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MG Midget and Sprite Technical - diff size

Have a 1500 mk3 midget. Could someone please explain how I can tell what size diff I have (have 2 extra out of car and don't know what they are!!). Is there a part No stamped on it or is it not that easy. I have been given all the parts for a 5 speed conversion using a ford type 9 gearbox what would be the best diff (if I knew the size ) to use hence the first question Cheers.
s rix

The number of teeth on the crown wheel and pinion IIRC is stamped on the rim of the diff housing just to the right of the nose piece looking from the front.
You'll need to really clean up the alloy as it isn't terribly clear, the figures are about 1/4" high.
Graham.
Graham P 1330 Frogeye

the diff ratio is also stamped on the outer edge of the crownwheel itself where it is far easier to see than the casing; yours will most likely be:
11/41
or
10/39
9/48
etc
David Smith

Divide the large figure by the small figure and you will have your ratio:

Examples from above.....

41/11 = 3.73:1

39/10 = 3.9:1

48/9 = 5.3:1

Mark.
Mark T. Boldry

Graham, Dave , Mark thank you all for your reply
s rix

SR - watch Mark's maths (or is it his fingers?) !
48/9 is 4.2 not 5.3
David Smith

not on my calculator it's not.

Max T

Is it made by Microsoft :)
Graham P 1330 Frogeye

Isn't the 4.22 48/11 -?
Graham P 1330 Frogeye

oops not Mark's maths or fingers, but my eyes :-)
another laugh at my expense !
4.2 is 9/38
there's a 7/37 and an 8/43 both of which are close to 5.3 but I don't think there's ever been a 9/48 ?
David Smith

I was just giving examples of the figures on the previous post.

Anita was pressing the buttons on the calculator.

:-)

Mark.
Mark T. Boldry

You're thinking of 948cc :-)
Max T

s rix:

A posting from the legend that is Guy Weller, back in 2003;

"If the diff you are checking is still on a car, you can work it out by chocking one rear wheel and turning the other. Count the turns of the pinion flange. It may be easier to mark a point on the tyre and turn it through 10 revolutions to get a clearer distinction between the ratios. Easier with 2 people."
Steve Clark

This thread was discussed between 10/10/2008 and 13/10/2008

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