated with rubber bushings, otherwise vibration. Otherwise my money is on the tranny mount...
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Old Jun 26, 2007 | 10:17 PM
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The motor mounts are fine, the exhaust is all rubber mounted, the ingnition is fairly new and it works good at other rpms. I havn't checked the tranny mounts tho. Would a tranny mount give a vib sitting in neutral? The clutch works good the throwout has a little howl since forever. I was thinking maybe the flywheel but the vib goes away above 5500 rpms. Thanks for the input all
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Old Jun 26, 2007 | 10:28 PM
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I forgot to mention the vibration seems to be in the engine or bell housing not the back of the car. I can stay below 5000 or above 5500 and the car is smooth and runs great, thats why I looked for carbon buildup or a flat spot between the primarys and secondaries first
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Old Jun 26, 2007 | 10:52 PM
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another vote for the transmission mount. tougher to diagnose than it is to replace, so may as well change it if it's old.
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Old Jun 26, 2007 | 11:00 PM
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From: Bellingham washington
Tranny mounts it will get, like you said they are old and due anyway. Thanks for the input, there's nothing like a weird noise to take the fun out of blasting around in a rx
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Old Jun 26, 2007 | 11:19 PM
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From: harrison, ar
This Is The Same Problem I Was Having!
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Old Jun 26, 2007 | 11:27 PM
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From: Bellingham washington
Was it tranny mounts on your car?
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Old Jun 26, 2007 | 11:31 PM
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From: harrison, ar
I Don't Know!
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Old Jun 26, 2007 | 11:54 PM
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From: Bellingham washington
I'll let you know if it helps
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Old Jun 26, 2007 | 11:58 PM
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Hopefully your clutch isn't falling apart... Or maybe lost an apex seal? Might want to perform a ghetto compression test on it to be sure.
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Old Jun 27, 2007 | 12:25 AM
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Originally Posted by budrud
Would a tranny mount give a vib sitting in neutral? The clutch works good the throwout has a little howl since forever. I was thinking maybe the flywheel but the vib goes away above 5500 rpms. Thanks for the input all
Yep, it will vibrate even when parked in neutral. Does it suddenly or gradually stop vibrating?

A bad tranny mount will seem like vibes are coming from the front of the car, since the mount is a bit ahead of the front seats.
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Old Jun 27, 2007 | 12:36 AM
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From: Bellingham washington
It suddenly stops vibrating, it's like a on off switch related to engine rpm
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Old Jul 1, 2007 | 12:52 AM
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From: harrison, ar
bump, i want to know what happend!
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Old Jul 1, 2007 | 01:02 AM
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From: Bellingham washington
I'm going to try replacing the tranny mounts. I'll let you know if it fixes it. I've tried everything I can think of and the car runs great.
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Old Jul 1, 2007 | 01:04 AM
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From: harrison, ar
cool.
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