I have an S gearbox partially dis-assembled (the glass is half empty), the diff is out of it and I want to know how you can tell if the pin needs replacing...

is it one of those "replace it while it's out" type things?

here's a pitcha... there is a shiny spot on it

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did I tell you that I won a trophy?

Don't know about the "when do you do it" bit but since you've got everything apart and on the bench , and it has a shiny section (don't really know if that's good or bad but it show's there is a bit of wear at least to my thinking) so why not replace it while it's out . Also a good chance to look over all the components and bearings . The diff often takes most of the abuse with bigger wheels etc so might as well be nice to it while it's apart .

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As it's a BMC/BL original (which had very poor hardening depth) I'd replace it with a comp one whilst it's out.
Ditto the 2 spider gears- they have been in service for years and the bores would now be worn to match the old pin. And the teeth take a hiding with a Hi-Po 1275 or bigger.

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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.

thought so..... more on the list, lucky I'm not paying

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did I tell you that I won a trophy?

Is it possible to access the pin\ spider gears in the diff without taking the engine out?

No way.
But once out, diff removal is easy- the motor can stay on the gearbox, unless there are other probs to fix.

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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.

$150 for a kit, with a competition pin and new planetary gears - can't really go wrong... so long as I put it back together properly

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did I tell you that I won a trophy?

Personally wouldn't get the up-rated pin, brother fitted one to his standard turbo and then when it needed the engine rebuilding (as they often doo) about 6 months later the up-rated pin was rhubarbed.
Get the Twin cross pin diff from Minispares and never have to worry about it again !

I took the pin out of my 1310S after 70,000 of my hard miles to fit a new one, found it already had an uprated one in there.
I measured it, it had a mere .0005" (1/2 a thou) wear. Good pin...
So, they DO work. Gears good too. This was a few years ago, not sure how good the current crop of comp MiniSpares pins are but I'm running a few now.
At $450 or so a new 4 pin diff is nice, but too exxy for most. Us colonials here are all underpaid by UK standards, obviously...

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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.

I'll treat this one as a learning experiment then... it's for my dad anyway, and he drives like a bit of a girl

the diff in my S is rooted judging by the amount of movement the output shafts have against each other - maybe I'll put a twin pin one in

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did I tell you that I won a trophy?

I've rebuilt a few diffs and found the basket wears on the surface where the two gears run on (the ones on the pin). This places them even further apart and will add to the slop you are already getting from the worn pin.

The trick is to find a good basket then buy a set of the copper cup bearings and new pin, the gears themselves may be ok. The latter style copper bearings have tabs so they don't rotate like the old ones.

Hope this adds to the already helpful info from everyone else

Cheers

McOz
(I'm worth the extra 30 cents)

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Mafs waz not my strong subgeckt at skkol

If you are doing up your old diff, spend 5 mins to grind the hemisphere (diff centre) so the later `tab type' copper washers will fit properly. They are tabbed so they don't spin, which is what wears the old diffs out.
If yours has a wear lip round the pin hole, bin it and find a better one.

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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.

I have to admit that i`m with Smiffy on this one,,,well worth the effort & money if your original diff is rooted to the point where it needs all that (including the wear in the carrier)

you could spend "nearly" the same money repairing the old one as fitting the cross pin type

& much better result for the long term

just what i`d do tho,,, not telling anyone what they should do.

then again,,,it`s a "FEEL" & "LOOK" thing to determine whether it`s worth even bothering to repair it for your old man , especially if he`s just going to putter around in the thing

if it`s a fang car & you`re going to spin the wheels up all the time , then go & buy your self a cross pin assy & never look back.

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No offence intended here but--> anyone writing a book about minis 30 years ago may not have experienced such worn or stuffed-with components as we are finding these days.

You should put your heart & soul into everything you do.

Local pricing (Sydney)-
Twin crosspin diff assy $508.41 (MiniSpares one)

Comp diff pin $51.02
Gears- 2 diff hemisphere $$54.40/pr
Diff copper thrust washers $14/pr
Diff side gear thrust washers $8.74/pr
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Total $128.16.

So, it's $380 more to go for the twin crosspin diff. Nice, but...
Maybe worth it for running big wheels and sticky rubber, but with 10" wheels, for a road car, I'll keep the money thanks...

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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.

what about 10" wheels and sticky rubber for my weekend warrior?

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