Defender - slight vibration

[CAPP0]

Now before I start, of course we all know that all Defenders vibrate However, mine's got a new one.

Travelling at 50mph on a flat smooth road, I'm getting a cyclic vibration. It's pretty slight, not major, but definitely noticeable. It builds and drops over a 2-second cycle, then the next 2 seconds are smooth, then it builds and drops off again. Like this:


The amplitude isn't great, that diagram just represents the cyclic aspect.

Bit of background/history: about 2 weeks ago, MrsC was driving it when a youth slid his ancient Clio into the rear nearside wheel. I mentioned this on here when for asking tyre advice just afterwards. The Clio was travelling at probably <5mph, and whilst it tore the front off the Renault, the only apparent damage to the Defender was a slashed tyre sidewall. As a result, it's currently on the spare, because I've had real difficulty sourcing a replacement (got one tonight but it's on the wrong wheel). So I have 3 ATs and the temporary spare is an MT in the same size.

So, could it be:

1. the combination of the ATs and MT?
2. a wheel balance issue? I don't know whether the MT was/is balanced or not.
3. an unrelated wheel balance issue with one of the other wheels?
4. Something else entirely, either related to the knock or not?

I got underneath it just after it was knocked and I can't see any evidence of any damage whatsoever. Two other people have looked at it, one of whom repairs cars for a living and is a really good mech engineer, and they couldn't see anything either.

It's not anything daft like the CDL engaged (well, unless it has engaged without the knob being pulled and the dash lamp has also gone! Which was working a few weeks ago). For reference, it's running an RV8 with an LT95 box (with inbuilt transfer box) and a Fairey OD.

Any thoughts? When I get the tyre changed I'll get all 4 wheels checked for balance and see if it goes away, but if it doesn't I need to work out whether it's related to the knock or just pure coincidence.

Thanks.

[paintman]

Almost like something's winding up & then releasing?
2 seconds at 50 is quite a distance - around 45 yards.
I'd be inclined to jack the corner up & check that everything is free to rotate, the diffs are performing correctly and that the wheel is running true without any deviation (watch the tread as you rotate it)
Once you've got the new tyre fitted see what happens.

Edited by paintman on Sunday 18th December 21:59

[CAPP0]

I know what you mean about winding up and releasing - but this is almost somehow "softer"than that, if that makes sense? It really does gently build and recede, like the sine wave.

I probably won't be able to get the tyre changed until the week after Xmas, but it won't be going far between now and then.

[Dr_Rick]

My gut feeling is that it's a bearing issue: lateral tap to a wheel is not necessarily in the right plane for a bearing to be moving so one of the races might have moved out of line (or something).

[CAPP0]

That's a decent call, thanks. I'll jack it up and have a spin over the holidays.

[camel_landy]

FWIW - The bearings on the swivel-housing can cause odd vibrations when they go.

M

[LandRoverManiac]

CAPP0 said:

Now before I start, of course we all know that all Defenders vibrate However, mine's got a new one.

Travelling at 50mph on a flat smooth road, I'm getting a cyclic vibration. It's pretty slight, not major, but definitely noticeable. It builds and drops over a 2-second cycle, then the next 2 seconds are smooth, then it builds and drops off again. Like this:


The amplitude isn't great, that diagram just represents the cyclic aspect.

Bit of background/history: about 2 weeks ago, MrsC was driving it when a youth slid his ancient Clio into the rear nearside wheel. I mentioned this on here when for asking tyre advice just afterwards. The Clio was travelling at probably <5mph, and whilst it tore the front off the Renault, the only apparent damage to the Defender was a slashed tyre sidewall. As a result, it's currently on the spare, because I've had real difficulty sourcing a replacement (got one tonight but it's on the wrong wheel). So I have 3 ATs and the temporary spare is an MT in the same size.

So, could it be:

1. the combination of the ATs and MT?
2. a wheel balance issue? I don't know whether the MT was/is balanced or not.
3. an unrelated wheel balance issue with one of the other wheels?
4. Something else entirely, either related to the knock or not?

I got underneath it just after it was knocked and I can't see any evidence of any damage whatsoever. Two other people have looked at it, one of whom repairs cars for a living and is a really good mech engineer, and they couldn't see anything either.

It's not anything daft like the CDL engaged (well, unless it has engaged without the knob being pulled and the dash lamp has also gone! Which was working a few weeks ago). For reference, it's running an RV8 with an LT95 box (with inbuilt transfer box) and a Fairey OD.

Any thoughts? When I get the tyre changed I'll get all 4 wheels checked for balance and see if it goes away, but if it doesn't I need to work out whether it's related to the knock or just pure coincidence.

Thanks.

I had a similar thing a couple of weeks ago on the Disco.

It turned out that one of the wheel nuts was looser than the others - causing an ever so slight 'wobble' every 2nd time the wheel turned round. Turns out one of the threads had gone on the wheel nut and thus it never stayed 'tight' even when torqued up to the book value. Drove me nuts until I worked it out.

Does the vibration change/get worse/get better if you gently apply the brakes (if so - might be a warped disc or something along those lines). Does the rate of vibration alter with road speed - getting faster as you go faster, slower as you go slower, etc?

If you jack up each wheel in turn and rotate it by hand - see if you can feel any vibration as you do so.

Despite being the same 'size' the MT spare might be ever so slightly different in rolling diameter - so three wheels are effectively going at one speed and the forth is going either slightly quicker/slower.

The other other thing is possibly worn UJs / prop out of balance - possibly a slight 'wobble' along either the front or rear prop when it reaches a certain speed.

Those above noises tend to be shorter and sharper vibrations than this noise you're talking about - but it may be worth a look at these simpler things before going into wheel bearings, etc.

It could just be tyre tread rumble - but that is kind of a constant drone (as you probably already know) rather than a noise than comes and goes.

[CAPP0]

Thanks v much for this. It's only done about 15 miles this week, with MrsC at the helm, not me. Going to have another AT2 put on next week and we'll see what's what after that, but I do have plenty of potential sources now to investigate, so thanks to all who have given pointers. I'll try and remember to report back after!

[CAPP0]

Quick/final update - I'm now back on 4 x AT2s, all balanced up, and the vibration has gone So, it may have been a defective tyre, the tread mismatch, poor balancing on the spare wheel, or maybe even a slight kink on the spare. Whatever, all good once again. Cheers for all the input.