transmission banging

[Nicholas Lewin]

I have my lovely 240 estate back as of today and she is stopping much better than she was - thank gawd for that!

But, you know what, there's still some grumbling going on under the floor...

Here's the history as brief as I can:
1 Bought at 98k miles - transmission smooth as you like in all aspects except a weird vibration in top gear 45-60mph. No clutch judder and no banging
2 2nd hand g/box fitted and clutch changed. Much vibration. Undriveable
3 f/wheel skimmed (allegedly burned). Better but still bangy
4 use car. Banging gets better
5 original g/box vibration investigated - turns out to be shagged main shaft/top gear - so a genuine fault (but no longer relevant)
6 car still banging (low speeds - especially reversing)
7 s/h (111k mile) propshaft fitted. Better but still bangy

So what's the deal? It's had new suspension bushes all round (3 months ago). The clutch itself new 18 months ago

Possible centre bearing on prop? Possibly still the flywheel being a bit rough?

Any thoughts folks?

[Bugjam1999]

Hi- couple of questions...

I assume the connecting doughnut between the gearbox and propshaft was replaced when the propshaft was changed?

Does it only bang in gear- what about if you shift out of gear into neutral down a hill- does it bang then?

Where in London are you?

Cheers

[Nicholas Lewin]

Hi Bugjam

In reverse order - Teddington, SW London

The banging occurs notably in reverse and at low speed (parking etc). You can get judder changing gear in lower gears - especially if changing down

I don't think that anything was changed two years ago and nor this time. Go back to my timeline above: when I bought the car the transmission was smooth with no problems. The transmission banging has only started since the gearbox was changed (and the gbox was changed because as I now know, it was defective)

I haven't tried the freewheeling in neutral trick - I will try to remember to do that some time. Like I say tho', the banging only occurs at low speeds and once on the move, by and large the transmission is fine...

[Bugjam1999]

I’ve reread your timeline- sounds like something is wrong with the replacement gearbox, since it hasn’t ever worked without noise. Where did you get it from?

M47 gearboxes are so cheap now that if you could swap the gearbox yourself you could replace the gearbox you have with a known good one for little money. Perhaps not so appealing as a test if you’d be having a garage do the work though due to the extra cost of labour...

Are your engine and gearbox mounts in good condition? Propshaft ujs?

Cheers

[Stephen Edwin]

Re the old messed up shaft in the previous gear box, let us not ignore that, just in case. Incidentally in general I'm curious or possibly concerned how that happened.

The replacement gearbox, who fitted it, skimmed the flywheel and refitted the gearbox?

Does the banging sound and feel like something internal to the transmission, or like knocking against the body of the car? I get the impression you are talking about knocking against the car body? Can you get the use of a mechanic's stethoscope and would that help?

If the engine is ticking over, and by laying down on the ground to listen, is there any knocking even a gentle tapping sound? If so can that sound be relieved by say slightly supporting the gearbox on a jack?

Looking also at the timeline, and with experience of a similar problem on a car of a different make, my hunch is engine and/or gearbox mounting[s]. That is even or perhaps especially if the mountings or any of them were replaced recently.

Perhaps replace all the engine and transmission mountings. Using genuine Volvo parts. Try to do it by supporting the entire engine/transmission assembly so the mountings are not under strain during the process. Then, with little or no weight or stressors on the mountings, tighten them up incrementally. Tighten each mounting a little at a time, in turn one by one. If any sort or form of resistance is encountered, try to check it out before continuing. Get the whole situation as stress free for the new mountings as possible. Do it thy self or see it done.

You have mentioned to me a vibration of a different component at or about a particular road speed. It does sound unrelated. But ... I suggest always keep an open mind.


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[Clifford Pope]

What exactly do you mean by banging?
A mechanical, metalic sound from a gearbox, as if something has broken or come loose?
Or a suspension-related sound, as if something is moving about too much on its mountings and causing a thumping noise or vibration?

If it wasn't that you've said all the suspension bushes have been replaced I'd have said worn reaction arm bushes, letting the rear axle tramp excessively in low gear, and bumping the front of the diff against the rubber bump-stop.

Or a very worn rubber prop doughnut, letting the prop whiplash around under low speed torque or oscilate at certain revolutions.