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MG Midget and Sprite Technical - Diffapointed

Things haven't gone to plan.

Last year I acquired a 4.55 differential to use on the hills in place of the original 4.22.

The 4.55 had no signs of damage or ill-use but there was too much backlash and a friend offered to re-build it for me.

Acquiring parts was a bit of a saga as, without thinking it through, I ordered bearings etc. for my '67 Sprite. When the message came back that they didn't fit, I realised they should have been early type bearings as for the Morris Minor.

For all sorts of reasons, the 4.55 diff didn't get fitted until last month.

While the performance appeared to be exactly what I was hoping for, the howling from the diff certainly wasn't so, after just 10 miles, it came out and went back for further investigation.

Incorrect torquing of the pinion shaft was diagnosed and and corrected and it was re-fitted.

It didn't make it out of the garage this time as, with the back end jacked up, the howling returned as I ran it up through the gears.

Here's a video of what it sounds like: http=://www.youtube.com/watch?v=20Vuu-dlS9o

Does anyone else have experience of howling diffs?

Any help, advice or hints would be very welcome.

The 4.22 will be going back in this week.

Two small consolations: I can now do a diff swap in under two hours and I also have a set of bearings for the 4.22's rebuild once the 4.55 is sorted!

Colin
C Mee

This link might work better:

http://www.youtube.com/watch?v=20Vuu-dlS9o&feature=youtu.be&fbclid=IwAR1nxN9QqvS6zVMfA8tGODTlFWvpwJkaBH0sb3j2mZLeXwN7vZW7p11avRc
C Mee

Gosh that's awful! more a chatter than a howl to my ear. Given the number of Morris Minors sold the world should be awash with 4.55s - I'd just buy & try another one.
David Smith

Dave- that's rather what I'm thinking unless someone can suggest an achievable solution.

The video definitely sounds chattery - more like a howl from inside.
C Mee

If you can't find a cheap one locally I've 3 or 4 spare...
David Smith

Colin
Couple of things
First off, yeah it sounds a bit less than perfect, but with an open(nonLSD)axle you have to be a little alert to the fact that if running it off the ground like that, if one wheel is spining up quicker than the other you will definatley get noise from the planetry set as they are straight cut gears
If you are going to remove it, it would be worth running it up again with the drive shafts removed, just to double check that the noise is in fact coming from the c/w and pinion-----I'd be doing that first off, then progress on if the noise is still there with the shafts out
Secondly I'd find another helper
Kind as he was to do it for you, the alarm bells are ringing, firstly for not torquing up the pinion and also for giving you back something that sounds like that
I can only guess but I would say the main pinion bearing wasn't seated right in and when you went for your initial drive it moved further into the housing and you gained heaps of backlash and lost preload on the pinion nut-a rookie mistake
Also if the noise IS coming from the c/w pinion, on the video it sounds like the c/w carrier flange could be out of true giving that irregular sound and will need machining--they are prone to cracking causing this housing so a real good clean up and inspection is the go there
'Before' dismantling the diff centre the cause needs to be found so a good measure up of backlash in 4 different spots around the wheel and take some tooth contact readings to see what the tooth pattern looks like
This needs to be done before it's all pulled apart, otherwise you'll never know where you're at
willy
I'm look forward to seeing what you find
William Revit

Colin,

The pinion bearing part numbers depend on whether the differential housing (pumpkin in the US) has the filler in it or not. The design changed in around 1962, and whilst the two designs are interchangeable as a unit, but there are a number of differences within them.

There are exceptions, but most 4.55 are the earlier design, whereas 4.22 can be either.

Richard
Richard Wale

mine made a noise not as bad as yours more a whoosing sound and it turned out to be the carrier flange it had a 10 thou run out, changed it for a spare that was withinn tolerance 2 thou and its now allot quieter
mark heyworth

Hi

Thanks for all the advice and suggestions. All extremely helpful.

The diff is out again and on the bench. I'm more certain than ever that it's pinion related as it makes a 'gears meshing' sort of noise when turned by hand whereas my other two diffs, although having loads of backlash, turn much more quietly.

Dave. I might be interested in taking you up on your offer, so if you'd like to email me at meecclspa at aol.com perhaps we can have a conversation.

Willy. I'm not ready to give up on my chap yet - he's actually very accomplished and just as frustrated as me - he's just more used to Peugeot 205 GTIs than BMC!
I tried it briefly with the half shafts out and the noise was still there. In fact he thought he'd over-torqued the pinion, making it squeal by being too tight. Before it was worked on for the second time, there was some unevenness in the backlash but this is now greatly reduced to be barely noticeable.

Richard. That's precisely the difference I found. This diff has a filler in it and needed the larger pinion bearings, the axle 'pumpkin' has a filler. Incidentally, I'f found a 1966 date stamped on the 4.22.

Mark. I managed a rather Heath Robinson arrangement with my dial gauge which showed a 3 thou run-out, so I guess that's still a possibility.

Thanks again. I'll report back when / IF I manage to make some progress. In the mean-time, the 4.22's sitting under the Sprite waiting to go back in.

Colin
C Mee

Colin
Sounds like it's a mesh problem then if it was still there without the shafts in--at least that eliminated sungear noise so worth doing
My apologies to your man, reading back I may have been a bit harsh on him--sorry--I keep promising to stick to facts but there you go I've done it again--peeed off with myself for that-

Would like to see some tooth markings if you do that one day and c/w backlash reading
Don't forget ,it's best to have a real good inspection and measutre up before you pull it apart while it's exactly as it was in the car
Cheers
and sorry again to your friend
willy
William Revit

I've killed 2 diffs by running them dry. Both sounded like that one, and one ended up with blue teeth. I've learned that if you can hear the diff howl with a helmet on, then that diff is duff. if you can see any wear on the teeth then it'll howl.
Rob Armstrong

Colin dont know if this will help i was looking for somthing else and noticed these

https://www.bullmotifspares.co.uk/product/morris-minor-steering-and-differential/dif110n02/DIF110N02
mark heyworth

This thread was discussed between 17/03/2019 and 28/03/2019

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