Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Backlash

I've long suspected that there is a significant amount of backlash in the bevel box. Of course you need some or it would seize. However had the boot liner out yesterday and when leaning on the tyre noticed that if I rocked the old girl backwards and forward in neutral I got a distinct clunk form the bevel box area.
I would be interested if anyone else gets the same. You don't need the boot liner out to do it.

One sets up the old fashioned bevel boxes with very little backlash. I had to rebuild mine after I lunched the input shaft and I could find nothing written. So I made sure the thing could go all the way around (four turns of input shaft on an old one) didn't bind and had a teeny tiny bit of extra movement to allow for heat expansion.

Then got it examined by an experienced three wheeler owner who was happy with my efforts so put back and car driven!

In your case though, the 'backlash' you are seeing could come from further forward, but the sound is coming from the box if you get my drift.

Thanks Martyn
I'm sure your right. Could be anywhere from the gearbox back!!!
Probably fine but the old 5 speeder hypochondria can kick in really easily.

I have noticed the same noise but it does not seem to be accompanied by any appreciable backlash. I asked MMC to take a look at this point when it went back for first service. They examined it (thoroughly I think because it took a couple of hours extra) and said everything was normal. That sort of made me happier.

Thanks good feedback
I think its accumulated slack in the drivetrain. Definitely a very mechanical clunk.

Well, if it helps, mine has only done a few hundred smiles and it seems to be the same as your description. Trouble is, ownership comes with certain amount of disaster anticipation. The scale of the anticipated disaster is directly proportional to how many posts you read and how you interpret them
How would you interpret 'I only get 3000mls from my rear tyre also my bevel box is shot' ?
Anyway, my car similar, don't worry too much

All transmissions have free movement: if you rock and bike or car in the same way there is noise.
On a car there are normally "metalastik" joints that take up the free movement somewhere in the transmission, like this:

Rotaflex

This is from a Triumph Herlad and the rotaflex coupling sits between the differential and the wheel, adsorbing lash between wheel and transmission.

On a bike the cush drive in the rear hub will do the same thing, but without anything that is designed to adsorb the lash between wheel and differential (bevel box)it is adsorbed by the belt and transmitted to the bevel box.

The M3W Centa drive has the same effect adsorbing load changes between engine and transmission, but it isn't enough. Something is needed between wheel and belt. A cush drive.

End of Rant.

Thanks Grockle
I was worried it had more to do with a bad stall due to a very bad heal and toe attempt.
I do get the small clunk when accelerating gently and changing up, hard acceleration not a problem as all the slack is taken up by inertia of all the drive train components I think.

I'm just suffering 3W hypochondria. Must be the fact I now have 15 k on the clock and nothing's gone wrong for over 6000 mls. Still love the old girl and can't wait to take her out tomoz.

All it needs is a nice Roto-Flex coupling in the drive train, just like in the Lotus Elan....oh! wait a minute...

I'll be contrarian on the cush drive issue, I don't think that additional in-line damping will achieve anything very much. I think that the real problem is that the S&S X-Wedge is a styled engine rather than a thoroughly engineered engine. To illustrate this ask yourself how many other engine manufacturers boast about how heavy they have made the crankshaft? To me the engine is a strange mix of lots of low-down torque that you mustn't use because it will tear itself (and the drive line) apart and no top end because it is too heavy to rev so you actually end up with a motor that has a really rather narrow useable power band.
Having said that, it does look the part, it sounds the part and I think that if as others have suggested you match revs on the way down the gears then you don't have the massive inertial loads going through the drive line trying to spin that massive crankshaft up in an instant when the clutch is dumped. Without those loads the bevel box and the sprockets will have an easier time. At the risk of tempting fate I will add that at 15500 miles I am on the original bevel box which was supplied with the infamous black goo additive (flushed out within 2 weeks of delivery) and the rear sprocket has done all but the first 1100 miles when it was fitted at the instruction of the factory for some unspecified but "known" fault. The sprocket is also one of the early ones that has the belt hanging off to the side - which is another piece of engineering genius; a narrower belt would probably be more fit for purpose! Maybe these things have lasted (so far) because I drive so gently...
The car is enormous fun but does need to be driven around some of its quirks. It certainly is not the thoroughly modern but 1930s styling car that many expected but lies in some strange grey area in between that also plays host to many large idiot grins on the faces of the drivers, passengers, bystanders and from time to time, breakdown truck drivers.

From what I've gathered on Talkmorgan and from Peter's book, RedThree's statement could be applied to the entire vehicle, not just the engine.