Diff identification

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jagnut66
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Diff identification

Post by jagnut66 »

Hi,
I mentioned in an earlier post that I had a very positive driving experience bringing Sally, my Series 2, back from East Croydon and that I was both surprised and impressed with how well she kept pace with modern traffic on the M1 motorway (once we'd escaped the traffic jams in London and the M25, plus the start of the M1), achieving an average speed of between 65 and 69 mph (on a motorway with a good run at the hilly bits mind you).
This being registered on an app on my phone, as the one thing not working was the speedo (dodgy cable).
I remarked that this was even more remarkable, as the top speed of an 803cc car was meant to be only 63 mph.
It was then suggested to me that the diff had probably been changed.
Well, whilst going through the car and replacing the rear axle I put the diff to one side to clean up and see what was stamped into it, I expected to find it was a 948 diff. However on cleaning it up I find I cant see this on the guide to diff sizes I found on here.
It appears to be stamped 8.39 T??
There is also some pale blue paint, under the black paint (and gunge) that I cleaned off, though that may just be a previous owners fancy....
I've attached images for people on here to look at, I'm sure one of you can put me right.
Many thanks,
Mike.
Gearbox attached to 803   1.JPG
Gearbox attached to 803 1.JPG (433.95 KiB) Viewed 1496 times
Gearbox attached to 803   2.JPG
Gearbox attached to 803 2.JPG (1.24 MiB) Viewed 1496 times
Gearbox attached to 803   3.JPG
Gearbox attached to 803 3.JPG (739.81 KiB) Viewed 1496 times
Gearbox attached to 803   4.JPG
Gearbox attached to 803 4.JPG (1.17 MiB) Viewed 1496 times
Gearbox attached to 803   5.JPG
Gearbox attached to 803 5.JPG (1.02 MiB) Viewed 1496 times
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
philthehill
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Re: Diff identification

Post by philthehill »

Diffs Ratios and Pt Nos.jpg
Diffs Ratios and Pt Nos.jpg (982.73 KiB) Viewed 1487 times
The 8:39 diff was fitted to the A35 van.

As BMC were well known for giving part numbers, especially casting numbers one up on the actual part number I would suggest that the diff carrier shown as ATA7033 is actually part number ATA7032.

oliver90owner
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Re: Diff identification

Post by oliver90owner »

That is what I thought, but couldn’t quite correlate(?) how fast that engine must have been revving to average over 65mph!
ampwhu
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Re: Diff identification

Post by ampwhu »

in regards to the A35 van, on mine it has a 4.2 as the engine is a 1098. This would be the same as a Traveller and the saloons near the end of production I suspect. (my A35 van is 1963).

so in regards to the A35 van having a 4.8, that would be the very last vans built which had the 848cc engine.
philthehill
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Re: Diff identification

Post by philthehill »

As far as I am aware the A35 van had the 4.8 diff when fitted with the 948cc engine.

ampwhu
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Re: Diff identification

Post by ampwhu »

philthehill wrote: Sat Apr 25, 2020 4:42 pm As far as I am aware the A35 van had the 4.8 diff when fitted with the 948cc engine.
quite possible. the saloons had the 4.5, same as the MM with a 948cc engine. confusing I know....
philthehill
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Re: Diff identification

Post by philthehill »


jagnut66
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Re: Diff identification

Post by jagnut66 »

Wow, so I was running a very odd diff (for a morris minor) indeed.
I have to say she performed well with it and wasn't unduly noisey, so I'd never of guessed.

The below came out of the other early axle I have lying around. it seems to state 9/44, what do others think?
Early diff 1.JPG
Early diff 1.JPG (1.3 MiB) Viewed 1446 times
Early diff 2.JPG
Early diff 2.JPG (1.36 MiB) Viewed 1446 times
Both diffs have cleaned up well and are not showing any undue signs of wear, indeed I can personally vouch for the first one! :D
So I will have a look round and see what they are worth, price them a little lower and try and claw some cash back from them.

Therefore I am now left with two early axle casings, stripped of all bolt on parts, that require a clean up and refresh (they are covered in a black underseal type gunk).
I would offer them free of charge, as is, to anyone who wants them.
But does anyone want one or both?
If someone does, I can hold onto them until after the lockdown, so they can be collected. I am located in Mansfield, Notts.
Or do they go to the scrap man?
Best wishes,
Mike.
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
philthehill
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Re: Diff identification

Post by philthehill »

The 4.8 diff is well sought after.

The diff ratio does indeed look to be 9/44. To confirm I would count the teeth on both crown wheel and pinion. Please post your findings/count on here.

There were special on off diffs made by BMC/BL special Tuning so the list of diffs in the chart above is not exhaustive. The above list is for standard applications.

As regards the axle casings - if the axle spring mounts are rust free they are worth keeping.

jagnut66
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Re: Diff identification

Post by jagnut66 »

The diff ratio does indeed look to be 9/44.
I shall do that for you tomorrow.
As regards the axle casings - if the axle spring mounts are rust free they are worth keeping.
To be honest there is a small amount of welding needed, however in between repainting the newly cleaned (de-gunked) diffs, I thought I would give the casings a little TLC and ended up cleaning them off (a little more OCD than TLC there methinks :lol: ), which is how I now know the casings need a little welding (so much for the old underseal gunk - but then we knew that anyway, didn't we....).
I shall get this done and then they can go on my 'free to who needs it' pile at the next national (remember them).
While I was cleaning the gunk off them I noticed the below, the 803 casing has a different opening in it for the half shaft than the later one, or was this common knowledge?
Apeture difference.jpg
Apeture difference.jpg (2.98 MiB) Viewed 1410 times
The other thing to note are the essentials in any refurbishment / restoration, some may be more obvious than others..... :wink:
Essentials 1.JPG
Essentials 1.JPG (1.28 MiB) Viewed 1410 times
Essentials 2.JPG
Essentials 2.JPG (565.61 KiB) Viewed 1410 times
Both diffs are now undergoing the final stage of refurbishment, namely a coat of good old Halfords satin black, although it looks more 'glossy' in the photo, as it has just been applied.
Once they have had a second coat tomorrow they will go up for sale.
From what I've seen the 4.875 diff is worth £175 ONO but correct me if I'm wrong?
Best wishes,
Mike.
Refurbishment.JPG
Refurbishment.JPG (963.08 KiB) Viewed 1410 times
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
jagnut66
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Re: Diff identification

Post by jagnut66 »

The diff ratio does indeed look to be 9/44. To confirm I would count the teeth on both crown wheel and pinion. Please post your findings/count on here.
Hi Phil,
The counts is in and (disappointingly) I think this is a standard 4.55 diff, as we have 9 teeth on the pinion and 41 on the crown wheel.
It looks like someone had a stuttering stamp! :P I say this, as I take it from my count that it should have read 9/41.
So no interesting special order then.

I did find one more thing of interest on the 4.875 diff, what appears to be a date stamped into it:
It appears to read '22 9 54 t' (22nd September 1954), which if that is correct would date it to the year of my cars construction but I thought that was too early for a 4.875 diff, unless that was special order? And does the 't' signify anything?
Can someone confirm or otherwise?
Best wishes,
Mike.
Attachments
4.875 Diff date stamp.JPG
4.875 Diff date stamp.JPG (792.77 KiB) Viewed 1358 times
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
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geoberni
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Re: Diff identification

Post by geoberni »

I know this original post is a couple of years old, but I thought I'd contribute my findings.
I've been under the car, cleaning off the Diff to see what the external numbers read.
Basil is a SII, but as some of you may remember, has at some time past been given a replacement engine (wrongly identified by a garage as 948, actually a 1098) and the gearbox was rebuilt as a 948 in the 803 case....
So I wondered what the Diff/Axle might be....
.
220730_153351.jpg
220730_153351.jpg (74.38 KiB) Viewed 697 times
it looks like it's an 8/43 with a 'T' as Mike found on his.....
From the chart earlier on this discussion, supplied by Phil, it seems to be from a GPO van????
Although look at the link over to the A35 Owners, it seems the 8/43 was used there...

The Diff Carrier seems to be an ATA 7033, the same marking as Mike's...??
.
220730_164421.jpg
220730_164421.jpg (54.89 KiB) Viewed 697 times
.
So does this explain why top speed seems to be around 55mph with the engine screaming a bit?
Basil the 1955 series II

Image
ManyMinors
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Re: Diff identification

Post by ManyMinors »

Divide 43 by 8 and you get 5.375 which is the standard ration for a Series11. :wink: .
A pretty useless final drive in a roadgoing 1098 engined Minor but quite sought after by hillclimbers :)
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geoberni
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Re: Diff identification

Post by geoberni »

Dohh
Now you've said that I just looked it up.
The manual says 8/43 axle, I should have looked there instead of just referring to the earlier table.
Well at least I know that's something that wasn't changed... :wink:
Basil the 1955 series II

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jagnut66
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Re: Diff identification

Post by jagnut66 »

Well at least I know that's something that wasn't changed...
Considering you now have a 1098 fitted though Berni it might drive better if it had been changed.
I think if people upgrade the engine (especially if they jump from an 803 to a 1098) then they need to go the whole hog and change everything else to suit.
Otherwise they won't get the best out of the car / replacement engine. Plus the original items left on may well wear out allot faster, or even fail suddenly whilst you're out and about.
At least Berni's gearbox was rebuilt, albeit not to 1098 spec.
Best wishes,
Mike.
1954 Series 2: 4 door: "Sally" -- Back on the ground with (slave) wheels and waiting to be resprayed......
1970 Triumph Herald 1200: "Hetty" -- Driven back from Llangollen in Wales (twice.....)
myoldjalopy
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Re: Diff identification

Post by myoldjalopy »

And yet..............948 engine and gearbox plus SII diff = still able to cruise nicely at 60mph but with pretty nippy acceleration too! 8)
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