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Thumping in 3/4th gear.

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Old Jan 10, 2015 | 06:48 PM
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Exclamation Thumping in 3/4th gear.

Hello everyone, I've been coming to these Forums for a little over 6 months now mostly lurking and trying to find solutions for my problems. I must say, I'd be lost without this place lmao.

But I've ran into some issues shortly after replacing my Broken Tranny mount with an Energy Suspension one, I have a 1994 A4 Firebird Formula with the 3.24 Gearing and LT1 with 140k Miles. It's mostly stock except for little things like a MAF descreen, CAI, and Throttle Body.

Okay here's my issue: My acceleration is fine and the shifts are firm, but whenever I'm at about 60mph and push the Throttle in 40% or so I downshift from OD into 3rd gear, and then a deep Vibration out of hell comes from my console area, and gets worse the faster/more RPMs are on the engine. It's not a steady Vibration, but a Rhythmic THUMP THUMP THUMP THUMP that gets heavier and faster. The Thumping is about half a second in rhythm, and I feel like I'm losing power because of it. I haven't tried shifting into neutral when the thumping begins, but I will try that when it gets warmer haha I seem to notice the thumping even more-so during WOT but only in 3rd/4th gear.. And sometimes, the Vibrations are subtle where-as most of the time they're very violent.

Also, revving in Park or Neutral while not moving doesn't produce the vibration, so I don't think it could be Engine related.. I'm mostly thinking it's a Driveshaft or Tranny issue. I've had all my tires balanced and aligned, as well.

Could it be a bad pinion angle? I don't think it could be so deep and 'thumpy' to be that.

Anywho, thanks for reading! Just trying to get some clarification here

Last edited by FireBirt; Jan 10, 2015 at 09:51 PM.
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Old Jan 11, 2015 | 12:59 PM
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Put the factory mount back in and like magic it will be fixed.
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Old Jan 11, 2015 | 01:44 PM
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Originally Posted by RockinWs6
Put the factory mount back in and like magic it will be fixed.
Yeah I was contemplating doing that, but I keep tearing through rubber mounts haha

You know where I can pick up a stock 1LE rubber mount?
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Old Jan 11, 2015 | 02:15 PM
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Well the factory mount is hiding the problem, that's why the factory uses um.... Good Luck
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Old Jan 11, 2015 | 02:22 PM
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You could try indexing the drive shaft 180, then drive it and see how it feels. Or add a washer or 2 under the mount to change the angle of the drive shaft.
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