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| Close Ratio Gears https://www.ausmini.com/forums/viewtopic.php?f=5&t=56377 |
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| Author: | Super-mini [ Mon Aug 24, 2009 10:21 pm ] |
| Post subject: | Close Ratio Gears |
i currently have a fully rebuilt remote change box and 3.4 diff with comp diff pin. i was thinking of running a 2.9 FD but keeping it together with close ratios and using a quaife ATB LSD where do i get the gears from and how much are they? straight cut or helical? do i buy them as a set or replace individual gears on my set? will i need to run an A+ or rod change box? -thanks 
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| Author: | drmini in aust [ Mon Aug 24, 2009 10:30 pm ] |
| Post subject: | Re: Close Ratio Gears |
Super-mini wrote: i currently have a fully rebuilt remote change box and 3.4 diff with comp diff pin.
i was thinking of running a 2.9 FD but keeping it together with close ratios and using a quaife ATB LSD where do i get the gears from and how much are they? straight cut or helical? do i buy them as a set or replace individual gears on my set? will i need to run an A+ or rod change box? -thanks If you mean close ratio gears for racing, not just Cooper S ratios, they are all straight cut these days. Minispares sells them, so do Minisport UK I think. You can get em for 3 synchro, 4 synchro remote or rodchange, or A+ boxes. You will have trouble getting off the line with a 2.9 diff in it. If you mean Cooper S ratios, you just change the 1st motion shaft and cluster gear in your box. Karcraft sells them, so do most Mini places. Or bring em in from Mini Spares UK. |
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| Author: | simon k [ Mon Aug 24, 2009 10:36 pm ] |
| Post subject: | Re: Close Ratio Gears |
Super-mini wrote: i was thinking of running a 2.9 FD but keeping it together with close ratios and using a quaife ATB LSD
is the 2.9 diff on the cards because you want to drop your revs for cruising? close ratio gears just lift the ratios for 1st, 2nd & 3rd, and put less of a change in engine speed between them, top gear remains 1:1. So when you go to a 2.9 diff, your 1st gear is already taller, and a CR 1st gear makes it taller again. Higher speed, less kick in the backside Stock ratios: 3.64, 2.18, 1.42, 1 ; Close ratio: 3.32, 2.09, 1.35, 1. taken from here: http://www.minimania.com/web/Item/c-ajj ... Detail.cfm |
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| Author: | Super-mini [ Mon Aug 24, 2009 10:59 pm ] |
| Post subject: | |
ahh i did not realise c/r gears would make it worse with a 2.9. what do you think about a 3.2 with c/r gears? what is your feeling about cooper S ratios vs aftermarket? i dont think i can handle the noise from straight cut gears but will my helical gears survive my 100+hp at the wheels? i am also thinking of binning the re-13-T for a sw5, so that might help me get off the line? i know im asking a lot of questions but thanks for your help 
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| Author: | willy [ Mon Aug 24, 2009 11:04 pm ] |
| Post subject: | |
willy's recommendation: Stick with a 3.44 or 3.2 if you really have to : 1 ratio diff. Combined with the close-ratio gears (Cooper S or nearest equivalent), you'll not be revving the ring off it on the highway and it'll still give you great pickup from down low... well, I assume. Who knows what the motor is like to drive, irrespective of the gearing ratios. Yes you will be fine with the "100+" horsepowahhhzzz going through the helical gears. It's torque that shears teeth of gears. And arsebean driving. I know which one you have a lot of
Put the SW5 in if you want it to behave like a "normal" car, but... where has all the fun gone?! |
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| Author: | simon k [ Mon Aug 24, 2009 11:13 pm ] |
| Post subject: | |
Super-mini wrote: i am also thinking of binning the re-13-T for a sw5, so that might help me get off the line?
my suggestion is to give GR a call and explain what you don't like about the RE13, the way you like to drive, and he might have a good suggestion for an alternative... he and I came to the conclusion that RE13 doesn't suit my driving style... so I've got a different cam now |
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| Author: | Super-mini [ Mon Aug 24, 2009 11:34 pm ] |
| Post subject: | |
im gonna fit a megajolt also, this might help get the idle to work. otherwise the re-13 is fine. and i'd guess it would work a lot better with close ratio gears. as it is now, my 1st gear is almost useless so i'd love a longer 1st gear. i'll have to have a chat with my mechanic about what he can do
thanks guys |
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| Author: | TheMiniMan [ Mon Aug 24, 2009 11:42 pm ] |
| Post subject: | |
100Hp -->At The Wheels??? that will pull a 3.2 no problem,,, but a 2.9,,,Mmmm i`d say you`d loose tooo much of that grunt with a 2.9 & it won`t want to rev out well enough in top gear |
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| Author: | wobbles_55 [ Mon Aug 24, 2009 11:51 pm ] |
| Post subject: | |
Helical gears are stronger than straight cut gears...... the have more surface contact, than straight cut gears..... They do zap a little HP but so does being fat........ There was an Nc Mini running here in SA that ran a coopers S ratio helical gearbox and holds the Nc Mini lap record......... and that time was set six odd years ago.............. Keep the RE13, just learn to drive with it..... |
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| Author: | MINImal effort [ Tue Aug 25, 2009 6:53 pm ] |
| Post subject: | |
This site has a great little caclulator for playing around with gearsets and diff ratios.... http://www.guess-works.com/Gearbox/Technical/ratio.htm Will show the effects of speed @ x rpm - but not about how well it will start off the line. 
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| Author: | simon k [ Tue Aug 25, 2009 7:42 pm ] |
| Post subject: | |
Super-mini wrote: im gonna fit a megajolt also, this might help get the idle to work.
it will - from what I experienced sticking it straight on an NA RE13 it gave it a lot more driveability at low RPM |
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| Author: | Super-mini [ Tue Aug 25, 2009 7:59 pm ] |
| Post subject: | |
great this sorts out all the questions i had.
i think i should go with a 2.9 diff but retain my std gears. this will give almost identical 1st, 2nd and 3rd ratios to a 3.1 with close ratio gears but give a slightly longer top gear. in 4th: at 60kph it will be 1950rpm and at 100kph it will be approx 3150rpm the 3.1 with c/r is 60kph=2000rpm and 100kph=3350rpm btw i am running 165/70 R10 |
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