vibes

[les]

Could do with some opinions please, at about 35 mph I get some vibration/rumble, if I change down to 3rd keeping the same road speed it goes, which spoils my theory of prop shaft balance as this is revolving at the same rate if the road speed is the same. Would you agree?

[bigginger]

Surely you have to increase engine/prop revs to maintain the same road speed in a lower gear?

[Pyoor_Kate]

Nope, if you think about it the engine speed changes but the prop will continue to rotate at the same speed ('cos the gearing on the diff doesn't change - it's only the gearing at the gearbox that changes).

So you're half right

[bigginger]

Aha - ish. I'll ponder that Think I've got it...

[Willie]

The prop would have to be wildly out of balance to give symptoms at that low
speed I think. The only thing which changes in your description is that the
engine revs higher in third to maintain the same speed . Do the
symptoms alter if you increase speed? If it was the prop it would get steadily
worse as you speed up.

[Cam]

Les, it sounds like it's more rev related than speed so it might well be that your clutch cover is out of balance (badly)? Has it just started doing it since you changed the clutch?

Does the vibration occur when revving from stationary?

[bmcecosse]

What happens at higher speed- say 2x35 = 70 mph ? Maybe just going through a vibration period - does sound like it's engine related, but at 35 mph the engine is hardly turning over at all ! Sure it's not worn suspension/buckled wheel/damaged tyre (lump on tread or sidewall)?

[les]

Thanks for the response, travelling at about 30 in top vibration sets in, reach 35 and it goes and doesn't come back. This has happened since gearbox and clutch replaced, so you may be right Cam, although it seemed to locate nicely. Not tried reving stationary, but will do. I am also going to check engine steady.

[bmcecosse]

Is the wire rope restraint maybe too tight ? Was the little oilite bush in the flywheel centre hole ok ?

[les]

Wire restraint is just taking slight tension. I renewed the oilite bush which went in squarely. I'm now thinking of the gearbox mountings, but I am possibly making more of this than I should, although I can't recall this before doing work on it.

[bmcecosse]

Slacken the wire off slightly - it's only there to stop the engine bashing the radiator in a hard stop!

[Cam]

Well, It's an engine steady cable really and helps eliminate judder. The engine and gearbox mountings will hold your engine in place and won't allow sufficient movement to hit the radiator even in an emergency stop. I have run without a steady cable for ages with no hitting problems (still do on my modified car as there is nowhere to mount it!).

[bmcecosse]

Aye - but if it's too tight it may be causing these symptoms. I think it's best to have it there though !

[Cam]

Yes, it is best to have it there. Sounds like it's adjusted correctly though as Les says in his earlier post.

[Willie]

I don't agree with that CAM, the steady cable is to stop the engine lurching
forwards under extreme conditions. On the Minor it has the added advantage
of stopping stress on the clutch operating mechanism which,uniquely I think,
is suspended on one side on the chassis rail and on the gearbox on the other.
The engine mounts are quite capable of ripping off under stress and,when I
left off the same steady cable on an early MGB with the same sort of set-up
I found that the car would jump out of third gear going down hill because the
engine mounts allowed the engine to move forward enough to hit the gear
lever on to the floor and knock it into neutral.

[KirstMin]

Well I always thought it was there for the reason CAM states - to stop judder. Which is why you notice it much more in reverse when you dont have one. I can't see why it would be called an engine steady cable otherwise and I dont see how the engine is going to fly through the radiator in an emergency without one in place.

[Cam]

I don't agree with that CAM, the steady cable is to stop the engine lurching forwards under extreme conditions.

Yes, I know you don't agree, Willie! We have had this discussion many times before have we not?

But the point is that your engine won't hit the rad in an emergency stop without one (all other mounts being in good order) and judder is more prevalent if you don't have one!

It sounds like the engine/gearbox mounts on your MG were a bit knackered if they were allowing THAT much engine movement. Of course fitting a cable which holds the gearbox back would eleminate the problem but I don't think that was the reason that they were fitted. We need a Cowley chap to answer the question fully!

[Packedup]

Not a Minor, but I've lunched a rad by having the metal engine fan go through it, without the mounts tearing or seeming otherwise worn out. It's amazing how much give and stretch the rubber can have under extreme loads!

[Cam]

under extreme loads!

That's it isn't it?

I mean the Series MM and early series 2's never had the cable OR a top engine steady...

[Onne]

Maybe because there is not a lot of power? But you are true, my MM doesn't have one