Vibration at 55 mph

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Dixie6789
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Vibration at 55 mph

Post by Dixie6789 »

Has anyone ever had a gearbox (LT 77)vibrate at a given speed.

My Cobra has developed an unusual vibration, but only at 55 mph, no other speed.
Wheel bearings are ok. Feels like it's coming from under my bottom when sat in seat.
I have greased the UJ'S on the prop. But not taken out to physically check if stiff.
Box works fine,changes gear easily, I have just refilled with correct oil.
May gland get rear wheels balanced just to rule it out.

I guess I just need to rule one thing out after another which will hopefully leave the culprit.

Thanks Mark.


Mark

Spongo
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Post by Spongo »

Does it happen at the same speed in any gear? If so it pretty much rules out the gearbox, sounds like a prop shaft UJ or maybe a balance weight has come off of the prop shaft.
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Dixie6789
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Post by Dixie6789 »

Thanks for the advice.
Happens in 4th or 5th at 55 mph.
Will drop the prop off to check UJ's.
Will also see if there is a local place that can check balance.
Has only just happened.

Mark.
Mark

scudderfish
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Post by scudderfish »

If you put the car in neutral and coast does it still happen?

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Ian Anderson
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Post by Ian Anderson »

Are your UJ's set up correctly.

If in phase they can cause this problem.
Have a read on threads like this
http://www.locostbuilders.co.uk/viewthr ... tid=186232

Or
You could have a tyre out of round, flat spot from sitting for a long period or delaminating after hitting a curb / pothole etc.

Ian
Owner of an "On the Road" GT40 Replica by DAX powered by 3.9Hotwre Efi, worked over by DJ Motors. EFi Working but still does some kangaroo at low revs (Damn the speed limits) In to paint shop 18/03/08.

DEVONMAN
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Post by DEVONMAN »

Half Shaft UJ on jag axle could cause this.
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Been as far as the Moon and back in 57 years of driving. Same Car, 5 engine upgrades !!!


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JSF55
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Post by JSF55 »

Check the phasing of the jag rear u/j's to. I've done enough burnouts to put mine 90o out :shock:
So thats where it went !

Dixie6789
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Post by Dixie6789 »

Update.

It was a faulty rear wheel bearing in the Jag hub. Sent to Wards for refurb.

Mark
Mark

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