Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Bevel Box Oil Mystery

You fill by the second hole
The orange is not for the level
Just for air

The factory filled to the orange plug on mine last service as I checked it when I got it home.

It is amazing that everyone is so confused about something so important. Says something about Morgan and its people to leave the very people who keep them in business in the dark.

I changed oil Two Times And i Never touch orange cap.

So perhaps there's a compromise position somewhere - above the generally accepted upper fill hole, but slightly below the orange 'breather'? The only risk I can see is over-pressure blowing out a seal, unless the Orange Cap really is a proper breather, in which case the risk is oil coming out and potentially getting onto the back tyre.

But if filling to the Orange Cap makes the BB run quiet, then I'd be tempted to run the breather (if indeed that's what it is) into a hose and secure it somewhere other than directly in front of the rear tyre. That way it would be safe. I definitely need to try filling my BB higher and see for myself the results.

I thought there was an overfill outlet??

If so the oil would fill to there and no further?

good idea about the overfill hose - or together with a catch tank of some sort...u know a simple plastic bottle ...like a classic bike or older race car.

Mine has done 2500 miles with oil up to the orange cap with no discharge and is still relatively quiet as it always has been.

The orange cap is labeled "oil"...it is difficult, if not impossible, to believe that oil is not supposed to be inserted into said hole - though these are Morgan's we're talking about.

I suspect the right answer is to fill via the orange cap, but only to the level of the hole above the drain hole...

For my next flush, I'll be removing both the drain bolt and the bolt above it., I'll then replace the drain bolt and fill via the orange cap until oil leaks out the hole above the drain hole. I'll then replace all bolts and drive. If the car is still quiet, I'll leave things as they are, but if the rattle returns, I will then fill to the orange cap.

As an aside, the orange cap looks like a proper plug - not a breather, it has a washer...

Over filling a unit such as this will not harm it, other than possibly spitting oil out the vent.

But what it does is rob hp from your driveline.

You're floating all the parts in the BB in oil and not light oil at that. There is a LOT of drag and you only need "enough" oil to keep the parts lubed and cooled.

Why do you think motor builders use windage trays under the crank, to keep the oil from the pan getting on the crank throws and costing precious power.

When we ship gearboxes out on our equipment, they're filled to the manufacturer's specs and usually there is a "fill level" hole about 1/3 the way up the case. This amount of oil is more than sufficient to lube and even our gearboxes get hot enough that they are hot to the touch.

Again, if the BB quiets down with over filling them and they don't puke out the oil, you're probably not going to notice any lost hp with your seat of the pants dyno.

Good luck to all on the BB lube issues.

Have a great weekend to all!!!

As we know the bevel boxes are made by Quaife who have a very good name for all types of gearboxes and differentials. I can only think that our bevel boxes are made down to a price and not to the same degree of accuracy as other Quaife products.
Given the price of our 3 wheelers it would have been in Morgan's interest to insist that Quaife solve the noise problem.
The introduction of the NVH kit appeared to do very little in terms of reducing the noise and in any case it was only an attempt to mask the symptoms rather than cure the original problem.