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Joined: Jan 2021
Posts: 70
Just Getting Started
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OP
Just Getting Started
Joined: Jan 2021
Posts: 70 |
Hi all,
(New here but loving this forum)
Driving my new M3W today on its first drive (with the exception of taking it home last week) and at one point I put the pedal hard down. I immediately felt a violent and very loud BANG-BANG-BANG. It sounded very destructive and I was sure the driveshaft had come loose or something. It does it in lower gears, the lower the gear the more violent it is. It sounds and feels like someone is hitting the underside of the car with the sledge hammer. Feels like it’s coming from the tunnel area. Anything up to about 75% throttle the car is fine though.
I can’t for the life of me work out what could cause this (I’ve built cars from scratch but the M3W certainly has some bits I’m not familiar with!). I’ve not found anything searching. Has anyone seen this issue before?
Thanks,
Greg
Last edited by GregA10; 14/02/21 07:54 PM.
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Joined: Oct 2012
Posts: 2,776 Likes: 59
Talk Morgan Expert
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Talk Morgan Expert
Joined: Oct 2012
Posts: 2,776 Likes: 59 |
Probably the drive belt is needing tightening. They do need to run quite tight and once adjusted the rear wheel spindle needs done up pretty damn tight to keep the wheel where it should be and to keep the belt tight. And welcome to the strange world of there daft little cars!
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Joined: Jan 2021
Posts: 70
Just Getting Started
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OP
Just Getting Started
Joined: Jan 2021
Posts: 70 |
Probably the drive belt is needing tightening. They do need to run quite tight and once adjusted the rear wheel spindle needs done up pretty damn tight to keep the wheel where it should be and to keep the belt tight. And welcome to the strange world of there daft little cars! Ah you see! Never dealt with belts or bevel boxes! So are you saying the belt may be slipping and sending a shock to the bevel box making it buck into the chassis? That would be a wonderfully simple and easy to fix issue then. Comforting! 🤞🏻 Thanks
Last edited by GregA10; 14/02/21 08:07 PM.
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Joined: May 2011
Posts: 1,613 Likes: 22
Talk Morgan Enthusiast
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Talk Morgan Enthusiast
Joined: May 2011
Posts: 1,613 Likes: 22 |
The NVH kit the bevel box is mounted on can make the noise you describe under very hard acceleration, as it is mounted on metalastic bushes which allows it to move, with this arrangement the belt needs to be tighter than you might expect. An alternative solution is to replace the NVH kit with Phil Bleazey's bevel box mount which bolts the bevel box solidly to the chassis.
2021 M3W 2013 M3W - Sold 1971 4/4 2 Seater 1934 Sports
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Joined: Feb 2019
Posts: 3,854 Likes: 2
Talk Morgan Addict
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Talk Morgan Addict
Joined: Feb 2019
Posts: 3,854 Likes: 2 |
Calum has a good suggestion and would be my first place to look. The NVH also does move, particularly once they get broken in or with age and as it moves it seems to change belt tightness under torque.
The light at the end of the tunnel is actually a train. 2019 M3W
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Joined: Jan 2021
Posts: 70
Just Getting Started
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OP
Just Getting Started
Joined: Jan 2021
Posts: 70 |
Thanks all!
I’ve been doing tons of research over the last few months and have become familiar with Phil’s modifications. I did also see that of all the technical improvements done to the M3W over the years the rubber NVH bevel mounts were the only thing that people considered a downgrade. I’ll have the belt tightened for now under warranty/service but I see Phil’s kit in my future!
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Joined: Nov 2018
Posts: 6,056 Likes: 160
Talk Morgan Sage
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Talk Morgan Sage
Joined: Nov 2018
Posts: 6,056 Likes: 160 |
I saw on the other thread there was talk of a rev limiter - you're not hitting that are you?
1972 4/4 4 seater, 1981 MGB GT 1984 Harley Davidson Electra Glide, 1990 Kawasaki ZX10
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Joined: Dec 2017
Posts: 2,041 Likes: 71
Talk Morgan Expert
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Talk Morgan Expert
Joined: Dec 2017
Posts: 2,041 Likes: 71 |
If it is a brand new M3W and you have just started driving it I hope you are following the break-in procedures, otherwise you could be doing more damage!!!!
Bruce 1964 4/4 Series V Comp (Megan) 1994 +8 (Maurice) 2013 M3W (Olga)
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Joined: Jul 2013
Posts: 3,658 Likes: 48
Talk Morgan Addict
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Talk Morgan Addict
Joined: Jul 2013
Posts: 3,658 Likes: 48 |
I saw on the other thread there was talk of a rev limiter - you're not hitting that are you? It's quite a soft rev limiter if/when you hit it and is very unlikely to casue the violent banging. 99.9% the bevel box moving so, as above, first tighten the belt and then maybe consider Phil's upgraded mounting. As a quick check - you should only be able to twist the lower run of the drive belt about 45 degrees or slightly over.
Red Leader
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Joined: Nov 2018
Posts: 6,056 Likes: 160
Talk Morgan Sage
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Talk Morgan Sage
Joined: Nov 2018
Posts: 6,056 Likes: 160 |
I saw on the other thread there was talk of a rev limiter - you're not hitting that are you? It's quite a soft rev limiter if/when you hit it and is very unlikely to casue the violent banging. That's good, some of the 'bike' ones just cut the ignition when you hit it, leading to an almighty racket!
1972 4/4 4 seater, 1981 MGB GT 1984 Harley Davidson Electra Glide, 1990 Kawasaki ZX10
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