Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Observation about our howling bevel box.

Just an observation. My bevel box has been howling like a banshee lately even more than it had been. My Ohlins were installed today, which means my rear wheel was removed and when reinstalled everything‘s realigned properly and the belt tightened appropriately. Although the bevel box howl is still there, it has significantly improved. So I would suspect the noise we are experiencing may not be due entirely to the bevel box. Other factors such as the alignment of the rear wheel and belt tension are factors and I would not be surprised if the alignment of the prop shaft with the bevel box is a factor as well.

Anything that affects the mesh of pinion to crown wheel will have a bearing (pun?) on the noise.

I totally agree Richard. Yes, good pun!

I bring attention to this because in other threads the focus has been on trying various types of lubricants to quiet the noise but these other factors should be looked at as well.

I agree that an excessively tensioned drive belt will not help with bevel box noise but the main reason for the noise is the running clearances on the BB gears, particularly when up to running temperature. Quite how much bearing the various possible causes for the variations in clearances have on this seems to be a mystery, with several knowledgeable people and companies trying unsuccessfully to come up with a definitive fix for this problem. I really don't think that a tweak of the belt tension and tracking of the belt and rear wheel is the real answer, although these may all improve things a little.

If someone can come up with a 100% guaranteed fix for a noisy bevel box, then I may be tempted to pay some money for a quiet BB. No one has said they have sorted the problem 100% for sure yet, some claim improvements but not "a fix".

The prop shaft runs pretty straight and therefore the UJ bearings hardly move, brinelling being a consequent problem rather than a problem with out of alignment.

Perhaps that is why MMC installed the Noise Harness for the bevelbox, to give more tolerance for all different alignment problems.

What is the story with the Super 3 - uses the same BB from what I'm told. Does it have the same noise problem as the M3W? I don't think I've seen anything on this but perhaps have missed the thread. Reminded to look again after a long ride Sunday :-)

Its not the same bevel box although looks similar.

My car was a ‘screamer’. I read loads of stuff about what to do and there was a thread about it. I took the bevel box out and gave it to Nova Racing who are just down the road and who build gearboxes for competition bikes. They took it apart and ‘super finished’ the gears and then put it back together and I re fitted it.
It is much quieter than before now. It is noisy around 40mph but that goes. It is now entirely acceptable and if it had been as it is now I would not have bothered doing anything about it.

Their observations were that it was not as crude internally as we were expecting but the bearings used were surprising and of poor quality.. We did the super finishing as step 1 to see how we go. Next would be to replace the bearings and there is no adjustment possible on the gears, they felt that they were too tight and so we might shim them by opening the box up with a gasket.
I want to use the car this summer but in the winter may go back for further improvements.

On putting it back together I have had problems with drivebelt noise under various loads but last night did loads of trial and error adjustments and after a brief test drive I hope that I have found a happy medium but it was up and down from the ramp tweaking the adjusters.
Is there a definitive method.?!