givemethebighammer
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| posted on 20/2/06 at 09:11 PM |
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4.4 ratio diff, should I
I have been offered 4.4 crown and pinion wheels to fit my 7" 3.62 LSD. I had already decided to put the 3.92 crown and pinion into my diff to
make the car livelier to drive (at the expense of reduced top speed).
I have been messing with gearcalc, a 4.4 diff with a standard sierra gearbox and 185\60\14 wheels\tyres. Looks to make the gearbox very useable.
(except the very short first)
What do you think 3.92 or 4.4 ?
ps
2.0L zetec, 6000 rpm peak BHP, 7200 rpm rev limit.
[Edited on 20/2/06 by givemethebighammer]
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givemethebighammer
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| posted on 20/2/06 at 09:12 PM |
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and the capri one.....
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ned
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| posted on 21/2/06 at 08:09 AM |
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i'm putting a 3.92 in my 2.0 xe powered car, peak power around 6500rpm i expect and 7750 rev limit..
1st gear will be useless anyway. 3.62 is ideal for 0-60 in one gear, buti decided i'd probably not use the top end much.
Ned.
beware, I've got yellow skin
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bimbleuk
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| posted on 21/2/06 at 08:48 AM |
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I've got a 4.44:1 crown wheel in my Striker diff.
1600cc 4AGE 20V - 147BHP @7800 - limit set to 8200 RPM.
However I've also got a BGH gearbox with much taller 1st and 2nd gears to make them useable. I can do 0-60secs using only 1st and 2nd due to my
engine being able to rev so much!
I would have doubts about using the 4.4:1 without changing the ratios of 1st and 2nd. Also remember your cruising RPM will be quite high with that
diff ratio installed. If you pimarily use it on the road then the 3.92:1 ratio is much easier to live with.
[Edited on 21/2/06 by bimbleuk]
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NS Dev
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| posted on 21/2/06 at 09:25 AM |
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I used a 4.6:1 diff in my RWD Pug rally car, with a std type 9 gearbox.
1st gear is for maneuvering only, and 2nd to 5th is a 4 speed, but top end gearing is about right with 7500rpm limit. Top speed 115-120mph at full
revs.
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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givemethebighammer
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| posted on 21/2/06 at 08:17 PM |
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I have been talking to BGH about converting a 2.8i capri gearbox I have to what they call a 2.8i sporting close
1st - 2.66
2nd - 1.75
3rd - 1.26
4th - 1.0
5th - 0.825 / 0.84 / 0.86 / 0.89
Just musing over the 5th gear ratio
0.825 gives 134mph at the rev limit 7200 (about 110mph at peak bhp - 6000rpm)
0.89 gives 124mph at the rev limit 7200 (about 105mph at peak bhp - 6000rpm), but will probably pull much better.
Whatever I do cruising at 70-80mph will be at 3700 - 4600rpm (not too bad)
the rpm drops when changing at 6000rpm also put the car right where it comes "on cam" too.
On paper it all looks like a good move, but will it be a pain to drive on the road ?
However the cars a weekend blaster and trackday tool so maybe ?
decisions........
[Edited on 21/2/06 by givemethebighammer]
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ned
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| posted on 21/2/06 at 09:30 PM |
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for info the quaife/tranx conversions offer 0.87 or 0.9 iirc, the 0.86 would likely be my choice from the options available to you...
Ned.
beware, I've got yellow skin
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givemethebighammer
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| posted on 21/2/06 at 10:29 PM |
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I've been messing with the quaife calculator. Here's the plots for 3.62, 3.92 and 4.4 diff with the above ratios (0.825 5th). I think you
may be right Ned the 0.86 does (on paper) seem to be the one to go for.
[Edited on 21/2/06 by givemethebighammer]
 
Rescued attachment calc.JPG
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