Hi.

I have this noise coming from the transmission in first, second and third gear. There is nothing in fourth gear.
Transmission is in perfect shape and changes with the most lovely mechanical click. Requires no force to change through the gears and the movement is smooth as can be.
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A person on Benzworld suggested it was the bearings in the lower shaft causing it, as they control first, second and third but not fourth. However I thought any form of bearing noise would really rather quickly become worse as the car was driven. This has always been the same, the noise never gets louder and there's no grinding or anything. It's just that noise until fourth that changes to the RPM of the engine.

I initially thought it was the synchromeshes inside the transmission howling a bit like in most old cars, I still believe this because of the above reasons.

Could it be the bearings as suggested or could it be the synchromeshes? Also wondering if I should get this looked at or just drive it, considering there has been no change at all since I bought the car 1½ years ago and the fact that the transmission shifts perfectly fine.

EDIT: The transmission was rebuilt 12-14 years ago and has done less than 8000 km since. It's why I also do not suspect the bearings of wear.

Thanks!

Jackpody:

A few words of identification of the model year and the engine type will help; that said, your description of the noise suggests to me that either,

1) there is unusual wear of the input shaft gear and the mating countershaft gear, OR

2) at the time the transmission was rebuilt the input shaft or the countershaft was replaced with one the gears of which are not a good match with the other.

Oh I totally forgot. Let me summarize:
W108 from 1970. It's a 280 SE with four on the floor (pretty rare these days for a 280 SE with a 4 speed manual on the floor!). Has the M130.980 Mercedes inline six with fuel injection and converted to electronic ignition.

To 1)
Would unusual wear reproduce the sound of straight cut gears (albeit a lower tone)?. I only thought whines came from bad gears (more of a grind) or from bad bearings.

To 2)
I've only own the vehicle for the past 1½ years or so. I'm not quite sure if it has always made this whine.

I think I'll go with a transmission oil change in the start of the season to see if it goes away. I have no service records of the oil being changed ever since it was rebuilt 12 years ago.