Gear box/transmission rattle - any ideas?

[jameshoward]

Digital photos I can do, digital recordings I can't, not that I'm even sure I could post it.

Problem: I have a strange tinny rattle eminating from my transmission tunnel. It's been there a while. It is most prominent when the car isn't going too fast; I can't seem to hear it when it is going quickly but that may be because it's drowned out by the engine. The gear shifts (it's a 230sl manual) seem ok and the rattle is there whether I ride the clutch or not. It doesn't seem to be there when the car is static.

I am hoping to take the car to France in 2 weeks (about 1400 mile round trip) and I would like to know (1) if anyone knows what I'm talking about and, (2) is this likely to be a show stopper?

It's hard to describe the noise. It's a very rapid rattle and reasonably high pitched. The best description I can come up with is the sort of noise you might get putting a ball bearing in a metal collinder and whirling it around; as it hits the small holes that's the sort of noise. I wonder whether it's a bearing thing, but there is no good mechanic anywhere near me who I could take it to without shelving my trip plans for the car.

A long shot, I know, but any ideas?

James

[Martijn]

James,

Just a suggestion: most modern mobile phones have the possibility to make a voice recording. You can use this option to make a sound recording of your gearbox.
Then you connect your phone to your computer and transfer the file. Probably you first have to install the phone software.
The most common file format is MP3. But if your phone uses another format, you can convert the file to MP3 via this website without installing any software on your pc: http://media-convert.com/convert

Martijn

[jeffc280sl]

James,

Starting at the very front of the transmission there is a pilot bearing that helps to center the transmission and engine drive shafts.  Next there is the throw out bearing which slides forwards and backwards to engage the clutch.  This is followed by the transmission which contains 4 main bearings and some smaller needle bearings.  The front and rear sections of the drive shaft are supported by a bearing and a large rubber donut.

The outside of the pilot bearing spins with the engine.  The inner race spins with the transmission.  Do you experience any noise with the car stopped, engine running and clutch engaged?

The throw out bearing spins up as the clutch is engaged.  Do you hear noise when the clutch is engaged and disengaged?

I had a bearing fail in my transmission.  Everything was fine, no noise that I noticed and then bam the bearing failed and ball bearings and other bearing shields were spread into the transmission.  The noise was worst when the transmission was under load and I knew right away where the problem was located.  Do you hear any noise when the transmission is under load?  Even a light load would cause stress on the bearing and the noise would become more pronounced.

The last bearing in the link is the mid drive shaft bearing.  Noise from this bearing would occur anytime the rear wheels are turning.  Do you hear any noise while coasting at various speeds with the clutch engaged or in neutral?

[waqas]

Loose bolt or washer somewhere?

Have you check your driveshaft flex disc bolts for tightness?

[jameshoward]

Thank you for your replies. Jeff, this is what I was afraid of - asking a question to which I don't understand the answer. It was a stupid question anyway - how do you describe a noise that I don't even understand!

The noise is most pronounced when the car is pulling off, so I guess that would be when the transmission is under the greatest load. However, it sounds so tinny and that it's hard to imagine it could be a bearing. However, the more I think about it the more I think it must be bearing related. I suppose that the process of checking bearings is markedly not simple? I know there are inspection plates in the tunnel; is there anything I can do there to check?

I've been looking foward to taking the car to France on this journey for ages and I'd hate to cancel. Perhaps I'll tempt fate and in the absence of better advice and no way to check, chance it!

My thanks again.

James

Martijn - thanks for the suggestion. It's a good one. Except my phone only makes calls and sends texts. A phone that records is something I don't have. I think!

[ja17]

James,

Check to make sure the aluminum heat shield is tight. It is above the exhaust and mounted to the floor pan.