Gear ratio opinions

[Ding250SX]

Hey guys been a lurker here for a while but I've come out of the shadows. i have a 1990 325i with a 4.10. Open diff rear end (car used to be auto). It's pretty fun just banging out gears but driving on the highway it's pretty unbearable crusing at 3500 rpm. I just got a 3.25 LSD for FREE from a coworker. I've looked at the ratio calculator and this gearing seems pretty long for the g260 trans. Does anybody have any feedback on this setup? I know a lot of the ETA guys like them but i want to know how the late model guys feel about the 3.25 ratio.

[ELVA164]

It's really too tall. 3.73 or possibly 3.64 are the best all-round ratios for a stock 2.5. You could probably sell or trade that pretty easily for a 3.73LSD which would work great.

[Ding250SX]

Yea that's what i figured. 5th gear will be way too long with the 3.25 ratio. That being said, 1st gear is pretty useless with that 4.10 ratio. I'll probably install it this weekend anyway just to make sure it works good and is quiet.

[ELVA164]

I've always wondered what it would be like to have a 3.25 and one of the close-ratio dogleg gearboxes...lemme know what fourth gear is like with the 3.25 installed if you would.

[Poopie]

I would trade you my 3.73 LSD. It's not happy on the highway with my zf trans

[jeffnhiscars]

Now that I've done my 5apd swap I'm not thrilled with my 3.73 open and am coveting the 3.46 torsen that's sitting in my ETA :)

[flyboyx]

I don't know where you would find a 3.64. Early euro ix is the only vehicle that I know of that came with this ratio. 3.46 would be easier. 633csi could have come with this ratio.

You can run the 3.25 and it will be fine for the highway, but your car won't have a lot of pep around town. I presently have a 2.93 in my mtech 2. It was fine here in Houston, but the only races I would win are probably against priuses and yugos. Unfortunately, the car has been in Denver for the last year and a half. I didn't consider what effect that tall ratio would have combined with 6000' of altitude. I will say my decision to use this ratio here was a bad one. It really sucks in the mountains. I've actually had situations around 9000 feet where the car was literally incapable of moving forward from a complete stop on a fairly steep hill. I had to either back up and get a running start or give up and go another way.

On the plus side, when I switched from 4:10 to 2.93, my economy went from about 20 or less to about 25 or 26.

[TobyB]

Oh, those are easy- any early 318 with a manual had a 3.64. Of course, it's small case, so get the flanges, too.
And it might not last all that long- if you track it.

heh

t

[packratbimmer]

I run the 3.64 small case. They wear out faster so you get some noise, but I am pleased with the ratio. I would not go taller than 3.45 or 3.46. I had a built 3.23 in my 89 325i. It was great on the highway for comfort (got the revs down), but economy was not improved and it felt wrong everywhere else.

[jeffnhiscars]

This may help. I installed a 3.46 torsen in the ETA which comes from a 00-02 Z3 3.0 auto trans car.