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Vibration but only when under load
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Author:  misterp [ Sun Nov 20, 2016 11:55 am ]
Post subject:  Vibration but only when under load
The car must have heard me say to someone today "its great, drives lovely" as no sooner had I got home, it developed what I think is a vibration.

I say think as at first I thought it felt like a mis-fire on the engine, but after a bit of driving, Im fairly certain its a drive-line vibration as the engine is smooth at idle, and icks up and drives through the rev range with no noticeable lag.

So..I shot some grease into the rear axle bearings and propshaft bearings and gave the prop a wiggle and noticed a fair bit of play in the centre bearing.
"That`ll be why I get a bit of judder when I take off" I thought.

Now, driving along at any speed, when accelerating, I get the judder/grumbling and yet when I back off the acceleration, the vibration disappears.
Judder increases with road speed as well.

Best way I can describe it is rather than the smooth surge it had before, it feels like a tuned MG B series engine..gruff almost (rubbish description but best I can do)

Time for a new centre bearing or something else?

Any suggestions? (remembering Soe8m's pic....diagnosis from the internet = hard) but appreciate any knowledge on how the centre bearing goes, and what it feels like when does go?

Thanks

Andrew
Author:  tony g [ Sun Nov 20, 2016 12:34 pm ]
Post subject:  Re: Vibration but only when under load
Its worth checking the gearbox mount. If its gone a bit soggy or even detached from the rubber it can cause the tail of the box to lift slightly (under load) and change the angle in the prop u/j's, which can give a vibe.

Tony
Author:  xvivalve [ Sun Nov 20, 2016 12:49 pm ]
Post subject:  Re: Vibration but only when under load
If the centre bearing is shot or on it's way out, you will see that the rubber annulus that suspends the middle of the prop is ripped/torn/missing
Author:  Carledo [ Sun Nov 20, 2016 12:55 pm ]
Post subject:  Re: Vibration but only when under load
Normally the bearing will not give trouble until it is visibly badly torn. They have quite a bit of wiggle in them even when new.

As Tony said, check the gearbox mount carefully and also check for axial movement in the front and rear prop U/Js and check the rear wheel bearings before condemning the centre bearing.

Steve
Author:  Jon Tilson [ Sun Nov 20, 2016 5:51 pm ]
Post subject:  Re: Vibration but only when under load
I have only ever had driveline vibration on an 1850 when the rear propshaft u-j is on the way out. It starts at about 45 mph and then gets
worse and comes in at lower speeds.

First place I would look but it needs a big screwdriver to lever on the propshaft yoke to see any movement. The slightest sign and that will be it...

Jonners
Author:  misterp [ Mon Nov 21, 2016 10:00 am ]
Post subject:  Re: Vibration but only when under load
Thanks for the replies gents,

Interestingly enough I had the mount off as I needed to get to the O/D solenoid and give it a clean out (fingers crossed cleaning and replacing the O-rings will cure the intermittent 1/2 engaged O/D that I get sometimes when the oil is warm)

I`ll check that Ive re-fitted the mount properly before doing anything else.

Strange thing is that it does the grumbling from standstill to 110+ Kph with varying frequency.

More things to check when Im next underneath it.

Thanks once again.
Author:  dailysprinter [ Sun Nov 27, 2016 5:45 pm ]
Post subject:  Re: Vibration but only when under load
Don't just check gearbox mount, just as likely to be a knackered engine mount, allowing engine to hit steering rack under acceleration. I've had it personally, it does feel & sound terminal but it's not.
Author:  misterp [ Thu Dec 29, 2016 6:45 am ]
Post subject:  Re: Vibration but only when under load
Quote:
Its worth checking the gearbox mount. If its gone a bit soggy or even detached from the rubber it can cause the tail of the box to lift slightly (under load) and change the angle in the prop u/j's, which can give a vibe.

Tony
For completeness, Tony above was spot on and whilst the mount was OK...I had mounted it the wrong way up. :oops:

Amazing the difference the mount either way up can make to the whole feel of the car, as it made it seem like the engine was missing and lumpy, yet it wasnt a huge out of balance wobble that you might experience if say the tailshaft UJ's are on their way out.

Either way..thanks Tony for the spot on advise.

Andrew
Author:  tony g [ Thu Dec 29, 2016 7:41 am ]
Post subject:  Re: Vibration but only when under load
Glad to help Andrew, great to have it sorted :thumbsup:

Tony
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