Hi guys,

Is there any way to determine the diff ratio of an engine that is not split?
The engine is not in the car.

I assume it'd be a case of knocking it into 4th gear (1:1) and then turning the engine over? Or something?
Haha too many beers last night. In my head it makes sense but I am not sure whether it will in reality.

Any help appreciated.



WG

If you're lucky there should be a sticker on the diff casing that says what it it.

Otherwise as you say. Take the plugs out, turn the crank with a socket on the pulley end and count how many times the outputs turn, make sure they do so at the same rate.

The other thing: have you ever had it running in a car? What RPM did it do at a given speed?

Pull the plugs, stick it in 4th, mark the tyre and the wheel arch, mark the harmonic balancer, roll the car one complete turn of the tyre while counting how many times the harmonic balancer turns.
3.5 turns is close to 3.44 and 3.65 so you need to watch carefully! (two turns of the wheel and it will be just below or above 7 turns at the crank, it will be near your mark for easier checking!)

Edit, I missed the bit about the engine not being in the car.

If there is no oil in it, just pull the speedo drive cover off.
Put in neutral.
Count the teeth on the pinion and the crown wheel (paint mark one crownwheel tooth first).
18/62 = 3.444
17/62 = 3.647
17/64 = 3.765
16/63 = 3.936 (uncommon)
15/62 = 4.133 (Moke?)
15/64 = 4.26 (Morris 1100)

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Arrrr, sorry Doc....

15/62 = Morris 1100
15/64 = Moke
15/65 = Moke - very very late

if you feel it has a 4.xxx:1 diff, you'll need to turn the engine over at least 8 times to be sure, or pull the speedo drive cover off as the Doc suggests.

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4.133 = UK Morris 1100.
4.26 = Australian Morris 1100.

I dunno what Mokes had!

I have a Morris 1100 box here, and it had a 4.26 in it...
Not that there's much difference- as both are useless in a Mini.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

No, there is nothing you can notice between them in driving them.

I just check the M1100 w/s manual, they do state some pretty odd things in there, with various diff ratios from 3.44, to 3.65 (IMO, they have to be incorrect) and 4.1 and 4.2 ratios. According to that (factory) manual, the 4.26 was fitted to the Ozzy built M1100 and the 4.1 to the 1100S. I used to wreak out a few M1100's - maily for the diffs for our mokes. Every one I pulled down had a 4.1 in it, not to say that they didn't fit 4.26's. They are not a car that I have had a lot to do with and I'm definitely not up to speed on the specifics of them.

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Hey GT,

Later UK ADO16's like the 1300 GT used a 3.65 for sure, not sure about others...

cheers

Kev

Pretty sure ADO16 Austin America (2 door 1300) used the 3.65 too.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

Thanks guys.

That would make for some pretty tall gearing then on the 12's (?) that they ran on. Were they a lower profile tyre, like a 65 series?

Any low-down if they did fit the 3.44's? (shaking head)

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Not sure on tyre size they ran back then (late 60s/early 70s).
Our Morris 1300 auto ran 6.20-12 crossplies I think from memory.
The missus blew one so I recall the size.

Morris 1100 is running the 1368 stroker in his 1100 now with a 3.65 diff, says hills are no bother any more!!

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

The 4.1 and 4.2 were way too under geared for Highway use, they needed to raise the final drive ratio when they got the 1275 motor and more freeways were being built.

The reason that Australia had the 4.2 was because of the driving mentality of the time. Top gear performance was the king back then. You got into top gear and left it there, if your car couldn't get up a hill in top gear it was a useless car! A four speed box was seen as one gear too many by a lot of people.
Never mind that the poor 1100 could only do 72 mph (115kph) at 5000 rpm.

Road speed at 1000rpm
3.44 = 18mph. @ 5000rpm = 90 mph
3.65 = 17mph. @ 5000rpm = 85 mph
3.76:1 = 16.4 mph. @ 5000rpm = 82 mph
4.133:1 = 15.1mph. @ 5000rpm = 75.5 mph
4.26:1 = 14.4mph. @ 5000rpm = 72 mph

The 3.44 was fitted to the early 1275cc powered cars which would mainly have been the MG 1300 exported to the USA.

You interested in selling the CW&P then?

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But would it have enough torque to get there without a dead-flat road and a tail wind?

Final drives are such a balancing act and everyone wants something different. A mate has a 2.75:1 in his SPi Mini and he loves it because it cruises at 3000rpm at 100kph so he can get to Adelaide without filling up (7.5 gallon and 5.5 gallon tanks). I hate it because it accelerates like a slug.

Personally I like something about 3800rpm at 100kph. That's around a 3.44 diff on 10" rims, or in the case of a Moke running 175/70R13 tyres, a 4.1 diff. The rebuilt Mini K box I have put aside for my Traveller unfortunately has a 3.76 in it. 4100rpm at 100kph with a pretty torquey 1275 engine? No thanks!

Cheers,

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Brett Nicholson
Greendale (near Ballan) VIC.
1971 Morris Mini Moke
1966 Austin Mini
1965 Morris Mini Traveller
1973 LR Series 3 88
2007 LR Freelander 2