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MG Midget and Sprite Technical - Metal flakes in gearbox oil

Hello.

I drained the oil from my 1971 1275 gearbox and found a surprising amount of metal flakes on top of the drain plug. They're shiny and chrome colored, and attracted to a magnet.

Car has 112k miles. Used to change the gearbox oil every winter when the engine came out, but realized it's been 6k miles and 5 years since the last change (if I can trust my notes).

I'd appreciate any advice about what the chips tell me about what's happening. I'd like to drive the car this year and try to rebuild the gearbox next winter.

The only symptom I can report is an intermittent nasty rattle when decelerating in first or second. It's worse when cold, and then often goes away entirely.

Thank you.





Mark 1275

Not a good sign. If you don't want to take the chance of having something major happening, I have extra gear boxes. Don't know their condition. but you could rebuild the spare and do a swap in one day, keeping your down time to a minimum. Or you could get a rebuilt unit from Quantum Mechanics in Oxford, CT. Very good work, highly recommended. Look them up on the web. You may get a better price during the Vintage Festival at Lime Rock Labor Day Weekend. Tell John I suggested QM.
J Bubela

Thank you for responding.

So it sounds like it's not something to be ignored. Any idea what tends to fail on these? Is 112k an unusually short life?

Wish I'd done the oil change sooner, not just a week before we're supposed to be in the 70s here.

I welcome the idea of undertaking a rebuild. I'll read what I can about what to expect, and maybe I just need to deal with having the car off the road for a few weeks.

I've had good luck at Lime Rock finding parts, but I take your comments to mean it's probably not a good idea to drive it all summer.

QM's website doesn't say much, but I'll call them.

Thank you.
Mark 1275

The weak point on the 1275 box is the layshaft and lay shaft needle roller bearings. The box was originally designed for the 803cc Austin A30 which puts out 37BHP. The midget box whilst upgraded has to take 65BHP so wear is inevitable The Layshaft is hardened but eventually wears along with the bearings. It becomes noisier in the intermediate gears. At 112K miles its done very well and an overhaul with all new bearings will make a big difference.

The little metal flakes probably come from the layshaft and synchromesh
Bob Beaumont

Damage can depend on your driving habits. Holding and putting pressure on the shift lever will wear shift forks(brass). First and reverse will wear when grinding the gears and the layshaft/bearings(steel) are wear points. Low oil (not in your case) also is damaging. I think you got more miles than most. Where are you in Mass? You can drive it as long as it works, how long that is would be a crap shoot. Filings in a close tolerance environment doesn't make for a long life.
J Bubela

I appreciate the replies.

Good to know what typically wears out, and it looks like those parts are available from Moss. I'll research this week what's involved in replacing the layshaft and bearings, and then I imagine you look for wear and damage elsewhere. Are special tools required? I have patience and expect I'd enjoy the process.

I'd say I pretty much baby the car. I rarely push it by accelerating quickly or shifting aggressively. It does happen, but not a lot.

What will failure look like? Will I be stranded somewhere because the gearbox won't shift at all, or will I lose access to one gear? Might be hard to predict, but I wonder what's likely.

I'm in Western Mass, near the midpoint between Springfield and Worcester. It's a great area for backroads. It's been 10 years since an update, but I have a site that shows the car. If this goes as planned, it will be time to add a page:
www.tinyurl.com/7abt5
I don't think it's a contributor, but that little boy in some of the photos was just learning to drive a standard on this car last summer. Another good reason for a rebuild.
Mark 1275

Yes Moss can supply all you need but do check the layshaft has been correctly hardened. Some UK supplied ones have not been correctly treated. At that mileage I suggest you also renew all main bearings and the needle roller bearing on the 3rd motion shaft along of course with a set of gaskets and rear oil seal.

No special tools required if you are not removing the gears from the 3rd motion shaft.

Failure can mean the box getting noisier and noisier but in extreme cases the layshaft jamming and damaging the gears and the casing.
Bob Beaumont

For what it's worth: I will finally be getting my 1972 Midget Mark III out of storage at the end of April (it has been there for more than 3 decades) and my intention is to put in a Datsun 5 speed with the Rivergate kit. That being said I will probably have a Midget gearbox for sale, condition unknown but I am probably not going to be looking for a fortune & might be able to come to reasonable terms with a fellow Spridget owner. I'm located near State College, PA in the geographic center of the state. I'll keep you posted as things develop.
s1

Thank you, s1.

I'm hoping I don't destroy mine, but it's good to know there could be units available.

I guess my timetable will depend on just how noisy it is, but also on my appetite to get started on the project. It might be one of those things where just thinking about it will have me waking up some Saturday morning and deciding it's time to get at it.
Mark 1275

You should also look at the conversion from Gerald's garage in Calif. Good person to deal with. I have his setup yet to be installed.
J Bubela

If your calling QM, ask them abiut there 5 speed ford type 9 kit, its a bit priccey, but its a complete turn key kit.

If you drive your midget much its nice... lower rpm noise on long trips means alot of beifits

Ive got the datsun 5 speed and id never want to go back to the old ribby 4....the 5 speed just makes the car so complete

Prop
1 Paper

I've got the predecessor to the Gerards Garage Datsun conversion. I got it from Paul A. (never could remember Paul's last name). What I like about it is that it uses a standard Datsun clutch so if it goes out you go to your local parts store and get one as opposed to the Rivergate mix and match set up. Not that theirs is bad, it was personal preference. With the Gerards Garage version you do have to get the flywheel drilled to accept the Datsun clutch but aside from that its a pretty easy switch. The hard part is find the gearbox.
Martin

This thread was discussed between 11/04/2017 and 12/04/2017

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