Close Ratio (cooper S/1300Gt) Gears in A+ Box.
Turbo Mini Forums

There seems to be general consensus that Pre A+ Gears are stronger than A+, especially the cooper s/1275gt and 1300gt close ratio gears (this is debatable). I have recently aquired a 1300gt box and will putting all the bits in an A+ Box, to avoid the extra hole in the retaining cap, causing cracks accross the web. I have found a link to a doc written by Keith Calver on how to do this, however i will also document the entire process and post up here once finished.

Incase your wondering, ill be running this box with a 2.95 4pin diff, sc drops (non roller) in my Turbo Engine, which should be running between 8-10 psi of boost.

Im trying to find a cost effective way of building an A-Series box that can take a bit of stick, without making your wallett sweat obviously!

If anyone has any tips before i undertake this, they are welcomed!

Cheers

Mike

Copy and paste the link as its a strange one!

"without the brackets"

[http://www.minimaniauk.co.uk/web/SCatagory/GEARBOXES/DisplayType/Calver's%20Corner/DisplayID/872/ArticleV.cfm]

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


Fibreglass Parts? - http://www.tdkracing.co.uk/
Split Rims? - http://www.force-racing.co.uk/

It's easy. Just fit all the gears and shafts from the A box into the A+ casing. That's how easy it is :)

Nice one! Ive rebuilt a box not long ago and was suprised how easy it was tbh.

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


Fibreglass Parts? - http://www.tdkracing.co.uk/
Split Rims? - http://www.force-racing.co.uk/

and use the right bearings to match the gearkit

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Which do you mean Joey, the main bearings or the gearones?

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


Fibreglass Parts? - http://www.tdkracing.co.uk/
Split Rims? - http://www.force-racing.co.uk/

use the bearings to match the gearset/cluster rather than the casing

in your case A series bearings to match the A series gearset

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Reet i see!

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


Fibreglass Parts? - http://www.tdkracing.co.uk/
Split Rims? - http://www.force-racing.co.uk/

I am collecting the parts to do the same as all my searching (here and other Mini forums) suggest the Pre A+ gears are stronger and I don't want to go the (expensive) straight cut way.

Not sure if I believe the GT set are better still (a slightly larger 1st motion gear for one tooth extra, but a slightly smaller layshaft matching gear diameter probably cancel each other out, unless the material is better?) but I've acquired a set of Pre A+ in both standard and GT ratios until I decide.

The question I would add, is does the same "concensus" apply to the diff crownwheel and pinion ???

The reason for asking is, as far as I can tell, for "standard" components, the highest diff ratio available in Pre A+ is 3.44 and for anything higher (ie, a lower number), only A+ gears are available.

Rod.

Schrödinger's cat - so which one am I ???

I dont think its the diff gears that are the issue here, its the diff casing, generally people buy the minispares diff and use exsisting crown wheel and pinion. I will be running the MS diff and 2.95 cwp.

1/4 Mile 14.3secs 96Mph Terminal 10psi of boost.


Fibreglass Parts? - http://www.tdkracing.co.uk/
Split Rims? - http://www.force-racing.co.uk/

You can get the 18tooth input gear with an A+ "hole" in it to use with an A+ mainshafts as well. I know, I've got one.

However, as A+ mainshafts seem to be made from fudge, I'd prefer the old A ones.

Why not buy from Minispares?

http://www.minispares.com/Product.aspx?pid=35934

For A+ mainshafts.

PS: If you buy the two bits one and one, that's cheaper than the gearkit!

Edited by Vegard on 27th Nov, 2007.

By diff casing, I assume you mean the cage or diff itself, ie to use a cross pin type?
I'm intending to use a cross pin one (just searching the forum at the moment to confirm which it is that has the pins NOT at 90 degrees), but, I've seen photos somewhere on this forum (or maybe it was somewhere else) of stripped crownwheel and pinion teeth too. Hence I'm wondering whether to stick with pre A+ for them as well.

Schrödinger's cat - so which one am I ???

Vegard,

The set of GT gears I have acquired is on a main shaft with the 18mm end (ie, like an A+) but are most definately PRE A+ gears.

I thought the later 4 synchro boxes (before A+) had already gone for the larger shaft nose size, or have I (unintentionally) got the Minispares bits you refer to ?

Edited by Rod S on 27th Nov, 2007.

Schrödinger's cat - so which one am I ???

I think that you've got the Minispares kit. I've never heard of this before. Anyway, I guess they used what was in the shelves in the early 80ies.

However, as far as I know, there were never any cars sold with the CR kit in the 80ies and 90ies? When did the 1275GT quit selling?

i have just fitted an 'A' series gear kit in an A+ casing and i had to grovel a small amount of material out the casing as the 'A' series shaft is longer.

Basically where the idler bearing is there is a kind off groove in the casing which i just made bigger.

Other than that a direct replacement :)

I built two this way and had to grind the a+ casing to put pre A+ gears in it.
if your looking for a gearset with A gears on A+ shaft look at early a + blocks with borck & beck clutch set up it'll grow your chance to find this gears:shaft combinaison