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MG Midget and Sprite Technical - DIFF CHANGE?

My wife's 1966 Mk2 midget has got a whine when driving, is this due to the diff??
Thinking of changing it anyway so what would be a better upgrade?
Been looking and some have 4.2 - 3.9 etc etc???

Could the whine (wife is not with me when I'm driving it so it's not her), be the clutch release bearing?

Need help as you can tell not really mechanically minded!!!

If it's clutch-related it will vary in pitch with engine revs through the gears, whereas if it's diff-related it will vary in pitch with road speed, that should help diagnosis. A '66 car should have a 4.2 diff and a 1098 engine. Unless the engine is as good as new and preferably performance-tuned then it will struggle to pull a 3.9 diff, it will drive more like a Morris Minor.
David Smith

are you sure it's not a gearbox whine?

I'd look at doing a thorough oil change on the diff (and g/box) and see if that helps any plus you can then see the quality (or not) of the existing oil and if there are any metal bits in there

for both g/box and diff get the existing oil as warm as possible before draining and leave the existing oil to drain for as long as possible to get as much existing oil and muck out as possible

my car had a diff whine and I got rid of it by regularly changing the diff oil and then using a very good quality diff oil
Nigel Atkins

Very good point Nigel, it could be the 'box. Somebody might have put the wrong oil in it ;-)
David Smith

Thanks for your help, there is a slight noise from the clutch when not in gear and the tone does change when you press and release the clutch pedal, you can tell there is a difference and the engine tick over does ever so slightly change. I think this may be the clutch release bearing, if I remember it goes quieter when the clutch pedal is pressed down??
The whine from the back/underneath is a constant noise when moving and does seem to go higher with speed.
I will take your advice and give it a thorough flush out and oil change and hopefully this will resolve the problem?
Any recommendations or experience of a good quality oil to use please????

good one, made me smile :)

but very hurtful :(
Nigel Atkins

you want to do thorough oil changes (whether engine, g/box, diff) which is to get the existing oil as hot as possible before draining and then leave it to drain for as long as possible to get as much of the existing oil and crud out

check the oil drained for metal bits, gunge and crud

if there a lot of metal bits you might need further advice

if there's a lot of gunge and/or crud or the oil is a water like consistency you might want to consider flush cleaning the diff

I can 100% recommend the oil that took away the diff whine on my Midget, that had been reducing from previous regular oil changes,

- its Mobilube 1 SHC 75W-90

you may be able to get it from an Esso garage but I don't know as I can't remember the last I even saw an Esso petrol station despite their TV adverts

or you can get it on-line, just one example (check for postage discounts) -
Nigel Atkins

I like lucas 75-90 gear oil

For clean out ive heard that K1, kerosene, or what you guys in the UK call parafine works really well ... just drain the old, pour in the K1, drive it slowly (5-10mph) for a mile or 2 ...then drain and fill with fresh lube

Prop and the Blackhole Midget

Diff whine is generally due to mis- alignment of the pinion to the ring gear. If it whines under acceleration vs. deceleration the pinion is either too close or to far away....can't remember which is which. They normally blue the teeth to ensure proper contact. My old GMC truck had shines to adjust this, don't know whether midget/sprite has shims to facilitate such adjustment.
Kth Hurt

This thread was discussed between 25/09/2014 and 03/10/2014

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