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Guest Message by DevFuse

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4.1 ratio diff matched with 4.11 ratio...

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4 replies to this topic

#1 el_freddo


    Eat, Live, Breath Subaru

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Posted 26 December 2012 - 08:59 AM

G'day - this could be a stupid question from a crazy Aussie, but here goes anyway:

If I was going to drop a 4.10:1 ratio rear diff into my subi with a 4.111:1 front ratio what would be the consequences of this on the viscous centre diff?

Got an idea in my head that I want to do on the cheap if possible - I really don't want to buy a new R&P set if possible, but I also really don't want to destroy my centre diff.

I know the ratios are close, but are they close enough not to do damage?



#2 1 Lucky Texan

1 Lucky Texan

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Posted 26 December 2012 - 12:08 PM

I have no experience but, when these type issues come up, I often wonder if there's a way to compensate with different tire sizes on front vs rear axle.

maybe not practical for many people but, just a mental exercise hah!

#3 Gloyale


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Posted 26 December 2012 - 01:49 PM

Not sure about damaging anything.

With that setup you'd have a slight rear power bias......might be good for drifting:brow:

Perhaps run some slightly worn down tires on the back, and brand new up front?

#4 presslab


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Posted 26 December 2012 - 02:07 PM

Subaru once specified a maximum difference of 1/4" in tire rolling circumference. Although they also supplied a doughnut spare that violates that.

Anyway the difference of 4.1 and 4.111 is 0.27%. 1/4" on a 205/50-15 tire for example is 0.35%. I think you will be just fine, just be sure to rotate the tires as scheduled.

#5 el_freddo


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Posted 28 December 2012 - 05:33 AM

Ok, I'm not keen on running the different ratios, even if it is a tiny bit out. Through some other questions else where on the web I've found that I can get the 4.111:1 at a reasonable price - last time I checked it was two or three times the current amount.

Plan is to fit another vehicle's diff to the rear of my subi and run an air locker - this way I can still safely use my AWD in the snow/really slippery conditions without the rear end sliding out as it would with a welded or auto locker.



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