strange noise after diff mount change and vcu fitted

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Gaj1612

Gaj1612

Active Member
Posts
246
hi,

hopefully someone on here can point me in the right direction.

recently fitted new vcu bearings, all 3 diff mounts and re fitted vcu and props.

think ive put it all together ok, but at low speed, theres like a rumbliing sound and it knocks a bit if i release the throttle quickly

is there any way the diff could be out of align? or maybe the vcu?

had a good look around it and cant find anythung that looks wrong.
 
Have you tightened everything up to the correct torques? The diff mounts only fit one way so I doubt you would have got them wrong. If it was UJs they would have been noticable before the change - unless they got a knock or a whack during dismounting.

Did you mark the exact location of the VCU carrier bolts before taking them off - the VCU must be at exact right angles to the prop. Try fiddling with the positioning a little. How much did you shift the diff - that too can go out of square. Might be worth loosening a bit and moving a touch.

Hope it helps!
 
Last edited:
I will definitely check everything over again later today
I've got another vcu and props here so if it doesn't work I'll try swapping them over
 
There is no need for the bearings to be perfectly aligned, just about square is fine.

Where is the VCU from?

Is you car an auto?

The knocking will probably be the rubbers in the carrier bearings being a bit too soft, we are seeing a few makes now where the rubber is too soft and when the throttle is let off the prop bangs against the metal rings on the supports. We have also seen some that are too stiff aswell, but these seem to give a vibration more than a bang, especially when turning.

The rumbling is probably the bearings themselves if they are the cheap ones. To be honest you cant tell if you are getting cheap bearings based on the price. I have tested and now sourced some good quality items which we now confidently supply with the VCUs.
 
Just been out in it now and it seems more of loud rumbling like something is vibrating against the body of the car. But if I press the clutch it disappears. Only does it under 1500 rpm
 
austen said:
There is no need for the bearings to be perfectly aligned, just about square is fine.

Where is the VCU from?

Is you car an auto?

The knocking will probably be the rubbers in the carrier bearings being a bit too soft, we are seeing a few makes now where the rubber is too soft and when the throttle is let off the prop bangs against the metal rings on the supports. We have also seen some that are too stiff aswell, but these seem to give a vibration more than a bang, especially when turning.

The rumbling is probably the bearings themselves if they are the cheap ones. To be honest you cant tell if you are getting cheap bearings based on the price. I have tested and now sourced some good quality items which we now confidently supply with the VCUs.
Click to expand...
Ok thanks for that it does knock if I let off throttle quickly but it is more of rumble as if something is vibrating against the body of the car.
 
Gaj1612 said:
Ok thanks for that it does knock if I let off throttle quickly but it is more of rumble as if something is vibrating against the body of the car.
Click to expand...

Try pulling the prop down see if you can make it push up against the bearing carrier, if you can do this easily then they are too soft. If the prop hardly moves then could be the rubbers are too hard.

How did you knock the bearings on?? Did you ensure you only knocked the inner part of the bearing which mates to the vcu, if you hit the outer part or the race you could have damaged the bearing itself
 
It doesnt do it in neutral at all. Only when in gear and under 1500 rpm. I I accelerate the noise disappears
 
Haven't had chance to have a look yet due to the rain but was wondering if it is the bearings. What are the best ones to replace them with
 
Ok so I've had a look today and the rubber mounts on the bearings are soft as ****. If I pull it it'll back on the bracket.
 
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