flak monkey
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| posted on 19/5/09 at 01:36 PM |
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Recommend me a diff ratio
Probably going to swap to an LSD when I do the Duratec too, the question is what ratio diff do I go for?
I have a 3.92 open diff fitted at the moment with the pinto which seems nice, 3000rpm is 60mph in 5th.
I am changing the box for a HD one with longer first which will make that more useful.
Having said that the most common 7" LSD seems to be 3.62. Which is obviously going to lower my cruising rpm (good for economy) but its going to
have a negative effect on the acceleration...
So what would you do?
David
Sera
http://www.motosera.com
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blakep82
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| posted on 19/5/09 at 01:37 PM |
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i would go for the 3.62 myself i think.
if its a tracky car on a narrow twist circuit, where acceleration is key then its a different matter.
on a road car, what do you really need the acceleration for? nothing really. i'd go for lower fuel consumption
[Edited on 19/5/09 by blakep82]
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IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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Howlor
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| posted on 19/5/09 at 01:44 PM |
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quote:
Originally posted by blakep82
on a road car, what do you really need the acceleration for? nothing really. i'd go for lower fuel consumption
[Edited on 19/5/09 by blakep82]
Erm, traffic light drag racing
Running away from the Fuzz
Out accelerating your lovers husband
Rolling your can of lager back from the bottom of the footwell so you can grab it again.
To name but a few!
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blakep82
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| posted on 19/5/09 at 01:47 PM |
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quote:
Originally posted by Howlor
quote:
Originally posted by blakep82
on a road car, what do you really need the acceleration for? nothing really. i'd go for lower fuel consumption
[Edited on 19/5/09 by blakep82]
Erm, traffic light drag racing
Running away from the Fuzz
Out accelerating your lovers husband
Rolling your can of lager back from the bottom of the footwell so you can grab it again.
To name but a few!
hmm, true... but these are all things i only come accross on a weekly rather than daily basis. except 2 and 3. they're more twice weekly 
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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omega0684
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| posted on 19/5/09 at 01:54 PM |
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i run a 3.62 cossie LSD and i get about 2800rpm @ 60
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coozer
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| posted on 19/5/09 at 02:17 PM |
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I have a 3.62 on my ST170 and it runs out of gears too easy.
Not sure if its the crap gear box ratios or the diff but I'm after a 3.38 to help cruising.
1972 V8 Jago
1980 Z750
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mcerd1
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| posted on 19/5/09 at 02:35 PM |
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what ratio's are you thinking about in the HD box ?
and what size tyres are you running with ?
I've got a BGH E8 box with 0.86:1 5th gear, 3.92 LSD and 245/45R16's
of course haven't finshed building it yet, but gear calc gives me 2755rpm in 5th @ 60mph and 3214 @ 70mph
so maybe not the best for fuel economy
(ps - Alex, just to split hairs, I think your is a 3.64)
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flak monkey
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| posted on 19/5/09 at 03:09 PM |
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quote:
Originally posted by mcerd1
what ratio's are you thinking about in the HD box ?
and what size tyres are you running with ?
I am running 15" wheels with 195/50 tyres at the moment. Gearbox ratios will be standard type 9 other than a longer 1st gear.
I get just over 30mpg from the pinto even with the 3.92 diff when cruising, so I dont think its going to be a major problem. But should I go to the
hassle of trying to find a 3.92. I dont know how much impact it will have on acceleration given the fact that I cant get traction off the line at the
moment in 1st or 2nd and thats with only 160bhp.....
David
Sera
http://www.motosera.com
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bimbleuk
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| posted on 19/5/09 at 03:10 PM |
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I did have a 4.44:1 diff in the back not long a go which was great with the NA 1.6 I had in it at the time. Superb acceleration in any gear but did
cruise at 5000 which was tiring.
When I upped my power significantly ~270BHP) the 4.44:1 was totally impractical on the road just ran out of gears and sat on the limiter. For the best
acceleration/cruise compromise the 3.92:1 is hard to beat. I did some simulations with a 3.62:1 diff and concluded the 0-60 times weren't that
different. However the 3.92:1 diff was up to 2.0secs quicker doing 30-50 or 50-70 mph in gear acceleration tests which is what you want on the
road.
I'm using a BGH E7 HD box with a taller 1st and shorter 5th to close the gears up.
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mcerd1
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| posted on 19/5/09 at 03:33 PM |
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quote:
Originally posted by flak monkey
I am running 15" wheels with 195/50 tyres at the moment. Gearbox ratios will be standard type 9 other than a longer 1st gear.
195/50R15 with a 3.92 diff and 0.82 5th gives you:
3335 @70
2858 @60
and with a 3.62:
3080 @70
2640 @60
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NS Dev
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| posted on 19/5/09 at 07:55 PM |
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I use a 3.62 lsd on my XE (you know the spec and power etc by now lol)
Its great for a road car.
I have a 3.92 CWP which I was planning to fit, but haven't got round to it, and to be honest I'm not sure it will make much
difference.........
Maybe a touch in the 3rd gear area, that's really the only gear where the engine is under load for enough time to think about it at all, and
where the speed isn't so high that brakes are the main consideration, if you see what I mean!
I'd go for a std 3.62 lsd from an XR4x4 v6, and hang onto your 3.92 diff, then you can always swap CWP's if you decide you need the
gearing a touch shorter, btu I doubt you will with a duratec used principally on the road.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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flak monkey
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| posted on 19/5/09 at 08:02 PM |
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Thanks Nat, good advice there.
Are the CWPs interchangeable between the diffs then? Didnt think of that.....
Sera
http://www.motosera.com
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mcerd1
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| posted on 19/5/09 at 10:09 PM |
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quote:
Originally posted by flak monkey
Thanks Nat, good advice there.
Are the CWPs interchangeable between the diffs then? Didnt think of that.....
all the 7" CWP's are interchangeable
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flak monkey
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| posted on 24/5/09 at 01:57 PM |
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quote:
Originally posted by mcerd1
quote:
Originally posted by flak monkey
Thanks Nat, good advice there.
Are the CWPs interchangeable between the diffs then? Didnt think of that.....
all the 7" CWP's are interchangeable
Has anyone changed their own CWPs?
Heard the diffs are a nightmare to get apart (especially the castellated nuts either side)...
Cheers,
David
Sera
http://www.motosera.com
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mcerd1
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| posted on 25/5/09 at 07:13 AM |
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not done one myself (I got classic conversions to do mine) - but here's some bedtime reading.....
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flak monkey
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| posted on 25/5/09 at 07:53 AM |
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quote:
Originally posted by mcerd1
not done one myself (I got classic conversions to do mine) - but here's some bedtime reading.....
Forget the link?
Sera
http://www.motosera.com
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mcerd1
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| posted on 25/5/09 at 08:20 AM |
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opps
linky
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flak monkey
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| posted on 25/5/09 at 03:20 PM |
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quote:
Originally posted by mcerd1
opps
linky
You star, thanks very much
Sera
http://www.motosera.com
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mcerd1
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| posted on 25/5/09 at 03:41 PM |
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and the other link that I forgot (I must be getting old or something  )
loads of other ford manuals from the same site:
http://www.siipicossu.com/manuaaleja/manuaalit.htm
[Edited on 25/5/09 by mcerd1]
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procomp
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| posted on 26/5/09 at 07:09 AM |
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Hi
On the 750mc Kit cars with the std duratec fitted. There has been some switching between a 3.54 and a 3.7 ratio for the various circuits to get best
compromise on gearing. Obviously that's using an English axle.
Strikes me that a sierra 3.62 ratio would be right in the middle and work well with the power and torque.
Cheers Matt
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flak monkey
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| posted on 26/5/09 at 08:29 AM |
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quote:
Originally posted by procomp
Hi
On the 750mc Kit cars with the std duratec fitted. There has been some switching between a 3.54 and a 3.7 ratio for the various circuits to get best
compromise on gearing. Obviously that's using an English axle.
Strikes me that a sierra 3.62 ratio would be right in the middle and work well with the power and torque.
Cheers Matt
Hi Matt,
Thanks for that
Sera
http://www.motosera.com
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