Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Final drive belt jumping survey

+1 on the NVH bracket playing a part in the knocking sounds. I reckon that it may be bouncing up and down under certain circumstances and hitting the chassis (or something else).

My BB (2014) is pretty quiet regarding whine from what I read on TM. But on the other hand it is very prone to 'backlash clunking' unless I am very careful in the gear changes.

I just wonder whether it all depends on how the BB has been set up - more gear mesh clearance = more clunking but less whine and vice versa.

Do others suffer one fault to the exclusion of the other or possibly both?

Whoa - Had the gunshot tonight on my way back from a local car meet. Fortunately I had read this thread so (after a few seconds of panic ) was able to attribute it to belt slip.

I think I'll be tempted to tweak up the belt tension a tad as it's not a nice noise!

I still find it odd that it's the belt that is jumping. It's not as if it's easy for a toothed belt like that to somehow launch out of the sprockets - even when quite slack! I suspect it is a function of wheel slippage and lash in the belt's tension path when that occurs. I reckon we should compare tyre type with slippage gunshots and see if a more progressive tyre tread reduces the effect?

[Notwithstanding that Phil still gets the bangs even after converting to a chain drive! Therefore there could easily be something else at work...]

My data:
tyre = Yokohama and slippage = lots

Whoa indeed Bunny, read my site www.bleazey.co.uk - it is not the belt jumping!

Do,have a good read of Phils web site.

It makes very very interesting reading indeed.

Quite an engineer Phil still is unable to fix the banging noise from the Bevel box.

I suffered this quite alarming noise from my BB and was very concerned that the gear mesh inside would break up ..with potentially disastrous consequences if it locked up.

I think there was a lock up in the USA from memory caused by this happening. Not sure of the outcome but nobody got hurt as the car was travelling in a straight line.

For my money it's caused by the helical gear inside the BB becoming loose/ breaking down.

But I am not an engineer!

It sounds like there are a few mechanisms for tooth jumping, and maybe not a single solution for all cases. However, we can certainly generate it on our car with belt tension alone.

I have videoed the prop shaft under load and it moves very little even with the rubber mounting kit on the bevel box. I thought maybe it would twist and give some slack to the final drive but it seems not. The search continues!

I was all set to do that at the weekend , but well done that man !
Did you manage to video it when a 'clonk' happened ?

Sadly, it wouldn't clonk while being filmed! It's probably female!