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MG Midget and Sprite Technical - Sticky second gear.

Oddly enough the change in my gearbox is easier when cold. When it warms up it tends to hang in second gear and needs a very positive movement to come out of second and change into third. All other gears are OK and I can ,in fact drive around the problem but it just seems a bit strange.
Roger D

Mine does that a bit, it’s awkward because you need to push it so hard that sometimes it ends up almost hitting first gear. It’s a newly rebuilt box as well. Not too much of an issue, just slightly annoying.
John Payne

John, That describes my problem exactly.
Roger D

Just a guess but it sounds like the gear is over engaging meaning that the slider is going past where it should stop and the detent balls are starting to come out of their respective holes. I had that happen once with first gear. It got stuck and I had to pull the box out to fix the problem. I don't remember how I did it since this was over 50 years ago. And since I now have the Datsun box, I don't worry about it leaving me other things to worry about.
Martin

It is possible for first gear to overthrow, but not second.

I had the same problem on my first midget, some 40 years ago.
Dave O'Neill 2

Dave,

Now that I think about it, you're correct. Forget what I wrote earlier.
Martin

I agree its usually the 1st gear overthrow that is the problem. If I recall the selector rods have detent balls which are tensioned by springs. The springs and balls are located under the side cover of the gearbox. It may be that ball (s) are jamming slightly when the box heats up or the wrong springs have been fitted.
Perhaps a gearbox oil change may help?
Bob Beaumont

As Bob has already put it I'll second a hot long drain of the existing oil and refill with a high quality oil that copes better with higher (and lower) temperatures might help. Probably wont cure the problem but could ease it leading to less wear on vehicle and driver.

You can use gear oil in the gearbox even BL said so see attached TSB. Owners of T-series and MGA cars with gearboxes from the 1950s often go with Red Line MT 90 (the T-series and MGA drivers seem to be more progressive than MGB or Spridget owners).

MT-90 75W90 GL-4 GEAR OIL
. Safe for brass synchros, as it lacks the reactive sulfurs found in some GL-5 oils that cause damage
. Eliminates common hard shifting problems in manual transmissions
. High performance gear protection and longer synchro life
. Extends the life of gearbox synchronizers by reducing wear caused by friction
. Recommended for GL-1, GL-3 and GL-4 applications, as well as where most special synchromesh fluids are specified.



Nigel Atkins

I don't think you can run 75W/90 in an A series box. it should be normal 20/50 engine oil.
Bob Beaumont

Why not it's not that different to a MGB that also runs with 20W-50 engine oil but has to change the oil every 2 years or 24k-miles.

The boxes of earlier cars such as the MGA had engine oil (SAE 30 which went on to become multi-grade 20W-50) yet MGA drivers successfully use Red Line MTL (75W80 GL4, SAE 30, 10W30 and 5W30) or Red Line MT 90 (75W90, 80W90, 90 and motor oil viscosities of SAE 40, 10W40 and 15W40). Bearing in mind these numbers refer to bands, one oil at 40 could be nearer 50 than another 40 band oil.

I'd happily run a modern formula GL5 that is safe with 'yellow metals', in fact I do. One time people were told the the sun goes around the earth, some believe the Earth is flat (perhaps it is?) and then there are oil beliefs, as always each to their own.

As I've put (many times before) I was told in the 90s that using Mobil 1 in my "classics" (overpriced and overvalued old cars) engines would ruin them, this often by those whose "classic" wouldn't do in a decade or more the annual mileage of one of my "classics". I put tens of thousands of miles on those engines and so did the following owners as they didn't get ruined.

Leyland LT77 gearbox three different types of oil were recommended for it at different times, ATF, gear oil and engine oil engineers aren't infallible and things change and progress or after 50 years of use and abuse, perhaps new parts with worn parts a bit of experimenting might be required to find what's best for the particular gearbox.

The engine oil you put in the gearbox today isn't the same as when the cars were new even if it still has the same name, Castrol XL, Duckhams Q (which is Comma anyway), it is a different updated formula, so progressed, if you want to you can progress further perhaps with a modern gear oil.

But, each to their own.



Nigel Atkins

Yes, I think I will try a different oil next change. Currently using Millers 20/50 for Minis. The idea being that it is the correct grade and also formulated for gearboxes as in the Mini. Probably a load of old snake oil sellers guff though!!
John Payne

John,
it shouldn't be, ring Millers up and ask them, I've found them very straight forward in my dealings.

IIRC it was the Mini that hastened the acceptance (and need in its case) of 20w50 oil, or I might have remembered wrong, dreamt it or on fantasy island. I'd always have to refer to information sheets, keep a library of information instead of having to remember it all but now I'd not remember the library index or system or where the library is stored or located.

Now was I going upstairs or down, doh, I'm in a bungalow.

Nigel Atkins

I think one of the issues with the Spridget gearbox is the size of the oilways in the layshaft.
Dave O'Neill 2

All the more reason to have a good quality oil that remains free flowing through a wide range of conditions and remains so for longer - whatever your choice of oil and type. And to have cleaner oil, without any bits in it.

The idea that any oil is fine so go for the cheapest never appeals to me as that maybe that it ought to be the case but often it isn't even from when the boxes are new let alone decades of use and abuse later and more so when they've been rebuilt with new parts mixing with old.

I also can't follow the idea that there's not a need for interval (time or mileage) changes of the oil, some say the gearboxes are sealed so no muck but the oil never looked clean as new when I've done gearbox oil changes and Red Line show in their leaflets that their oil and others have viscosity loss after 5,000 miles.

I've also found service interval changes of the rear axle oil to be helpful.
Nigel Atkins

This thread was discussed between 15/07/2022 and 18/07/2022

MG Midget and Sprite Technical index

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