Dale
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| posted on 18/1/06 at 02:35 PM |
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Rear end gearing.
Getting close to putting the limited slip into my rear axle. Ford 7.5 inch North american alxe. Just wondering on which rear gears would work well.
I am probably looking at 700 kg for the car when finished and a minimum of 225 rwbh and at least that much torque. The gears I have already are
3.08s and that will put me just about to shift to 3rd gear at 60mph. Does it seam to be roughly in the right area or is the gear range too long.
Dale
Thanks
Dale
my 14 and11 year old boys 22
and 19 now want to drive but have to be 25 before insurance will allow. Finally on the road
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JoelP
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| posted on 18/1/06 at 02:40 PM |
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seems odd, those figures. What engine/box and tyres/wheels are you using?
I would've expected a 3.08 diff to give you a very high top speed, but if you are into 3rd by 60 then im guessing something around 100+ ish flat
out? Probably adequate, but 3.08 is low. Imagine how slow it would be with a 3.9 diff.
I assume by a 7.5inch ford diff you mean the diff fitted to cosworth sierras/merkur? And granadas etc.
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froggy
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| posted on 18/1/06 at 04:51 PM |
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id stick with the 3.08 as you have a torque multiplier bolted to the side of engine. if you run 15"wheels and 50series tyres the gearing will be
the same as the 2.8 5 speed capri which iirc would be 2750rpm at 70mph in top hth
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Dale
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| posted on 18/1/06 at 05:08 PM |
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Sorry I did not give enough info. The engine is a 2.3 ford turbo with a t5 from a thunderbird. and thunderbird rear axle.
From gear calc
Gear Mph per 1000 RPM Mph @5800 RPM Mph @6500 RPM
--------------------------------------------------------
1 5.93 34 39
2 10.08 58 66
3 16.04 93 104
4 23.90 139 155
5 29.50 171 192
Mph RPM (in Gears)
The car that this came out of was a 13 sec 1/4 miler with a 300lb driver- even I am lighter than that. The car was around 3000 lbs.
Dale
Thanks
Dale
my 14 and11 year old boys 22
and 19 now want to drive but have to be 25 before insurance will allow. Finally on the road
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JoelP
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| posted on 18/1/06 at 06:23 PM |
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192mph!
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ned
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| posted on 18/1/06 at 06:25 PM |
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imho i'd gear the car for around 130mph, your current gearing from the above info shows max revs in top gear @ 192mph?! it's never going
to pull that and all you'll be doing is compromising acceleration through the gears. a 3.62 or 3.92 if available over there would be better
ratios imho.
Ned.
beware, I've got yellow skin
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Dale
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| posted on 18/1/06 at 06:51 PM |
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I dont think it will ever pull those speeds - certainly not with me in thats for sure. I am not going to be doing any racing except maybe a few
trips to the strip to get some certified results.
If I go to the 3.9 or 4.11 I dont think I will ever keep traction. It would probably pull harder in the higher gears though. I may have to look
around for a set of 3.27 or 3.62 or so. The 3.08 puts me at good rpms for cruising but I guess it will all come down to where my power hits in the
rpm range. I should be able to have full boost by just under 3000rpm.
Thanks
again
Dale
Thanks
Dale
my 14 and11 year old boys 22
and 19 now want to drive but have to be 25 before insurance will allow. Finally on the road
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JoelP
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| posted on 18/1/06 at 06:57 PM |
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if i were you, id try it with the 3.08, but id really expect it to be more fun with whatever ratio is closest to 3.5. Do you have to select one now to
put the LSD in, or could you test it first with a few different gears?
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Dale
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| posted on 18/1/06 at 07:15 PM |
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Pretty sure the lsd is independant as to the gearing.
Dale
Thanks
Dale
my 14 and11 year old boys 22
and 19 now want to drive but have to be 25 before insurance will allow. Finally on the road
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mark chandler
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| posted on 18/1/06 at 09:36 PM |
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In the 'old days' you geared a car so that straight through the box at max rpm = the top speed that you wanted, 5th then becomes an
overdrive.
For outright performance 5th at max rpm is the fastest part of the circuit with the torque curve falling in line through the cogs... ie when you
change up approaching max revs the torque in the next gear gave you better acceleration than hanging on to the cog.
I,d say 139mph @ 5800 rpm in 4th would not be far out (maybe a little high) given that your engine should have a huge torque spread with the turbo and
its for driving not racing.
Regards Mark
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Mark Allanson
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| posted on 18/1/06 at 09:50 PM |
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As you have a 5 speed box, make use of it, if you gear too low, first is a total waste of time. I think is is best to have fifth as a cruising gear,
2500rpm at your ideal motorway speed. Most of my accellerating is done between 30 and 90 so 2 gears covering this range is ideal IMHO
If you can keep you head, whilst all others around you are losing theirs, you are not fully aware of the situation
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snapper
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| posted on 18/1/06 at 10:06 PM |
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Have a look at the diff calculation program here, or Google Bowling and Grippo if i dont get the link to
work.Bowling and Grippo
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