Morris Minor Owners Club

My diff is whining like a cat with its tail trapped in a door. I've found a 4.55 diff on ebay but believe this to be a van (or maybe pickup?) diff.
As I understandt it my 1966 1098 uses a 4.22 diff.

Numbers wise they don't sound too different.

Can I use the 4.55 diff without impacting too much on acceleration?
I don't give a monkeys about top speed.

Cheers
jon

BTW: I know I should probably buy a new 4.22 diff but they're blooming expensive!!

It should slightly improve acceleration, but give you a top speed of 70 tops

which isn't much fun. I should know, I have a 1:4,55 diff. Ids bad for fuel consumption too. Nice if you live in an area with hills.
Th highest hill is about a foot or two high, so I don't really need it

When i had a 1098 running a 4.55-1 diff it gave effortless acceleration and
was quite nice to drive but,of course, it was a bit 'revvy', and your speedo
will not read correctly.

Unless you fit a Van speedo. Which I did.

Yes ONNE, but changing the speedo meant that you then had to change
the fuel tank sender unit too in order to get the fuel gauge to work, surely?

Well, no, I have the early type. I know zilch about the later ones

Does it? I didn't know that. Why? One of mine has a saloon tank and, I assume, sender, and I've not had problems with the gauge.
I took the easy option, of course, and own LCVs which come with the 4.55:1 as standard:D

ANDREW.. I raised the point because people do not realise that if,say, you
upgrade to 1098 mechanicals on an earlier car and then fit the matching late
type speedo the fuel gauge will not work correctly. This is because the sender units on pre 1098cc cars are differently configured. This is usually the
last problem people expect when doing all the hard modification work.

Aha - mine were just 1098s, so I guess thet were the same sender units.

when was the change made Willie? are all gold faced speedo's the same?

ONNE, as far as I am aware, there is no problem with fuel gauges and senders up until the introduction of the 1098 vehicles. The complication is that the first two years of 1098 cars still had a bronze faced speedo so some
confusion can arise. This is where the code number on the speedo face comes
in handy, i.e. 1098 bronze speedos are numbered SN4477/80 and the fuel
gauge on these will NOT work with the earlier type tank sender unit. The
further complication is that all early type sender units had a NUT terminal.
but so did the first two years of the 1098 type! All sender units after 1964
had the Lucar push on connector.

Back to the diff question - it will be a bit more revvy - but if you are only doing town work and no long distances it will be fine ! Buy it if it's cheap. But you could try 'wanted' on here! You might even find your top speed goes up a bit - but at the expense of higher revs/more noise/poorer fuel consumption.

Why would your top speed go UP? You'll get 70 max, believe me...

It doesn't BMCecosse, really, 70 is max

What is fuel guage problem - just swap them over, I did. Sure the face is the wrong colour but at least it is the one you know.

Yes, if the engine is a bit more 'revvy' then the top speed will go DOWN.

Willie wrote:The complication is that the first two years of 1098 cars still had a bronze faced speedo so some confusion can arise. This is where the code number on the speedo face comes in handy, i.e. 1098 bronze speedos are numbered SN4477/80 and the fuel gauge on these will NOT work with the earlier type tank sender unit. The further complication is that all early type sender units had a NUT terminal. but so did the first two years of the 1098 type! All sender units after 1964 had the Lucar push on connector.

Right! I'm glad you said that. So there are really 3 types of sender then. early (pre 1098), middle (1098 - screw terminal) and late (1098 - lucar terminal). But the 'internals' of both 1098 types (screw and lucar terminal) are the same and interchangeable then. Gracie is a crossover car (1963) and has a 1098 with a screw terminal sender and I imagined it was the early type. Thanks for the clarification.

Not necessarily - the lower gearing will allow the engine to spin faster and hopefully develop it's full power potential - with the car going faster than before. Many cars including the Minor - are 'over geared' to improve the fuel consumption - and so they reach a balance of power at certain engine revs against wind resistance at that speed. But the engine may not be at it's peak power point - and so lower gearing may allow it to rev faster and so develop more power, and so a higher speed is reached before it balances out again. Many modern cars for example can go faster in 4th gear than in 5th - on a flat road of course! Since the speed limit is 70 anyway - it's hardly relevant in the UK.

Find a mate with a commercial ((4.55 diff). Go out with him in your saloon (4.22). Find a bit of clear road and accelerate to top speed, and see who's going at the highest speed. It'll be you.

bmcecosse wrote:Not necessarily - the lower gearing will allow the engine to spin faster and hopefully develop it's full power potential - with the car going faster than before. Many cars including the Minor - are 'over geared' to improve the fuel consumption - and so they reach a balance of power at certain engine revs against wind resistance at that speed. But the engine may not be at it's peak power point - and so lower gearing may allow it to rev faster and so develop more power, and so a higher speed is reached before it balances out again. Many modern cars for example can go faster in 4th gear than in 5th - on a flat road of course! Since the speed limit is 70 anyway - it's hardly relevant in the UK.

The engine tops out on revs well before the 'wind resistance torque limit' is reached. This is why we are all saying that the 4.22 diff will give you a higher top speed than a 4.55. Simple gear ratios. I have run out of revs with a standard 1098 and 4.22 diff so you definately would with a 4.55!!

I geared my modified car to top out at 130 MPH for maximum revs (7000) using a Ford 5 speed box and a 4.44 diff. This was pretty close as the 'torque wind resistance limit' stopped the car at just a tad over 120 MPH (6500 RPM in 5th)

Many cars will go faster in 4th than 5th you say??? Well, my only experience of that is perhaps a very low powered car such as a 1.0 Fiat Uno going up a bank in a high geared 5th! Along the flat that should not be the case or with a higher powered engine. My Rover will go a LOT faster in 5th than 4th simply because I run out of revs. Not that you should be doing that on our roads but my Rover will do slightly more than 130 MPH in 5th. It can't do that in 4th because it's run out of revs! as is the case with the Minor.