carnut
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 posted on 28/12/03 at 05:24 PM |
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diferential ratios
Hi All,
Ive got a ready to sva indybird but with the diff i have in, it will hit the limiter in 6th at 93mph. I think this is very poor cos not only do i
want to go faster but it will be difficult to cruise at say 60.
Im currently using a sierra diff (ratio 3.9 i think) but it is the wider diff(0.5 inchs wider across the top mount.
Does anyone know what is the tallest ratio i can get in the same size of diff, preferably limited slip.
thanks
carnut
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alister667
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| posted on 28/12/03 at 05:36 PM |
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Where did the original diff come from? Is it an LSD? I know the XR4x4 (rear) diff was LSD, and was *usually* 3.62. I have a 3.62 Sierra open diff
going from a fireblade onto high profile 15" tires (not on the road yet). I know the open diff size I have comes in 3.11, 3.36, 3.38, 3.62 and
3.9 ratios. I can measure the width of the top hangar of the diff if you want.
I bet your car would be hard to beat to 60!
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alister667
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| posted on 28/12/03 at 05:46 PM |
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Also I've uploaded Speedcalc.xls it's a spreadsheet (works in Excel) that
enables you to type in diff ratio, tire size and engine type to see the max speeds in various gears, should help you to see what you have to do to get
a decent cruising speed. Mind you I've noticed it doesn't have the blackbird engine on it. BTW I didn't write this, but props to
whoever did, it helped me a load.
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cosworth
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| posted on 28/12/03 at 07:08 PM |
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If its a 7.5" diff with a 3.9 ratio then its from a Granada. You can get 3.64:1 diffs either from some of the larger engined scorpios or from a
2WD Sierra Cosworth, however they are likeely to have larger output flanges to take 4.5" lobro joints with M10 bolts as opposed to the 4"
lobros with M8 bolts on your diff. You could always fit a 7" diff with spacers between the diff and the chassis. You can get a 3.62:1 7"
diff from any of the 4WD Sierras
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bike_power
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| posted on 28/12/03 at 09:23 PM |
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You'd probably find a 7" 3.38 would be better, these are on the older 2.0 Sierra and some of the economy models. I think the early
V6's also had this ratio.
The benefit of the 7" diff is that the driveshafts are a lot lighter, the difference is quite significant. The diffs are also a lot lighter
too. My 7" with a ZF LSD is lighter than an open 7.5" diff.
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carnut
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| posted on 29/12/03 at 09:47 AM |
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thanks for the input guys. The diff i have is no LSD and is from a 2.0 sierra saphire and i believe is the same one fitted to a granada.
bike_power: do you know where i can get a 7" diff with zf lsd. Also does this diff have the same size of flange on its outputs as the
7.5" i have.
cheers
carnut
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