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[damon80]

Hi Folks,

I've noticed that at motorway speeds in my Miggy, when I lift off the accellerator, there's a grumbling noise.  Put my foot back down to accellerate, and it disappears.

Any ideas??

[Agemo]

Given the year, there should be nothing worn. How many miles has she done?

[damon80]

Done just over 100k

[Agemo]

Still would not expect problems.  Have you jacked it up & spun the wheels?  Could be a wheel bearing I suppose, Hope it's not gearbox.

[tunnie]

the noise from the front or back?

[damon80]

Jacked the back up, no play in any rear wheel bearings.

Noise seems to be coming from the back end.  I did suspect the diff, but I thought that if that was on the way out that it'd make a constant noise?

There's no noise whatsoever below 65mph...

[Andy B]

....
 I did suspect the diff, but I thought that if that was on the way out that it'd make a constant noise?

There's no noise whatsoever below 65mph...

Have you grabbed hld of the rear of the prop shaft to see if there's any play? My Senator's input shaft nut had backed of so there was a little play in the bearing. I could get it to grumble a it accelerated or slowed down, but if you accelerated enough to just take the weight off the bearing the noise disappeared. Just nipping up the bearing sorted it. If this is your problem don't go mad as there should be a specific preload on the bearing, worked out with rolling torque gauges (inches/lbs) etc that none of us have access to.

[damon80]

Cheers for the advice Andy - no, ain't tried that.  Will give it a go.

How much play is too much?  Because surely there should be a bit of play to allow for movement of suspension?

And correct me if I'm wrong - if it was a duffed diff, would the noise be constant, as oppose to the symptoms I'm getting?

[Andy B]

Cheers for the advice Andy - no, ain't tried that.  Will give it a go.

How much play is too much?  Because surely there should be a bit of play to allow for movement of suspension?

And correct me if I'm wrong - if it was a duffed diff, would the noise be constant, as oppose to the symptoms I'm getting?

You should just have a small amount of loading on the taper bearings on the input to the diff, and NO movement of the input shaft. It's unlikely that the diff will be shot so soon even if the input bearing is slightly slack. Have look at what moves on the suspension re the diff in put, the movement of the suspension doesn't have a bearing (no pun intended  ) on the diff input shaft. 

[Kevin Wood]

This might seem a silly suggestion, but is the exhaust system sound at the back end?

Chased such a rumbling myself for a while until the blow got a bit less subtle.

Kevin

[damon80]

Cheers for the advice Andy - no, ain't tried that.  Will give it a go.

How much play is too much?  Because surely there should be a bit of play to allow for movement of suspension?

And correct me if I'm wrong - if it was a duffed diff, would the noise be constant, as oppose to the symptoms I'm getting?

You should just have a small amount of loading on the taper bearings on the input to the diff, and NO movement of the input shaft. It's unlikely that the diff will be shot so soon even if the input bearing is slightly slack. Have look at what moves on the suspension re the diff in put, the movement of the suspension doesn't have a bearing (no pun intended  ) on the diff input shaft. 

Jeez, what's that in English, Andy??!!  Bearing in mind that I'm somewhat spanner-shy 

[damon80]

This might seem a silly suggestion, but is the exhaust system sound at the back end?

Chased such a rumbling myself for a while until the blow got a bit less subtle.

Kevin

Exhaust is getting ready for replacement tbh Kevin, but it's defo a mechanical sound as oppose to an exhaust blow.

Also, if I go over a bump on the motorway, when the load is taken off the suspension, the noise goes.  Once the suspension settles, back comes the noise...

[Pete Elite]

As Kevin suggested it may be a loose baffle in one of the exhaust boxes, try giving each box a thump with a clenched fist :-/.

[sassanach]

you haven't recently put any wanli ditchfinders tyres on by any chance?

[Andy B]

Cheers for the advice Andy - no, ain't tried that.  Will give it a go.

How much play is too much?  Because surely there should be a bit of play to allow for movement of suspension?

And correct me if I'm wrong - if it was a duffed diff, would the noise be constant, as oppose to the symptoms I'm getting?

You should just have a small amount of loading on the taper bearings on the input to the diff, and NO movement of the input shaft. It's unlikely that the diff will be shot so soon even if the input bearing is slightly slack. Have look at what moves on the suspension re the diff in put, the movement of the suspension doesn't have a bearing (no pun intended  ) on the diff input shaft. 

Jeez, what's that in English, Andy??!!  Bearing in mind that I'm somewhat spanner-shy 

If you remove the 3 bolts at the diff end of the prop shaft and swing it to one side you can see the nut holding the diff input flange in place. On my Senator this nut was loose, it shouldn't have been, but don't tighten any ,ore than a nip, otherwise you'll bugger the input shaft bearings up.     
Any better Damon?