Hi folks,

I managed to slightly pop my head gasket a few weekends ago, 100 miles from home.. Managed to get the car home with a LOT of replacement water for the radiator, pulled the head off, and it's just popped over slightly (no holes or missing pieces, just signs of blow-by between cylinders), so I shoved a new head gasket on, re-did the valve clearances (after mentioning to anto that I was down on power.. d'oh should have thought to re-do the clearances after putting a new head gasket on), and she's running just like she used to.. except after backing off and putting the foot back down, it now blows lots of smoke.. OH, also sitting idling for more than 1-2 minutes causes it to very badly gunk up the plugs.. Compression test done, we've decided I've probably detempered the valve guides or something and it's sucking oil down them, so a head job was in order..

Then I got to and actually tested the engine in my parts car (much to anto's dismay, he's been 'meaning to' test it for a while to put it in his..), and found the compressions are awesome compared to what mine have always been (I've always had 130'ish, this has 190'ish). So decided to use that engine.. But since the gearbox is cactus (doesn't go into second, and the other gears aren't much better), I bought a gearbox off makka. Only problem there is I have rubber uni-joints, and the gearbox from makka has cooper drives (or so we think? round plate with four bolts?).

Since my mini does 100km/h at 3000rpm in 4th gear, which I'm told is quite unusual, I wanted to keep my diff (4.4L/100km on a trip to melbourne and back is awesome++) so I figured the easiest way to solve both problems was to simply unbolt the rear housing and remove the existing diff, and then do the same with mine and drop mine in.. Which Anto quite happily (grin) pointed out this weekend wasn't quite so simple, as I'd have to swap the gear that drives the diff (the one inside the gearbox) as well.. While that's not a HUGE problem, it does mean I actually have to pull the engine off the top of my gearbox, which means my car will actually be off the road for more than a few hours (i.e. it's not just pull old engine out, swap diffs, drop new engine in..)

So I'm wondering a) what diff ratio my car must have to be doing 100k/h at around 3000rpm on the highway), and b) how to identify what the diff ratio on the gearbox I bought from makka is.. I'm hoping (big hope, I know) that it's actually the same ratio, so I can just drop my diff straight on and save a whole lot of trouble..

Any thoughts?

Cheers,

Damien

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_-DG-_
'73 Mini Clubman S

I'd say you have a 2.9 or a 3.2 diff.
The aussie cars were all 3.44, with the coopers 3.7.
There is usually a sticker on the back of the gearbox that will say maybe 18/62.
This tells you the diff ratio.
What type of mini do you have? Some rovers had a taller diff ratio in them from factory.

It's a '1973 Clubman, possibly S... (It has the S badge, but anto says there's some interior things missing so it likely isn't an S..)

Will have a look for the sticker when I get home

_________________
_-DG-_
'73 Mini Clubman S

Theres probably very little chance of it being there, since its so old now and there is more chance of it being removed, faded, damaged, or fallen off.

Clubbies had either a 3.44 (18/62) or a 3.647 (17/62).
Note these 62 tooth gears are not the same...
Ratio (eg 18/62) is marked on side of crown wheel where the bolts are.

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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.

Try this site
http://rcmoc.org/bitsnbobs/coolstuff/Ratios.html

It's excellent. The only thing is it's in miles per hour and not km's but you should be able to work it out.

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1970 Mini Deluxe - 1275, Weber, Clive 346 cam, MS 4-pot slotted discs, Megajolt ignition Now with new improved Mambas... almost on the road
1966 Van with Traveller rear seat conversion
2008 Prado GXL
All in various states of repair...

you don`t have to take the motor off the box to do the job tho,,,

& count the teeth on both gears to find the ratio

easy-peasy

& please don`t do any more work than you have to ,,,if you can help it...& if you do, then please try not to post it here so i can read it & get all frustrated at how you`ve done all this work that you didn`t need to do...ok???



have fun man

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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.

good to see you're learning to use the fullstop, mate...


good,,,, work....

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I don't?? That would be awesome


That would mean having the engine out of the car already.. the reason I was asking what the ratio on my existing diff would be, is so I can kind of try and plan my timings, being that I want the car off the road for as short a time as possible.. AKA if the new and old diff's are the same ratio, then I can do it this sunday.. if not, I'll have to do it the following weekend, cause it's more than a one-day job (bearing in mind that because of medical reasons I don't get more than 3-4 hours of hard (aka engine-lifting/bending/under car) labour time a day..) so will need both saturday and sunday..

Cheers,

Damien

_________________
_-DG-_
'73 Mini Clubman S

Ahh, well this gearbox has a 15/65 in it.. Going on the site that Dave posted, I'd say I have 20/59 (2.95:1) (cause I'm doing 100 at 3krpm and ~130 at 4krpm)

So looks like i'm swapping that drive gear, so I'll budget the weekend for the changeover..

Thanks guys

_________________
_-DG-_
'73 Mini Clubman S

4.33 ?

How, pray tell, do I get the gear out without taking the motor off?

Cheers,

Damien

_________________
_-DG-_
'73 Mini Clubman S

I THINK he meant you don't have to take the motor off just to check the ratio...

OK...
After you have pulled the diff out, remove the speedo drive end housing, and the selector shaft if it's a remote box.
knock back the lock tab on the pinion gear CAREFULLY with a SFH and chisel. Don't slip and hit the gear teeth...
Then you need to lock it in 2 gears. If remote box it's easy, just move top selector rod outwards (1st) and middle one in (4th).
If rod change you need to rotate the selector sleeve out of the way, then pry the forks into 1st and 4th thru the diff opening in the case.

You can then undo the pinion nut with a long 1-1/2" socket and breaker bar.

It's possible to use a rattle gun to undo the pinion nut but never ever use it to tighten... you can break things and have no control of torque applied.

Don't forget to knock lock tab back up...

Personally I would rather rip the motor off, easier to see what you are doing...

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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.

Ahhh!

Awesome, thanks

The engine is off the *new* gearbox, so that's an 'easy' one, but I really don't want to have to pull the 'dead' engine off the 'dead' gearbox just to get that one gear out Sounds like it's not 'too much' hassle doing it with the engine on the gearbox, so I'll at least give it a burl that way first

Cheers,

Damien

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_-DG-_
'73 Mini Clubman S