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MG Midget and Sprite Technical - Diff whine, possible cure?

When I replaced the pinion seal on my diff, I made the mistake of not marking the pinion nut with the flange and I retightened it back up to 140 lbft thereby crushing the spacer more and pushing the pinion further into mesh with the crown wheel. After a few thousand miles it has now started to whine.
The diff has a newish cross pin and the sun and planet wheels have no play in them.
I have been thinking, should I take a chance on buying a new collapsible spacer and pinion seal and tighten the nut to original 140lbft in the hope that it will cure the whining, or am I wasting my time?

Bernie.
b higginson

You know the old 'cure' I presume? Not that I would recommend it!
GuyW

Hi Bernie
I have sent you an email re using a solid spacer and benefits thereof together with external shimming of carrier bearings to set backlash.
S G KEIL

Bernie
I didn't mark my nut position either but just snuck it back up to give an acceptable reading on a spring balance. There's a bit of whine but I thought "they all do a bit". There's a long thread about this in the archive.
Bill Bretherton

Guy, are you referring to the sawdust trick? 😎

Bill, yes I realise that the acceptable reading can be reached before you get to the full 140lbft., so I’ll bear that in mind, but I was hoping to do it without removing the diff.
Bernie.
b higginson

Might work. The challenge of doing it in situ could be removing the outer bearing to access the spacer.
Paul Walbran

Depends a bit too on what/when the whine is-
If it's a constant speed related wirring sound the pinion bearings 'could' be toasted from being over tightened-
Have you checked for any freeplay in the pinion at all---maybe the pinion nut has undone itself a bit---as they can sometimes
willy
William Revit

Overtightening the flange nut will not affect the pinion positioning. It will alter the pre loading on the pinion bearings.

Jan t
J Targosz

Backlash is OK. If as Jan says, over tightening the nut doesn’t affect the pinion position, I think I’ll live with it for a bit and get my spare diff rebuilt.
Thanks for the responses.
Bernie.
b higginson

Hi Bernie,

Not that I'm an expert, far from it. But last year's events that led me to have to reset my own pair of diff's, following a bad paid for rebuild, which taught me a few things.

If anything, you wouldn't move the pinion more into mesh, if anything, it would pull further out of mesh; but only if the inner pinion bearing was affected. However, since both bearings are effectively tightened against eachother, there's no relative movement between the crown wheel and pinion.

If your diff wasn't whining before you over tightened the pinion nut, then it's not likely the problem is crown wheel and pinion causing the whine.

The pinion bearings themselves can cause various noises, including whining, if too tight.

I wouldn't drive it too much. If excessively too tight, the pinion bearings won't last too long. If they gwt really bad, then the pinion can start to move, both in and out, and laterally. That will affect the mesh, and could damage both the crown wheel and the pinion.

You 'could' try backing the nut off a tad, and use a punch on the threads to stop it coming looser. Or, best done out of the axle, take the nut right off, and set the preload with a weight sufficient, for used bearings, and use a bit of threadlock (as you won't have 140's worth of torque on the nut). But I reckon you'll still likely have a fair bit, 80/90, and with thread lock/punch, it'll hold.

Better still. DIY. take the diff out. Easy to take out the diff, and then you can put new bearings in. Of course a new seal again too. Taking the bearings off the pinion, isn't that hard at all it turns out, nor is putting the inner pinion bearing back on.

Plenty of pic's and more explanation in my archived (longish 😉) thread.
--- "Diff rebuild 2023. Chapter 2. --"
2023 Technical archive.

The picture is after I tried to grind/cut my inner pinion bearing off. I bought a puller ( circa 20 quid), and it was very easy to pull it off. To put it back, bung the piniinin the fridge for a while, and heat the new bearing (gas hob, or boil it; it'll drop fully home VERY easily.

And for greater assistance, just ask Willy and Paul.🙂.








anamnesis

This thread was discussed between 21/01/2024 and 23/01/2024

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