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Diff Ratio

M

myczka68

Guest
please help. I'm running a stock blue 2.85 with an aussie 4 speed. I'm pretty sure my diff ratio is 3.08 I've been told to run 4.11 or higher. why ? my only mod at the moment is a 2 1/2 " exhaust off 2" extractors. My ride is a vh.
 

vkberlina

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your current 3.08 will give you a better top speed (ie lower rpm at say 100km) than a 4.11 however the 4.11 will give you a quicker takeoff, as the 2.85 doesnt have a great deal of torque compared to a larger capacity engine the 4.11 diff ratio could be a good thing but maybe a little too extreme (loosing too much top end)

Possibly a comprimise say around a 3.55 could give you a little more benefit. Also a 5 speed upgrade you may fine you could do a 4.11

Knock up a gear ratio chart with the different diff ratios with 2 top gear ratios for the gearbox 1:1 (aussie 4 speed) and 0.79:1 (pretty close to most 5 speeds) see what you work out could be close whilst still maintaining your top speed.
 
M

myczka68

Guest
cheers for the advice. would the top end be worth sacrificing for burn outs? woud the ratio be a simple change or do i have to consider different axles?
 

vkberlina

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Depends if you want to drive like an idiot or not. If you own a 2.85L 6cyl I dont think you need to worry about doing burnouts.
It depends on want you want to do in the car and the driving you do, if you want to try to do single wheel burn outs around corners stick the 4.11 in,

If your wanting a reasonable combination with a more spritly takeoff without sacraficing top end too much consider a 3.45 or 3.55. If you have more money to spend put in a 5 speed with a 3.45 or 3.55,even a M76 would probably hold up behind a 2.85L and would be pretty cheap. This wouldnt affect your top end at all.

Else even consider a gearbox swap to either a MC6 4 speed or M76 5 speed it will give you a better takeoff than the aussie 4 speed. NB the MC6 & M76 boxes cant handle a great deal of torque but behind a 2.85L I think you would be pretty safe.
 
M

myczka68

Guest
once again cheers. you've given me much to think about
 
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