I AM going to write this down...!

[Ondergard]

... when someone clues me in!

I can't remember what a standard differential measures for a '69 saloon... so is it 3.77, or something like that?

Also, someone once said something about replacing the standard diff with one off something else, which gives a smoother ride, or transfers more power, or something or other... some kind of advantage, anyway.

SO... could someone tell me

a) what the standard diff measurement is;

b) what the measurement is of the replacement;

c) which car the replacement would come from, usually;

d) would Minor back axle be ok with the replacement diff;

e) what huge advantage makes replacing the diff a good idea?

Sorry to be a pain if all his has been done to death on here before, but I am an ignoramus in engineering terms!

[chickenjohn]

It sounds like you are not sure why you would even want to change the diff.

Is it whining or clunking?? If not just change the oil or top up with fresh EP90 and leave it as it is, the standard Minor diff is fine.

[alex_holden]

The standard diff ratio for a 1098 car is 4.22:1. Some people switch to a diff with a lower ratio so the engine doesn't rev as high when cruising on the motorway. The disadvantage is it makes the car less nippy, especially if the engine is a bit tired.

[mike.perry]

See Series MM website, car ident. for table of gearboxes and diffs http://seriesmm.mmoc.org.uk

[PSL184]

a) 4.22
b) 3.9 or a 3.7
c) Woseley 150, Riley 1.5 or MG Midget
d) Yes
e) More relaxed motorway cruising, less noise, better MPG

[MarkyB]

the diff info is in the Engine Information section not in the Technical Information where you might expect.

I've got a diff question too, are 1963 travellers fitted with the same diff as 1968 saloons?

[alex_holden]

I've got a diff question too, are 1963 travellers fitted with the same diff as 1968 saloons?

I think it depends on the engine; that is around the transition time when 1098s were first introduced. My 1963 trav has a 1098 engine and a 4.22:1 diff. Interestingly it also has a gold face speedo with the early type fuel gauge.

[PSL184]

I've got a diff question too, are 1963 travellers fitted with the same diff as 1968 saloons?

It "should" have a 4.22 diff in. The 1098 engine was introduced in Oct 62 which was the change point from the 4.55 to 4.22 diff...

[PSL184]

Interestingly it also has a gold face speedo with the early type fuel gauge.

I believe this changed in Oct 63 to the black faced speedo.....

[MarkyB]

"Transition time" is spot on, clap hands wipers, gold speedo and 1098 engine (might be original).
I'm going by how they feel to drive, the traveller seems to rev a bit higher for any given speed.
I'll have to crawl about underneath with a rag and a camera to see what number is stamped on it wont I ?
My suspicion is that the engine has been changed in it's long and chequered history.

[charlie_morris_minor]

e) .. better MPG

maybe not.. you have to work your engine harder to accelerate if you get a 3.7 dif

[PSL184]

e) .. better MPG

maybe not.. you have to work your engine harder to accelerate if you get a 3.7 dif

My statement based on the following...... The 3.7 diff will not be any benefit if you only drive around town and never go over 40mph. It will certainly help if you do a lot of motorway miles though.....

[bmcecosse]

The idea behind changing the final drive ratio is to drop the engine revs for a given speed. To maintain that speed - the engine must deliver the same power as before - so now the throttle has to be held further open than before which means a more dense charge going in to each cylinder. Thus the barometric (some call it 'dynamic' ) compression ratio is raised - and the engine burns the fuel more efficiently, supposedly saving some fuel. The engine may also be working more closely to the revs where it develops it's best torque - due to the fixed camshaft timing - it really is a disgrace no-one has come up with fully variable valve timing to optimise engine torque at all revs ! There may also be a worthwhile reduction in engine friction and gearbox drag - because of the lower revs.

[Matt]

it really is a disgrace no-one has come up with fully variable valve timing to optimise engine torque at all revs !

Some of the new alfas now have hydraulic/pneumatic (cant remember) ECU controlled exhaust valve now, so they can do fully variable valve timing on the exhaust...

(or it might be the inlet Mogwai will know...)

[Kevin]

it really is a disgrace no-one has come up with fully variable valve timing to optimise engine torque at all revs !

Some of the new alfas now have hydraulic/pneumatic (cant remember) ECU controlled exhaust valve now, so they can do fully variable valve timing on the exhaust...

(or it might be the inlet Mogwai will know...)

ECU in a standard Moggie whatever next

[chickenjohn]

I think you will get better fuel consumption simply by ensuring your Minor is running as it should. I.E. valves lapped in, ignition set correctly and the mixture set properly, and also driving style has a big impact on fuel consumption.

Go on and advanced driving course!

These two actions- optimising the standard car and the driver will save a lot more fuel than swapping the diff.