english diff rebuild

[Fizzer]

Hiya, has anyone used these people before?
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=280611025918&fromMakeTrack=true&ssPageName=VIP:watchlink:top:en
I'm thinking of getting a quaife atb lsd but do not want to learn how to set a diff up properly.

Question two: I fitted a 3.54 diff last winter to get the revs down for our round trip of France. Worked perfectly. I still have the old 3.89 diff and am intending to do a few track days this year. Would you fit the LSD to the 3.89 or the 3.54? Purely subjective question of course! I have a fury with 2.0 blacktop + type9 and 13" capri laser wheels. Would I run out of revs on track with the 3.89?

[MattD]

Assuming 185x60 x 13" tyres, STD Sierra Type 9 gearing, and presuming you have enough BHP to overcome the aero drag and can the achieve the MPH figures:-

shift point: 7200 RPM
rev drop speed MPH
1st to 2nd 3314 36
2nd to 3rd 2193 67
3rd to 4th 1945 96
4th to 5th 936 132
5th top speed 151
Final: 3.54 :1

shift point: 7200 RPM
rev drop speed MPH
1st to 2nd 3314 33
2nd to 3rd 2193 61
3rd to 4th 1945 87
4th to 5th 936 120
5th top speed 138
Final: 3.89 :1

with the 3.54 that's 130mph your doing when you shift from 4th to 5th at max revs (unlikely to get anywhere near that with a stock blacktop)
with the 3.89 its 120mph at the same gear same revs, which is much more acheivable.
Either way you're using it as a 4 speed box at most circuits, 5th only on the "really" fast bits or if you're being mechanically sympathetic.

Based on that I'd fit the LSD to whichever diff I was going to use on the track - for me it has to be the 3.89.

[petercoll]

^

What Matt said.

Pete

[Fizzer]

Thanks for the advice guys, I think you're right, even though it's a long way from a stock blacktop (177hp @7,200)
It sound like I won't run out of revs with the 3.89