wylliezx9r
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 posted on 6/11/12 at 01:35 PM |
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Sierra Diff question - what to do ?
Right here goes; My BEC car setup is currently runnning a 3.64 LSD but i'm going to S2000 (F20C) power. The S2000 uses (i think) a 4.1 ratio
diff. With my current diff i would be looking at a theoretical top speed of over 200 mph 
Is it possible to change the ratio of my diff (cheaply) or am I better off replacing it, ideally I'm after the simplest method. I know I could
just fit a S2000 diff but that is more hassle/work than I want at the moment.
Cheers Dan
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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tilly819
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| posted on 6/11/12 at 01:47 PM |
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Got a 3.9 in mine with f20C works quite well, runs out of power about 135mph due to drag
tilly
F20C Haynes roadster 440 BHP/Tonne www.youtube.com/handmadeextreme
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Relph
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| posted on 6/11/12 at 01:49 PM |
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You could fit a 3.92 sierra diff, there fairly cheap.
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wylliezx9r
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| posted on 6/11/12 at 02:12 PM |
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Is it possible to fit the crown wheel off a 3.92 so I can keep the LSD ? I've tried researching this but I'm finding conflicting
information.
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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adithorp
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| posted on 6/11/12 at 02:23 PM |
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quote:
Originally posted by wylliezx9r
Is it possible to fit the crown wheel off a 3.92 so I can keep the LSD ? I've tried researching this but I'm finding conflicting
information.
I know people have fitted the 3.38 diff crown wheel and pinion to a 3.62LSD diff so it might well be possible with the 3.92
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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Relph
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| posted on 6/11/12 at 02:42 PM |
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Think the easyest way to do it would be to fit your LSD to the 3.92 diff then you wouldnt have to mess around changing pinion gears.
[Edited on 6/11/12 by Relph]
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wylliezx9r
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| posted on 6/11/12 at 03:15 PM |
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quote:
Originally posted by Relph
Think the easyest way to do it would be to fit your LSD to the 3.92 diff then you wouldnt have to mess around changing pinion gears.
[Edited on 6/11/12 by Relph]
Yes but what about the drive shafts ? They are bolt on, on the 3.62 LSD.
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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Relph
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| posted on 6/11/12 at 03:48 PM |
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You would swap the driveshaft flanges over aswell as the LSD, you have to fit the flanges as they push into the LSD.
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snapper
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| posted on 6/11/12 at 04:16 PM |
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2.0 DOHC 4x4 Sierra has a 3.9 LSD bolt on
I eat to survive
I drink to forget
I breath to pi55 my ex wife off (and now my ex partner)
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Simon
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| posted on 6/11/12 at 05:24 PM |
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Can't see the point in changing meself. Car is substantially lighter than S2000 and engine more torquey than bec so should think it'll be
fine with current one. Top speed is only theoretical and utterly irrelevant
Try it first as is, as it'll only be a couple of hours to change at most if you don't like it
ATB
Simon
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CNHSS1
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| posted on 6/11/12 at 07:36 PM |
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Its likely the overall rolling radius of the tyres fitted to a 7 type will be smaller than an S2000, so the diff final drive will be pretty good imho.
You can fit any CWP set from another similar sized sierra diff, ie 7" to 7" or 7.5" to 7.5"
Use the gearboxman gear calculator, it has a rolling radius value to allow for tyre wheel combo chnages
"Racing is life, everything else, before or after, is just waiting"---Steve McQueen
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wylliezx9r
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| posted on 6/11/12 at 09:07 PM |
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quote:
Originally posted by Simon
Can't see the point in changing meself. Car is substantially lighter than S2000 and engine more torquey than bec so should think it'll be
fine with current one. Top speed is only theoretical and utterly irrelevant
Try it first as is, as it'll only be a couple of hours to change at most if you don't like it
ATB
Simon
Yeh I'm with you about the topspeed , but I just think that the 1st four gears should be within a useable speed band especially since its a high
revving engine.
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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wylliezx9r
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| posted on 6/11/12 at 09:10 PM |
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quote:
Originally posted by CNHSS1
Its likely the overall rolling radius of the tyres fitted to a 7 type will be smaller than an S2000, so the diff final drive will be pretty good imho.
You can fit any CWP set from another similar sized sierra diff, ie 7" to 7" or 7.5" to 7.5"
Use the gearboxman gear calculator, it has a rolling radius value to allow for tyre wheel combo chnages
Is that definitely true about the interchangeability?I thought the cwp's can have different lengths ?
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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CNHSS1
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| posted on 6/11/12 at 09:47 PM |
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I have only swapped 3.62 & 3.9 7" personally, but i know a mates swapped 3.62 7" to 3.14 CWP
Maybe ask on passionford if you want more info, those boys seem elbow deep in diffs daily!
"Racing is life, everything else, before or after, is just waiting"---Steve McQueen
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Simon
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| posted on 7/11/12 at 12:58 AM |
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quote:
Originally posted by wylliezx9r
Yeh I'm with you about the topspeed , but I just think that the 1st four gears should be within a useable speed band especially since its a high
revving engine.
Ok, so instead of using 4th, use 3rd etc.
I did a spreadsheet ages ago with calcs for 3.92/3.62 and 2.88 (Jag irs) which will show you the differences it'll make - I was going to put a
2.28 bmw diff in mine but sold car instead, see
[img]
 
speed in gear - various f/d ra
[/img]
Going from 3.62 to 3.92 will be so insignificant as to be pointless. Still, your money/time and choice
ATB
Simon
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wylliezx9r
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| posted on 7/11/12 at 10:07 AM |
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quote:
Originally posted by Simon
quote:
Originally posted by wylliezx9r
Yeh I'm with you about the topspeed , but I just think that the 1st four gears should be within a useable speed band especially since its a high
revving engine.
Ok, so instead of using 4th, use 3rd etc.
I did a spreadsheet ages ago with calcs for 3.92/3.62 and 2.88 (Jag irs) which will show you the differences it'll make - I was going to put a
2.28 bmw diff in mine but sold car instead, see
[img]
speed in gear - various f/d ra
[/img]
Going from 3.62 to 3.92 will be so insignificant as to be pointless. Still, your money/time and choice
ATB
Simon
I'm just going to give it a go as it is ,If it dosent work for me I'll change it at a later date.
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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mcerd1
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| posted on 7/11/12 at 10:08 AM |
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quote:
Originally posted by wylliezx9r
Is that definitely true about the interchangeability?I thought the cwp's can have different lengths ?
yes - you can swap any 7"
CW&P set for any other 7" one
(and any 7.5" for any other 7.5" too)
I've got a 7" 3.92 LSD for mine (built for me by stuart at classic conversions), but as snapper says these are standard in 2.0
XR4x4's
all ford LSD's have to use bolt-on shafts, but the open diffs can have either type (LSD's use unequal length stubs, open diffs use equal
lenght ones)
I've got copies of fords diff re-build manual and I might even have a spare 3.92 CW&P set kicking about too (I'll check my spares
later if needed)
[Edited on 7/11/2012 by mcerd1]
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wylliezx9r
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| posted on 7/11/12 at 01:13 PM |
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quote:
Originally posted by mcerd1
quote:
Originally posted by wylliezx9r
Is that definitely true about the interchangeability?I thought the cwp's can have different lengths ?
yes - you can swap any 7"
CW&P set for any other 7" one
(and any 7.5" for any other 7.5" too)
I've got a 7" 3.92 LSD for mine (built for me by stuart at classic conversions), but as snapper says these are standard in 2.0
XR4x4's
all ford LSD's have to use bolt-on shafts, but the open diffs can have either type (LSD's use unequal length stubs, open diffs use equal
lenght ones)
I've got copies of fords diff re-build manual and I might even have a spare 3.92 CW&P set kicking about too (I'll check my spares
later if needed)
[Edited on 7/11/2012 by mcerd1]
That would be great if you could, thanks very much !
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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