Changing a diff whats the best way?
Turbo Mini Forums

I went on a mini run today the moorland coastal run, but got really stressed with my diff. Ive got standard metro turbo setup engine, with a 1litre rebuilt diff, and at 75mph its screeming.

Im supposed to be doing the nurburgring in less than a months time so not long left, but after the ammount of fuel ive used today, and the noise and annoyance of the diff its putting me off!

I have a metro turbo diff, but it has lots of play in it, whats the best way to swap them over? would i be able to drop down the rear of the front subframe and change it?

When ive got the diff out, will i be able to swap the outside big cog on the diff with the one from the metro turbo one?

Thankyou for any help and advice

Previous Engine: 1040cc Morespeed engine, 1275 turbo head T2 Turbo Mirage Manifolds Megajolt
Previous engine: STD metro turbo, megajolt
Drives: 399bananahp (flywheel) Honda Civic Vtec b18c4 T28 Turbo 1968 Mini

Megajolt maps to download: http://www.jamesfawcett.co.uk/cms/index.ph...&gid=3&Itemid=3

Hi,
You can get the diff out, if your housing has bolts rather than studs.
However to change the final drive gearing you need to change the pinion in the box as well :(
AFAIK you'll need to get the powerplant out to do this job :(
Cheers,
Gavin :)

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i just did mine and the pinion gear will come out with the engine in ,you have to get the engine high enough to take off the end cover and then do the job like that , it was easier than the diff swap .

Edited by robert on 1st Jul, 2007.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

i dont understand something though, this is a standard metro turbo engine i have in, and when i took it out of the metro i just took off the diff and put the rebuilt one from my 1litre onto it, and then put it all in my mini. I didnt change any pinion gears? But it still works?

Previous Engine: 1040cc Morespeed engine, 1275 turbo head T2 Turbo Mirage Manifolds Megajolt
Previous engine: STD metro turbo, megajolt
Drives: 399bananahp (flywheel) Honda Civic Vtec b18c4 T28 Turbo 1968 Mini

Megajolt maps to download: http://www.jamesfawcett.co.uk/cms/index.ph...&gid=3&Itemid=3

Maybe that's where the noise comes from?

its not a gearbox noise, its a high revving noise...

Previous Engine: 1040cc Morespeed engine, 1275 turbo head T2 Turbo Mirage Manifolds Megajolt
Previous engine: STD metro turbo, megajolt
Drives: 399bananahp (flywheel) Honda Civic Vtec b18c4 T28 Turbo 1968 Mini

Megajolt maps to download: http://www.jamesfawcett.co.uk/cms/index.ph...&gid=3&Itemid=3

tonite is my first evening off starting 6pm so ill make a start, shouldnt this diff have worked in my engine then??? i was told they just swap over!! whoops!

Edited by jamesfawcett on 2nd Jul, 2007.

Previous Engine: 1040cc Morespeed engine, 1275 turbo head T2 Turbo Mirage Manifolds Megajolt
Previous engine: STD metro turbo, megajolt
Drives: 399bananahp (flywheel) Honda Civic Vtec b18c4 T28 Turbo 1968 Mini

Megajolt maps to download: http://www.jamesfawcett.co.uk/cms/index.ph...&gid=3&Itemid=3

you can swap the diff no problem but you would normaly be expected to swap the crown wheels at the same time. thus leaving the gearing the same.

i know with some final drives you can change the pinion and not the crown wheel, but this is for slight changes in gearing.

i assume the 1ltr diff was a 3.4 so maybe a change from 3.2 is ok?

if you dont like it reving in 4th gear then changing from 3.4 to 3.2 will not make any real change. it sounds like you would be better off with a 2.7 (but there crap)

i drove to Le Mans (500miles each way) with a 3.2 final drive and 10" wheels, cruised along at between 4500 and 5000 rpm all the way with no problems

i have no idea how fast that is but why dont people like reving there minis? i just wear ear defenders

thanks turboshed!! seems ok for slight changes then, just glad i havent damaged anything (again!)

Whats the standard metro turbo diff? I have one here (the one i initially took from the engine) is that a 3.2?

If i put it in would it not make much difference?

I dont mind revving it, and the noise isnt loud, its just the fuel econemy of going to germany i am worried about. for the extra fuel its going to cost about the same price as a x-pin diff!

Previous Engine: 1040cc Morespeed engine, 1275 turbo head T2 Turbo Mirage Manifolds Megajolt
Previous engine: STD metro turbo, megajolt
Drives: 399bananahp (flywheel) Honda Civic Vtec b18c4 T28 Turbo 1968 Mini

Megajolt maps to download: http://www.jamesfawcett.co.uk/cms/index.ph...&gid=3&Itemid=3

You should always change the pinion and crown wheel together if you are changing ratios.

A 3.44 crown wheel would not fit in with a 3.2 pinion. My guess is that the 998 diff has a 3.1 crown wheel on it. All my standard A+ 998s are 3.1.

Even the slight diffence in crown wheel diameter from 3.2 to 3.1 would cause a very noisy gear train.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Axel is spot on, but on this particular ratio, 3.1 and 3.2 I think that the pinion is the same as a matter of fact.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

I think you're wrong on this Axel. This pinion is someething special

do you mean the big cog wheel arround the outside? when i had both diffs side by side they did have the same number of teeth and did look the same, i guess ill find out when it comes out!

but no noises at all from it so thats odd!

Previous Engine: 1040cc Morespeed engine, 1275 turbo head T2 Turbo Mirage Manifolds Megajolt
Previous engine: STD metro turbo, megajolt
Drives: 399bananahp (flywheel) Honda Civic Vtec b18c4 T28 Turbo 1968 Mini

Megajolt maps to download: http://www.jamesfawcett.co.uk/cms/index.ph...&gid=3&Itemid=3

If they had the same number of teeth and looked the sam thenchances are you put back in exactly the same ration as you took out.

Too clear up the Axel & Vegard discussion:
In A series gear sets the 3.6 and 3.7 sets shared the same pinion as did the the 4.1, 4.2 and 4.3
In A+ series gearsets only the 3.1 and 3.2 ratio CWP sets shared the same pinion ( DAM2808 )

Edited by graemec on 2nd Jul, 2007.

I stand corrected. Some fancy gear design.

So what is making feebs diff noisy?

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

sorry late posted.

if its a 3.1 or 3.2 it would still be fine on the motorway at 75mph.

Feebs, how many revs was it doing at that speed?

Edited by Turbo Shed on 2nd Jul, 2007.

Feebs, the "Big Cog " is the crown wheel, the "Small Cog" is the pinion. They are reffered to as the FD {final drive}. The "Diff" is what the crown wheel bolts onto.

Phil.

WWW.TURBO-MINI.COM

Axel,

Feeb's hasnt said his box is noisy.

Just the whole car is reving its tits off at hi speed.

The best way to save fuel is get it set up on a good RR. it will more than pay for itself on a trip like that.

Plus stuff like correct tyre pressures, a service etc.

Hi,
If your mostly road mileage, it may be worth going to 2.9:1?
Cheers,
Gavin :)

VEMs Authorised Installer / Re-seller. K head kits now available!

WB/EGT gauges. Click here for customers write-up

Visit www.doyouneedabrain.co.uk

My Mini build diary

no, theres no gearbox noise at all, the engines really quiet.

Just revs about 4000 i think to keep up with other traffic at about 70-75, ill get the exact rpm and speeds this weekend, i have just finished work now so didnt get chance to go in the garage.

Whats the final drive of a 1990 standard metro turbo diff? I loved the diff in my last metro turbo engine, top speed was about 115 and it sat happy at 80mph

Previous Engine: 1040cc Morespeed engine, 1275 turbo head T2 Turbo Mirage Manifolds Megajolt
Previous engine: STD metro turbo, megajolt
Drives: 399bananahp (flywheel) Honda Civic Vtec b18c4 T28 Turbo 1968 Mini

Megajolt maps to download: http://www.jamesfawcett.co.uk/cms/index.ph...&gid=3&Itemid=3

3.1

Are you sure Iain ? It's 3.2 IIRC ?

WWW.TURBO-MINI.COM

Edited by minimole23 on 3rd Jul, 2007.