changing rear diff

[samboatman]

Hi
I have a 325e considering changing the rear diff. What I understand, I have a 2.93 ratio. The 325i (doner car) has a has a 3.73 ratio. What would that translate in R.P.M on the highway. Right now mine turns at roughly 2100-2200 rpm @ 100km/h
thanks
Sam

[M5W]

Id say 3.73 is to high for your e. I would think a 3.25 would make a difference but a 3.45 would make your gears useless. Is the 3.73 lsd ?

[samboatman]

not sure. new to bmws. how can i tell if its lhs? I just want slightly lower gearing, I would like to tow a small alum. boat. I can buy a 325i for cheap just for parts. I was hoping to get a lhs for me...lol No more than 500 rpm higher than what im running now.
Sam

[jlevie]

If this car has a manual transmission you should be turning about 2500rpm at 70mph in 5th gear. If you switch to a 3.73 the engine will be turning about 3150rpm at 70.

[bimmer_E30]

3.25lsd + chip in an eta=tons of fun

[e30huh]

don't do it. 3.25 lsd

[long tall eta]

don't do the 3.73. find a 3.25. the 373 will be buzzing you out on the highway.

[ZM Blue Devil]

3.25lsd + chip in an eta=tons of fun

Bingo!

[MR 325]

When my Eta still had the Eta engine I had a 3.25 LSD and it was PERFECT. Towed my trailer well too.

[Rosecitykid]

I have a 3.73 LSD in my eta and I love it! It loves to roast the tires and feels so much quicker! But on the highway I'm spinning about 3,000rpms. Kinda of high but for my use totally worth it.

[r0meyrome]

Dont do 3.73 that what im running on my eta and at freeway 75mph-im at 4,200rpm...now i got a stroker 2.7 built im at 75mph at 4000rpm...

[samboatman]

Thanks for all the input guys. I'll keep my eye open for a 3:25 lsd