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| Calculating diff ratio - engine not split https://www.ausmini.com/forums/viewtopic.php?f=2&t=73993 |
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| Author: | willy [ Sun Nov 06, 2011 6:08 pm ] |
| Post subject: | Calculating diff ratio - engine not split |
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 |
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| Author: | Harley [ Sun Nov 06, 2011 6:13 pm ] |
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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? |
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| Author: | Morris 1100 [ Sun Nov 06, 2011 6:18 pm ] |
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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.
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| Author: | drmini in aust [ Sun Nov 06, 2011 6:35 pm ] |
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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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| Author: | GT mowog [ Sun Nov 06, 2011 6:47 pm ] |
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drmini in aust wrote: 15/62 = 4.133 (Moke?) 15/64 = 4.26 (Morris 1100) 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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| Author: | Morris 1100 [ Sun Nov 06, 2011 6:57 pm ] |
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4.133 = UK Morris 1100. 4.26 = Australian Morris 1100. I dunno what Mokes had!
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| Author: | drmini in aust [ Sun Nov 06, 2011 6:58 pm ] |
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GT mowog wrote: drmini in aust wrote: 15/62 = 4.133 (Moke?) 15/64 = 4.26 (Morris 1100) Arrrr, sorry Doc.... 15/62 = Morris 1100 15/64 = Moke 15/65 = Moke - very very late 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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| Author: | GT mowog [ Sun Nov 06, 2011 7:08 pm ] |
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drmini in aust wrote: GT mowog wrote: drmini in aust wrote: 15/62 = 4.133 (Moke?) 15/64 = 4.26 (Morris 1100) Arrrr, sorry Doc.... 15/62 = Morris 1100 15/64 = Moke 15/65 = Moke - very very late 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. 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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| Author: | rathcoole [ Sun Nov 06, 2011 7:49 pm ] |
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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 |
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| Author: | drmini in aust [ Sun Nov 06, 2011 8:09 pm ] |
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rathcoole wrote: 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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| Author: | GT mowog [ Sun Nov 06, 2011 8:15 pm ] |
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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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| Author: | drmini in aust [ Sun Nov 06, 2011 8:25 pm ] |
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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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| Author: | Morris 1100 [ Sun Nov 06, 2011 8:42 pm ] |
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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. |
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| Author: | GT mowog [ Mon Nov 07, 2011 5:35 am ] |
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drmini in aust wrote: 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. You interested in selling the CW&P then? |
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| Author: | bnicho [ Mon Nov 07, 2011 8:24 am ] |
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Morris 1100 wrote: Road speed at 1000rpm
3.44 = 18mph. @ 5000rpm = 90 mph ... 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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