parkiboy
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| posted on 9/1/18 at 05:17 PM |
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Differential for my BEC
Hello, i recently bought a raw striker with a zx9r engine, this weekend i am going to start a refresh of the car as certain areas are showing signs of
age.
While i have the car stripped i am looking at changing the differential, it is currently a 3.64 7.5". I would love a 3.14/3.38 LSD but these are
near impossible to find and i wont want to go through the expense of buying a quaife for it. So i have it down to 2 options which i can get hold of, a
3.36 7.5" open diff or a 3.62 LSD 7". Which do you think would be the best option? The car will be used mainly for road use with a couple
of track days a year.
If i was to swap my 7.5" diff for a 7" would i need to purchase anything else other than the diff and driveshafts? Is everything else
compatible? (hubs etc..)
Many Thanks
Craig
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CosKev3
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| posted on 9/1/18 at 06:05 PM |
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You would Deffo need spacers to take up the extra half inch to mount it!
Some 7.5 diffs use 100 mm lobros the same as a 7 inch diff,but most likely they will be 108mm on the 7.5 but worth measuring up before you buy
more!
My R1 engine would top out in 6th gear at 121mph with a 3.62 and 15 inch wheels with 195/50 tyres.
It was revving at circa 7000 rpm cruising at 70mph,which wasn't ideal on longer journeys so I went to a 3.38.
Haven't had it flat out in 6th,but it has dropped the cruising revs to circa 6200rpm at 70 mph now which is much better 
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parkiboy
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| posted on 9/1/18 at 06:24 PM |
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thank you for your reply. I have checked the current shafts last night and they are 108mm
The main reason i am indecisive is because i would like an LSD but don't know if its worth sacrificing it for a lower ratio. I am not bothered
about top speed if i am honest but it would be nice to drop the RPM's for touring.
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martin500
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| posted on 9/1/18 at 06:33 PM |
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There is a ratio calculator on the site here: ratio calculator
This will help to decide.
I have a ZX9R Phoenix currently running a 3.38 but also have a 3.68 LSD to go in later.
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mcerd1
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| posted on 11/1/18 at 11:25 AM |
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You can swap any ratio 7.5" crown wheel and pinion set into your existing LSD that would be the most cost effective option
You just need to strip down the two diffs sway over the bits and rebuild them and adjust them and your done (a good time to fit new bearings and
seals)
All bolt-on 7" diffs have 100mm CV's so you'd have some issues with the driveshaft's and hubs if you went down this route
[Edited on 12/1/2018 by mcerd1]
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