Road vibration under power
Thread Starter
Racer
Joined: Sep 2011
Posts: 414
Likes: 55
From: Humboldt county Ca
Road vibration under power
Installed a new 383 in the '75. Has a turbo 400 trans. At between 55-70 mph a vibration starts but the origin is hard to pinpoint, almost feels like a wheel in front out of balance. Slip it into neutral at the same speed and RPM and the vibration stops. Let off on the throttle at speed and the vibration stops. All 4 wheels just aligned and tires balanced after strut rod bushing replacement. New torque converter installed with engine (Continental, from SoCal) and new motor mounts.
Thoughts please.
Stump
Thoughts please.
Stump
2nd Gear
Joined: May 2016
Posts: 2
Likes: 0
Installed a new 383 in the '75. Has a turbo 400 trans. At between 55-70 mph a vibration starts but the origin is hard to pinpoint, almost feels like a wheel in front out of balance. Slip it into neutral at the same speed and RPM and the vibration stops. Let off on the throttle at speed and the vibration stops. All 4 wheels just aligned and tires balanced after strut rod bushing replacement. New torque converter installed with engine (Continental, from SoCal) and new motor mounts.
Thoughts please.
Stump
Thoughts please.
Stump
If your 383" doesn't have a 400" damper and flex plate it will vibrate.
Pro
Joined: Oct 2009
Posts: 664
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From: Marysville Ohio
Thread Starter
Racer
Joined: Sep 2011
Posts: 414
Likes: 55
From: Humboldt county Ca
Race Director
Joined: May 2006
Posts: 18,737
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you didnt specify the RPM but can you replicate the vibration by having someone hold the engine at that speed and checking your pulleys, belts, and fan.
the engine fan/clutch assembly is properly seated on the water pump pilot?
if you are running vacuum advance, disconnect it and plug the line and drive it. If the vibration goes away you have a timing related issue.
the engine fan/clutch assembly is properly seated on the water pump pilot?
if you are running vacuum advance, disconnect it and plug the line and drive it. If the vibration goes away you have a timing related issue.
Is my vette stock?? HAHA
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From: Im not allowed to tell you
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Check the u joints. If you're loosing one all that mass under power will move and as soon as you ket up it calms down.
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Thread Starter
Racer
Joined: Sep 2011
Posts: 414
Likes: 55
From: Humboldt county Ca
Thanks to all for the thoughts. I'm thinking u joints also. The engine is 370 hp with 450 lb/ft of torque @3600. I confess to hammering the 90,000 mile u joints just a wee bit. Think I'll replace them all.
Thanks again!
Thanks again!
Melting Slicks
Joined: May 2011
Posts: 2,753
Likes: 119
From: Springfield Missouri
he puts in neutral, and the vibration stops, so it would point to the engine?? rpm goes down and vibration goes away. BUT engine was dyno tested, but not hooked up to a transmission, etc., so ???
Last edited by lvmyvt76; May 6, 2016 at 11:18 PM.
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From: New Or-leens Loo-z-anna
The bearing "cups" should be a tight fit into the mating holes in the yoke.
If the bearing "cup" slides into the yoke hole easily, the hole has probably stretched oversize which will cause the bearing cup/needle-bearings to fail much sooner.