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What Did You Do To Your Minor Today??

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0123 Mike D
Biddulph, Staffs, UK   GBR
How about putting them back Phil thumbs up

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66jalopy Avatar
66jalopy Silver Member Phillip Jolliffe
Lake City, FL, USA   USA
almost as easy

0123 Mike D
Biddulph, Staffs, UK   GBR
Thanks Phil yawning smiley)

A well worthwhile job then thumbs up

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Midhurst80 Avatar
Midhurst80 Gold Member Bob Killam
Midhurst, ON, Canada   CAN
Had a great day changing the differential from 4.2 to 3.9. Excellent change in drivability.

Hi Bob,

How do you tell if you have a 3.9 differential? The reason I ask is, a fella sold me what he said was a 3.9 diff quite a few years ago for $75 at a swap meet. I'm guessing it is, but how do you tell? I got this before I new anything about Morris Minors just because I read that is what you need. May have been a bad deal since it could be wrong gearing, worn-out, or real noisy and needing a rebuild, but heck, might be OK too, will have to see.
Anyway if anyone can give advise on how to identify what ratio of differential it is, I would be greatly appreciative of any advice.

TX
Mr fixit
Chris smiling smiley

John in Eugene Avatar
John in Eugene Platinum Member John Quilter
Eugene, OR, USA   USA
If it is open and can be viewed, count the number of teeth on the pinion gear and ring gear and divide one into the other. If for example 8 teeth on the pinion and 43 teeth on the ring gear it would be a 5.37 to 1 ratio. 9/41 would be a 4.55 to 1 ratio.

John F. Quilter
Eugene, Oregon USA

0123 Mike D
Biddulph, Staffs, UK   GBR
In reply to # 33830 by Midhurst80 Had a great day changing the differential from 4.2 to 3.9. Excellent change in drivability.

Please would you kindly define and
quantify those changes for us Bob smiling smiley

johnnyw637 Avatar
johnnyw637 Silver Member John Warner
Norwich, Norfolk, UK   GBR
1960 Morris Minor Traveller "Boris 2"
1964 MG Midget MkI "Flying Midge"
1964 MG Midget MkI
I'd guess Mike,
It takes the revs down top end and makes 1st gear more usable?

In the meantime warming up having been out, having at long last started doing something about putting an alternator on in place of the dynamo.

Have a great Christmas Johnny

0123 Mike D
Biddulph, Staffs, UK   GBR
In reply to # 33850 by johnnyw637 I'd guess Mike,
It takes the revs down top end and makes 1st gear more usable? Can you quantify your guess please Jonny smiling smiley

In the meantime warming up having been out, having at long last started doing something about putting an alternator on in place of the dynamo. Good move thumbs up

Have a great Christmas Johnny

johnnyw637 Avatar
johnnyw637 Silver Member John Warner
Norwich, Norfolk, UK   GBR
1960 Morris Minor Traveller "Boris 2"
1964 MG Midget MkI "Flying Midge"
1964 MG Midget MkI
Life's too short matesmiling smiley

I hate working in this ..it's going down my neck...time for another break!!!!
Lunch and finishing job, to get car inside again Mike, but would have thought fairly obvious to a man of your great knowledge.

Cheers Johnny


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0123 Mike D
Biddulph, Staffs, UK   GBR
deleted



Edited 2 time(s). Last edit at 2018-12-14 12:49 PM by Skye.

rlincoln Ray Costa
Gurnee, IL, USA   USA
1963 Morris Mini Traveller "Miss Marple"
John is right, but there may be an easier way. Morris, and later BMC, inscribed the edge of the crown wheel with the ratio. It will look something like "10/39." Sorry, I don't have one handy to take a picture. With the differential in the car, jack up one rear wheel. Put a chalk mark on the tire and another on the drive shaft. With the car in neutral, turn the the drive shaft and see how many turns it takes to rotate the wheel exactly one complete revolution. A little under four times and you have a 3.9. A little more than four times is a 4.22, and a lot more than four times is a 4.55.

I paid too much for a used 3.9 that was worn out, and the only thing to do with it was use it for a boat anchor. I bought another one out of a rusted out Sprite that was in great shape for $50 (along with the rebuildable 1275 engine). My good original 4.55 went to a Bugeye Sprite race car owner. At least they are easy to change.

Midhurst80 Avatar
Midhurst80 Gold Member Bob Killam
Midhurst, ON, Canada   CAN
Mike, as for the ratio Ray stated it was stamped on the diff gear. As for the change, it is a little more complicated, when I bought the car about 10 months ago the tyres had been recently changed to a more common size available in Canada 165 R 14. This ment that the speedometer was reading a little high and the motor revs were higher than comfortable on the highway. The new (to me) differential gearing made the speedometer more “correct” and lowered the revs needed to keep up with traffic on the highway.

0123 Mike D
Biddulph, Staffs, UK   GBR
In reply to # 33864 by Midhurst80 Mike, as for the ratio Ray stated it was stamped on the diff gear. As for the change, it is a little more complicated, when I bought the car about 10 months ago the tyres had been recently changed to a more common size available in Canada 165 R 14. This ment that the speedometer was reading a little high and the motor revs were higher than comfortable on the highway. The new (to me) differential gearing made the speedometer more “correct” and lowered the revs needed to keep up with traffic on the highway.

Thanks Bob thumbs up

So, the change in diff ratio makes your car
more driveable on your highways.
What are typical highway speeds please?

You say you run on 165R14 tyres,
which meant the speedo read high.
Are they low profile tyres please?

Midhurst80 Avatar
Midhurst80 Gold Member Bob Killam
Midhurst, ON, Canada   CAN
Hi Mike, yes to the lower profile tyres. As for the highway, the posted speeds vary a little with the secondary highways, like you’re A and B roads are generally 80 mph while our limited access hwy are 100 and up. A little too fast for “Nelson”. T real speeds are 10% or more above.. just like England and the Natioal speed.

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