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From digest.v7.n1198 Thu Feb 26 14:27:59 1998
From: "T VanAusdal" <>
Date: Thu, 26 Feb 1998 07:30:01 PST
Subject: Re: rear end -eta

>Sorry if this hits twice, this is my first time sending sending to the
>I have recently entered the 80's and purchased a 1987 E-30 (325e) to
>replace my 1976 2002. I am in the process of adding a few upgrades
>including an "i" cam, k&n, ansa and chip. The question I have relates
>the diff.

Since you're going with an 'i' cam, you'll have a 6K rpm motor, right? The 325i is a 6K+ motor, runs a 3.73:1 gear just fine. Coming from a 2.91 ratio to a 3.25 is a nice step up for you.

Two points to consider: the 3.73 gear in 5th is pretty close to 4th gear in the 2.91. (It's like a 3.02 ratio Drive around without using top gear a day and see if you can stand that.

OTOH, you have an 'i' cam in an 'e' head (assuming non-super-eta), which means it peaks at slightly lower revs than a 'true' 'i'. [Larger ports in the 'i' head make peak flow occur at higher rpms, equals peak torque at higher rpms than the 'e' head.]

So the 3.73 is not as necessary (a 3.64 or 3.45 would be good). How not as necessary is up to you. 3.25= good compromise.

  • thi v.

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