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MG Midget and Sprite Technical - Very weird type-9 issue

OK, so continuing in my Type-9 issues vein, another problem (not really a massive problem TBH) hat I had when I ran it before was that the car would creep forward, very slightly, when stationary and in neutral (with the engine running). No clutch smell and flat surface. Can't remember whether temperature affected it.

Various potential reasons suggested - input shaft not shortened enough, clutch not disengaging properly etc. BUT the box is in neutral...

Best one I heard was gearbox oil causing some sort of wind up in the box and creating drive - any other thoughts? Would the fact it was fresh oil mean this might lessen over time?

I'm definitely going to try the Castrol Syntrans oil this time, even though I've got 2 litres of Comma GL4 in the cellar - see if that stops it.

Still, quite weird?
L McInally

Yup definitely the wrong ( too thick) oil could cause that. When I drained the original ford oil from my T9 box, I thought it had the consistency of water.
Lawrence Slater

Lloyd,
I've no idea if oil might be the cause unless it's old or very old

on engine oils if the oil is very old and has been standing undisturbed for a number of years it needs a good shake up to make sure the various added packages of additives haven't separated

well actually the oil needs recycling and not put in your engine but I know many would sooner put in what they have immediately available rather than buy replacement, after all it's only oil, they're all the same, been in the ground millions of years, etc.

I don't know if this is the same for gear oils or to what extent but I'd have thought so

if the Comma is SX 75-90 semi-synthetic and it's not too old (probably a fill date on bottle, if there isn't a fill date then it might well be too old) I'd use it as a short or medium term flushing oil

do a thorough flush of the existing oil now, get the existing oil as warm as possible and leave to drain for as long as possible to get as much of the existing oil and muck out as possible

and refill with Comma if it's usuable

I'd at some later stage do another thorough oil drain and refill with the Castrol and let us know if there's no noticeable difference in gear changes with the different oils

I'd also check to see if you need to fill to bottom of filler hole or 20-25mm below that
Nigel Atkins

I remember many years ago, probably my first Mini Van (NUB882F where are you?) and the exhaust was blowing somewhere. I put it up on axle stands and started the engine so I could have a look underneath (an age of innocence?). Walked around to the front and noticed the wheels going round. Thought I had left it in gear but when I checked it was in neutral and yet the wheels were turning. Thought it was just peculiar to mini's but obviously not.

Rob
Rob aka MG Moneypit

Not sure if pertinent but my neighbour recently had the type 9 in his Morgan rebuilt as the engine was out being rebuilt and the gearbox used to jump out of reverse, his wife as passenger had the duty to hold it in reverse to prevent the jumping out. The guy that rebuilt it said the box was on the point of failure and he hadn't seen worse, 5th gear specifically, although reverse was shot. I didn't see the parts but apparently a 5th gear bearing was blued due to the state it was in so may have been dragging. The gearbox seemed to work OK apart from jumping out of reverse and noisy in 5th.
David Billington

Hi all when I fitted my T9 I took Nigel,s advise and filled it with Castrol Syntrans all works fine no forward movement at traffic lights etc than I do use the hand brake
C Walsh

I would expect this to be perfectly normal in a light car on level ground.

The input shaft in the gearbox will be spinning at around 1000 rpm. So any oil, however thin will be stirred up quite vigorously and will be rotating inside the box at much the same speed. Ever used a paint stirrer on an electric drill? Or one of those little battery powered things for frothing up your coffee?
Once the fluid (oil) is spinning inside the box it will have an effect on the other gears, whether in neutral or not makes no difference. And if the car is light enough, has free moving transmission and on level ground it will creep forward.

Try putting the handbrake on when you stop.
Guy Weller

Very interesting chaps - thanks. Nice to know it isn't necessarily a sign of trouble.

I got a couple of litres of the Castrol from Halfords today and will be putting that in methinks.
L McInally

Lloyd,
let us know if you notice any difference with using the Castrol (should be immediate) and if not please moan at me

I found an immediate difference but that was on the assumption that Comma SX75-90 semi-synthetic was originally in the box and judging by everything else that the 'specialist experts' done I might be wrong and it was a non-recommended oil they used or was left in the box when they bought it
Nigel Atkins

I've just put the Castrol Syntrans in my MX5 six speed gearbox and it has mostly cured the slight notchyness these boxes suffer from into 2nd when cold. Strangely it took quite a few days/miles to make any difference, can't explain that one but I was told that would be the case.

I'll be putting it in my type 9 next time I change it.
john payne

I wish when I had my box rebuilt I had asked them to put a drain plug in.

Whilst box is empty (but now in the car) I wonder whether I could very carefully drill a hole and tap it 1/8 NPT/M10 or whatever from underneath. Partially fill with oil or maybe paraffin(?) and drain to remove swarf, tap hole and repeat. Fit plug/bolt and copper washer, then refill with chosen (Castrol) oil and use.

If I don't like it then much easier to swap oils.

Silly idea?
L McInally

There's a flat spot on the bottom of the CI part of the casing that looks as if it is designed especially for a drain plug. Its where I fitted mine, but not when it was in the car. The problem is that there is a large circular magnet sitting inside the box at this point and it would pick up a lot of the swarf which wouldn't then come away cleanly when the box is drained and flushed.

The other place for a drain is in he bottom of the alloy spacer section immediately behind the CI part of the box. I think that is where Arie has his drain plug fitted.
Guy Weller

I'd say it's doable in the car. Since you'll be drilling up, the swarf will be withdrawn down via the sprial of the drill and gravity. Drill slowly, and use something like tallow, on the drill bit and tap, and pretty much all that doesn't fall down, will stick to the tallow. As guy says, there's a magnet in there to collect loose metal from the gears, so I reckon it'll also collect and hold any metal that doesn't stick to the tallow.

I did mine out of the car with the box upside down, but very little swarf if any, ended up in the box.

Lawrence Slater

Lloyd,
a photo of Arie's g/box (I wish mine looked a quarter as good) with drain plug


Nigel Atkins

John,
my first thought would be that there was residual of the previous oil in your Mazda g/box that needed washing around but that is totally disproven by my oil change as I had to syphon out the existing oil and know there was plenty left in there yet I had a noticeable immediate improvement, not kiss the ground in joy level of improvement but certainly noticeable

I've done a couple more syphoning and refills to possibly dilute the previous oil but no more gains just more of the good stuff in the g/box I hope
Nigel Atkins

Too late for me at this point - all fluids in and engine fired up this afternoon. I'll see how the Castrol goes - could only get about a litre in. Need to set the clutch up and then bed piston rings in before I can get a feel for how the Castrol behaves.

Interestingly - mate helping me is a transmission engineer developing boxes for various supercars - Lamborghini and Audi R8 thingys. Says they supply box for the Audi that takes 600ml of fluid. Customers panic when they can only drain out/refill 450ml - they have to tell them that that's exactly as it should be - the 150ml just sticks to the internals, as it should, so unless you've got a complete dry rebuild you'll never get all the fluid out, or in - unless you flush I suppose.
L McInally

same when you drain the engine, diff and coolant, dry capacities are nothing like drain and refill capacities

last time I syphoned and refill my g/box I got about a litre back in, it might have been a little more but I can't remember now

I like to get the existing oil hot so that I can get it through the very narrow syphon pipe I have to use and one time I could smell vapours coming up and saw a whiff of vapour leave the fill hole, despite my syphoning being very slow it would seem the gearbox gets very hot and takes a while to cool especially when you remove the oil from it
Nigel Atkins

This thread was discussed between 31/07/2014 and 03/08/2014

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