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MG Midget and Sprite Technical - gear box noise

my 71 midget gear box makes a lot of noise in 1st and reverse. I have motor oil in the gear box. Any recommendations on this.. like a gear oil to use
Ken Bargeron

It depends on what you mean by noisy.
Most Midget/Sprite gearboxes are noisy in first and reverse.
Much noiser than 2nd ,3rd and 4rth anyway.
G Lazarus

well I should say loud winning noise. Should not be normal.
Ken Bargeron

That sounds normal for an A series box.
Has it just started making that noise or has it always been like that.
Someone will be along soon to tell you what gearbox oil to use (I have a 5 speed so I use semi synthetic) and whether I've got my previous answer wrong or not.
G Lazarus

Use 20/50 engine oil...
Anthony Cutler

the A series ribcase box was designed to use 20/50 engine oil as it is essentially the same internals as the classic Mini which of course had it's box in the sump.
David Smith

Ken,

An important thing to remember about midget/sprite boxes is that they still refer back to an era when first gear (like reverse) wasn't really intended for hard and regular use. The logic behind the pre-war style of driving is that first gear is really only intended the get the car moving, or to climb a severe incline, while the real work of acceleration is done by gears 2/3/4. For this reason first and reverse gears are built quite weakly, with straight-cut gears and no synchro, as nothing more would usually be required. For me, this is part of the charm of using and driving an original Spridget.

These days, of course, folk are used to using every gear, sometimes hard, and this lead to wear which gives rise to the noise you have. If you dismantled the box, you would probably find that the layshaft has worn (an easy part to find) and probably the needle bearings on which it runs, which means that the mesh of the gears will have altered. Mind you, gearboxes can and will soldier on for years like this, so I shouldn't bother too much unless you were going to get the box out anyway.

By the way, I used to be a tuba player, and followed closely the activities of other practitioners. Your name is unusual, and I am wondering if you have a relative by the name of Ken, who I used to see on recording personnel lists sometimes?

G
Gus Gander

it's always been my understanding that straight cut gears are actually stronger than the same size helical cut, which is why strright cut gearsets are made racing. Helical was developed *because* it runs quieter, straight cut is noisy by its very nature, granted it may get a little worse with wear but not significantly so.
David Smith

Ken

Sorry about the last enquiry about any possible relative of yours. The name I'm remembering is not Ken, but Dave Bargeron.

As for straight-cut gears, they are, as Dave Smith says, generally stronger than helicals, but they will be weak in a midget box not becuase of the type of gears they are, but because they weren't built strong enough for modern-style driving. I suspect they were straight because 1st gear (and reverse)wouldn't be used much in old-style gearbox use, so would cost less, and, as a parallel, the noise wouldn't matter either.

G
Gus Gander

Gus,
No problem about the inquire on the name. Funny thing is I am a guitar player and have played with a lot of folks non-professional in and around Atlanta Ga.

About the tran noise. I was just really wondering if another fluid like synth oil might help.

Thanks of all the replies

BTW picture of my car uploaded..


Ken Bargeron

Hi Ken I have a 73 midget with an original box and it has always been noisy in first and reverse, I think its the nature of the beast!
p sewell

Hi Ken, I have always used 20w50. I have heard you can use some gear oils but never seen it recommended by anyone that owns spridgets. I have read that the synth gear oils can be too slippery for the syncros to function properly. I'd leave it enough alone unless you are having gears pop out, maybe inspect at the next engine out job.
CJCharvet

There's noisy an there's NOISY....!

Granted first and reverse, by the nature of their design will be noisy as pointed out above, they are straight cut.

Sadly, the first gear really does suffer badly on tired Spridget boxes and if you were to strip yours, I guess you will find wear on the lay shaft bearing surfaces and also on the lay gear bearing surfaces, plus worn teeth on the first gear and corresponding lay gear.

I have rebuilt enough of these boxes to know that when one comes along for rebuild as being noisy, it will always go out with a new first gear, new lay gear and new lay shaft plus all other bearings plus possibly new synchros etc.

Sadly, these boxes are not cheap to repair properly....

Mark.
Mark T. Boldry

This thread was discussed between 23/01/2009 and 03/02/2009

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.