I'm huming....

Raised this in another thread, and seeking advise what it might be. 3 door 2004 TD4. Rear diff was replaced with a 2nd hand serviced unit,new carrier Bearings on the drive shaft.

When driving there is a hum, but clutch or take out of gear and free wheel, the Hum goes away.. hum seems to be from either centre of car or to rear.

Basically would diff or carrier Bearings stop huming if freewheeling and out of gear.?

Thanks

Possible that something like the diff hums under load then stops when you declutch but usually more of a whine.

Underbody microphones are good for this type of noise. 4 mics, switch box, headphones, switch to hear loudest.

If it is load related then dropping prop off will not help.
If centre of car, then worth dropping 4 bolts out on vcu bearings and prop drops slightly. You can then spin them on the prop and listen. Easy and cheap to do.
Also, sit someone in the rear load space and get them to listen !!

Alex1000 said:

Basically would diff or carrier Bearings stop huming if freewheeling and out of gear.?

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Are the bearings perfectly parallel to each other, and both exactly 90° to the VCU shaft?

Nodge68 said:

Are the bearings perfectly parallel to each other, and both exactly 90° to the VCU shaft?

Click to expand...

Was done by a garage that should have, but I'll get her over the pit at work and check...annoying as diff and carrier bearing were done and seems to be coming from one or the other..but if clutched and free wheeling would they not still hum?

Idea.
When my vcu bearing was getting noisey, the noise changed and got worse when turning a corner.
Presume this changed the loading and put more strain on prop and all.

Try turning left and right whilst listening.

Did that. No noticible difference with hum. Am getting a scobing from front wheels, when I turn, that I'm sure are brake calipers binding, but that's next week's posts....

Appreciate I bought the car 3 1/2 years ago, and only did the work for MoT in September, and in turn only put her on road at start of January.. so with her sitting so long, miracle that's all that is huming, what ever it is..

Do plan next weekend to strip all brakes and grease the slider pins and check rear shoes..and fix aerial, replace rear brake light switch, fit new master clutch servo, fit crank case breather. Kit...that's next weekend fubar.....but this hum is annoying me....

Alex1000 said:

Am getting a scobing from front wheels, when I turn, that I'm sure are brake calipers binding, but that's next week's posts.

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Has it got identical tyres front and back, with the least worn on the rear?

I splurged out when I did the work to her. All brand new tyres front and rear. Only 200 mile done since mot. And at 28 to the gallon, might not be a lot more. My 308 estate is doing 65...filling the hippo hurts like feck....

28mpg is not unexpected for an auto round town. On a run you should see 35+ I'd have thought.

Transmission noises on Freelander can be really difficult to diagnose. Step 1 I'd have thought would be to do a 1 wheel up test to make sure the vcu isn't knackered. Its a relatively quick and easy check that doesn't cost anything but can highlight a serious issue. If the vcu is knackered then anything else you do may be ruined very quickly. I'd especially recommend that if the diff was knackered. They don't generally fail for no reason and the IRD may be next!

I'd also change the oil in the ird to make sure it does not have a metallicy sheen to it. That will be the bearings ground to a pulp and impending doom.

You could try removing the props and driving it to see if the hum goes away. Its not a guaranteed identifier of a fault but may rule out things such as carrier bearings. Once again a no cost test.

Thanks, but new carrier Bearings just fitted, and a replacement diff that was checked and serviced by an engineering works/gearbox specialist.. The VCU check I'm going to get done tomorrow at work garage.. and I'm a manual box, is 28 mpg normal for a 2.00 lt td4..?..would a defective vcu hum,? IrD I will pick up oil and do an oil change, and check what comes out...but hum seems more to back of vehicle.

Alex1000 said:

Thanks, but new carrier Bearings just fitted, and a replacement diff that was checked and serviced by an engineering works/gearbox specialist.. The VCU check I'm going to get done tomorrow at work garage.. and I'm a manual box, is 28 mpg normal for a 2.00 lt td4..?..would a defective vcu hum,? IrD I will pick up oil and do an oil change, and check what comes out...but hum seems more to back of vehicle.

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I would not expect my L Series to drop below 30mpg in town - but then my in town may be less congested than yours. On a run it pushes 40mpg. I believe the TD4 is pretty similar. Its the autos that can consume more fuel in town driving.

The VCU, defective or otherwise, will not make any noise I don't think - mine didn't before it trashed the IRD. It will also usually look good as new on the outside. You really can't tell what condition its in without testing it.

I wouldn't necessarily trust new items to not be faulty - or even installed incorrectly if people don't have good knowledge of Freelander - as described above. An experienced gearbox shop should be able to tell if a diff is in decent condition though if they have inspected it. I presume it was installed with new mounts/bushes. Worn mounts generally create knocking rather than humming.

Yup, she got all new rear diff mounts.

Work done 8n September was

Full service, Inc all filters
2 new front wishbones
Replaced rear diff
All new diff mounts
New carrier brackets for fuel tank
REAR WINDOW REGULATOR replaced
Rear door opening issue fixed
New Carrier Bearings for drive shaft/ VCU
All new tyres front and rear.

FOLLOWING TO DO
Replace/fix reversing lights switch
FIT NEW AERIAL
Fit the crank case filter upgrade.
Test VCU
Find out what the hell the hum is.
FIT clutch master servo.
Check and service brakes front and rear. Grease sliders.

Alex1000 said:

The VCU check I'm going to get done tomorrow at work garage

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I wouldn't expect a normal garage to be able to check a VCU, or even understand what it's supposed to be doing.
The only true way to check it is in a 10 HP lathe which can spin one end at a certain RPM, while the other end is held still and the torque measured.

The One Wheel Up Test sort of emulates the official test, but can be done at home with minimal equipment.

MPG on a TD4 manual should be mid 30s. If not then it's worth checking the CAT for restrictions in the matrix.

Thanks, its the one wheel up test I'll be doing

Hi,

For the huming sound, if there is not sound in free wheel, it could be a transmission bearing.
Personnaly I will start by changing the gearbox oil if it's never be done ...

Huming sound comming from the center of the car, it's more probably cheap vcu bearings, they are always noisy.

But do vcu Bearings stop humming when clutch or out of gear...

Alex1000 said:

But do vcu Bearings stop humming when clutch or out of gear...

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They would definitely be less likely to - but the forces going through the transmission would change between accelerating and coasting - so it is possible.

Alex1000 said:

But do vcu Bearings stop humming when clutch or out of gear...

Click to expand...

Don't forget that the engine will move on its mounts between drive and coasting, especially so if the lower tie bar (often called a torque bar) bushes have gone soft.

Came across this

http://www.myfreelander.co.uk/Transmission/fdprobs4.htm

Seems that 2002 and before Freelander Diffs had a problem, and landrover changed the design. Now I'm worried the replacement diff I fitted was the older type. This is probably old news to most of you on here, but is there a way to tell the difference between a diff before and after 2002. I might have to change my diff if the hum is it (And it looks more and more like it is. Not using that engineering company again..

And I really love that Landrover allocated 9/10ths of an hour to replace a rear diff....