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#1
06-26-2020, 10:45 PM
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Banging noise from front universal joint
I have a 72 gto clone with a 3 speed transmission, been working on it for almost 10 years, took it on the road today, and gunned it in first gear, and heard a banging noise coming from transmission tunnel. Sounds like someone banging on the tunnel with a hammer. New: motor mounts, trans mounts,universal joints, crossmember mounts.. ,only does it when hitting the gas hard., driving easy, nothing. I replaced floor pans,but have plenty of clearance. What would be causing this? Thanks.
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#2
06-26-2020, 11:03 PM
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Exhaust pipes hitting something?
Engine torques over under load, uses-up all the clearance as it tilts on the mounts? |
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#3
06-27-2020, 12:30 AM
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Probabl;y right about the engine torquing over.
My guess would be that the front universal trunnion / yoke is hitting the floor.
Current production trans mounts are too tall - there's not very much clearance. Look for marks on the trunnion / yoke and the floorboards. Good luck! |
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#4
06-27-2020, 01:06 AM
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Found Mark's on transmission tunnel, I was able to to push up on driveshaft at yoke,lifting transmission slightly. Removed transmission mount, (rubber).I installed it many years ago, should I go with a solid mount? So I have no movement, urethane mounts on the motor.
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#5
06-27-2020, 02:32 AM
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I'd use a mount with some flex in it.
I've heard that some have had issues using the solid mounts.
Glad you found the problem easily. 
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#6
06-27-2020, 10:12 AM
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I'd be lowering the transmission mount by modification of it, or finding a shorter one. It's been brought up before on this forum that some of the newer transmission mounts are too tall pushing the tailshaft and driveshaft up into the tunnel.
You might want to look at the transmission crossmember for problems on the rubber isolators too. They have a habit of filling up with road salt and dirt and rusting the ends off of the crossmember allowing the left side to lift up from the frame rails under acceleration. A turnbuckle attached to the left cylinder head and the frame, and is adjustable. It will limit engine movement without resorting to solid mounts due to possible failures of the block bulkheads where the mounts are attached. I myself won't use solid mounts, but that's completely your call.
__________________
Brad Yost 1973 T/A (SOLD) 2005 GTO 1984 Grand Prix 100% Pontiacs in my driveway!!! What's in your driveway? If you don't take some of the RACETRACK home with you, Ya got cheated    
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#7
06-27-2020, 11:41 AM
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Pretty common for the ends of the crossmember to be bent from someone using a floor jack under the center of crossmember to raise the car up. This can cause the clearance issues like you have. Sometimes the frame is bent upward at the crossmember attach point also.
http://forums.maxperformanceinc.com/...54#post5928354
__________________
 66 GTO, 495, M22, Strange S-60 w/4.10 Sold new at Ace Wilson's Royal Pontiac http://www.youtube.com/watch?v=cUHC-Z8xhtg |
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#8
06-27-2020, 02:32 PM
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Also the engine mounts could be worn out too, same thing happened to my 66 GTO way back ...
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