time to start a huge build (well huge to me)

[shiftbmw]

If all else is equal, go with the 4.10. I'd prioritize a working, good shape diff first, LSD second, and ratio third.

WIth the 4.10 versus the 3.73, your rpms will be roughly 10% higher at any given time than they would be at the same gear/speed with the 3.73.

There will be an effect on your fuel mileage and more wear on your motor/tranny but both will be pretty much inconsequencial. You are maybe talking a 2 mpg loss...your mileage is a lot more dependent on your driving habits.

Like Blunt mentioned though, don't get too hung up on the diff ratio choice. Both are pretty ideally suited for an M20/getrag 260. There are other places to spend money first in terms of fun per dollar ratio.

[Philo]

Every m20 car I've come across had either LSD or came with LSD and had burnt clutches. Guess it was a coincidence?

How ironic. I have no clue how that would happen. . . . :blowup:

I have a Metric Mechanic M20 and 3.73 LSD. So I cruise 70 @ just under 3k and shift into 4th at about 90, and thats with redline @6500 :D

So it depends on what you are running.

[rThor432]

What is still incorrect? I'd like to know so I can know better next time and so I can fix my mistake.

In that case, you don't want the 87 because its an eta and the 91 is more powerful.

'87 could be all sorts of things, but for the US market it is either an eta or "i", not necessarily either. B25 is a B25, so no real difference from the '91.

I might be nit-picking, but that was the only problem I noticed with your post earlier before you edited it.

[rThor432]

So I cruise 70 @ just under 3k and shift into 3rd at about 90

You shift into 3rd at 90 with a 3.73?

[nando]

You shift into 3rd at 90 with a 3.73?

I think he means shift into 4th at 90. I do that with a 4.10 :p

[Kerrath]

'87 could be all sorts of things, but for the US market it is either an eta or "i", not necessarily either. B25 is a B25, so no real difference from the '91.

I might be nit-picking, but that was the only problem I noticed with your post earlier before you edited it.

All fixed now. Thanks for informing me.

[Philo]

I think he means shift into 4th at 90. I do that with a 4.10 :p

Correct.

by keypad. What a sad day. Stupid Iphone.

Time for fixie.

Oh and I have yet to try it with the redline at 7200. I can hear fun calling my name.

[Rockinlittle325i]

Off topic........ OP are you in North Carolina?

Back on topic. Blunt's first post was right, too much mis-information in those first 5 posts.

ya man, I'm right beside carowinds, what about yourself?

[Rockinlittle325i]

well I know a fello in my area that had a 4.10 and he said it made it like night to day in his car, that and a chip

and of course I'm going to make sure the diff is in good working order before I use it,
both choices are LSD

[rThor432]

I'm in the Mt. Island area, on the border of Huntersville/Denver. Always good to know more local guys.

Really, as far as the diff goes either will be good for you. I like the 3.73 for the mildly better highway driving. But that's because all of my street driving is highway cruising on I-485.

On the track, I've known several people who have run the 4.10 for a couple of seasons and then switched back to the 3.73. They say that initially the acceleration is better, but then they start to feel like they are shifting a bit much. Something like that.

[Julien]

to the OP, make sure what you are getting into, very easy to get nickled and dimed in an operation like this... make sure everything is complete and that he has spares also... About the diffs, take which ever is a big case lsd, if both are go for the 4,10

[Rockinlittle325i]

to the OP, make sure what you are getting into, very easy to get nickled and dimed in an operation like this... make sure everything is complete and that he has spares also... About the diffs, take which ever is a big case lsd, if both are go for the 4,10

will do, I plan on making an agreement with him to where I dont have to spend anything,
you know to make it an even swap

[Rockinlittle325i]

I'm in the Mt. Island area, on the border of Huntersville/Denver. Always good to know more local guys.

Really, as far as the diff goes either will be good for you. I like the 3.73 for the mildly better highway driving. But that's because all of my street driving is highway cruising on I-485.

On the track, I've known several people who have run the 4.10 for a couple of seasons and then switched back to the 3.73. They say that initially the acceleration is better, but then they start to feel like they are shifting a bit much. Something like that.

hey lets see if we cant have a big meet somewhere with all the local e30 guys

right now I dont know, a few people have told me different stories, they either love it or utterly hate it,

[rThor432]

hey lets see if we cant have a big meet somewhere with all the local e30 guys

right now I dont know, a few people have told me different stories, they either love it or utterly hate it,

I work too much to get out to the local meets. I'm too tired and fall asleep driving if I go out late. The next big event I'll be at will be Vintage at the Vineyards. Any guy in NC or the surrounding areas that has a car that can make it will/should be there. That's a nice event for meeting new people.

And for what it's worth, owning so many etas spoiled me. I've got a 2.93 in my car now and it pulls great. My 318is, 323i, and 325i all had gearing that bugged me a bit (mostly just the revs on the highway, they were buzzy.. Just the way I am though.

[Rockinlittle325i]

OK guys I have big news,
I went by the shop today and the e30 in question is a 318is, with a 4.1 lsd
I'll have pictures soon,
My main question is what do I need to look out for when I drop a M20 motor in it?