Ms Plum runs an 1100S engine exactly as it was lifted from it's orginal home and complete with 4.2 diff, whilst this makes her go like a cut cat to about 80kph, with 10" wheels and 145 tyres she does scream and wheel spin can be a bit of a problem.

I want to keep the 10" wheels and the 145's as she's a bit of a sleeper so no flares allowed, therefore the question is what diff ratio would people recommend I use?

Off the line speed is nice but given where I live I do a fair bit of my toy driving at 80 or 100kph so having a reasonable level of rpm at cruising is probably most important.

Ms Plum runs Cooper S discs already and I'm wondering if I should perhaps look at changing from rubber uni's while the diff is being done, what's the general recommendation atm.... steel uni's or go for pot joints?

Thoughts?

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'62 Morris 850 (Marion)
'65 Mini Delux - sleeper 1275/S discs (Ms Plum)
'69 Vanden Plas Princess 1300
'71 Wolseley 1300
'74 Austin 1300 Countryman
'94 XJ6 Sport 3.2
'04 Rover 75 CDTi

3.44:1 works nice and is easy to find S/H. Most rodchange boxes here used them, apart from the Cooper S.
A 3.1 or 3.2 would be good but were never sold here, you would need to get one her off a Rover front cut (maybe), or import it from UK.

Forget steel unis, fit pot joints whilst the diff is out. More reliable and less power loss.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

+1 on the 3.44. Still zippy but not revving its tits off on the highway.

Pot joints get a thumbs up from me but rubber unis can be fine if they're kept oil free and the rest of the associated setup is in good nick.

cheers

Jacob

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'72 Clubman Van - 1022cc, 295 head, 731 cam - Daily Driver
'69 Morris 1100 S - Dinged by a bus, in shed under repair
'64 Morris 1100 - Early 1100, long term project

Rubber joints available currently are crap compared to the originals.
I'd go the pot joints...

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Thanks guys, Doc did I read recently that the Rover diffs are physically bigger and don't fit in the standard housing without maching? Would this apply to Morris 1100 diff housings too?

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'62 Morris 850 (Marion)
'65 Mini Delux - sleeper 1275/S discs (Ms Plum)
'69 Vanden Plas Princess 1300
'71 Wolseley 1300
'74 Austin 1300 Countryman
'94 XJ6 Sport 3.2
'04 Rover 75 CDTi

No it's the AUTOMATIC CW/Ps that won't fit into a manual box. They are bigger.
A Rover diff is same as the old ones, except:
1. The copper thrust washers have tabs into the diff centre so they don't spin like the old A series ones.
2. The crownwheel & pinion tooth form is a different angle. But they do fit in old boxes fine, as a SET.

[edit] on diff ratios 3.1 and taller (2.95 etc) in old boxes, the 3rd motion shaft bearing retainer often needs machining out a couple of mm to clear the bigger pinion. 5 minute job in a lathe.
Yes this includes the 1100 box.

_________________
DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.