Recommedations on differential ratios - M20 swap

[jprocket]

Well it is time to rebuild my 3.91 LSD. Any experiences on choosing ratios? My M20 is a NA 2.7 stroker with MSII and a 4 speed. Right now I pretty much top out quickly in 1st, so I'm thinking going to a 3.45 ratio. I use it as a daily drive so I want to have lower revs at highway speeds also. Near future upgrades are a 2.9 stroker kit from IE and a Getrag 260. Am I going too low using a 3.45? Maybe in between and get it rebuilt with a 3.64 ratio?

[Bobby_Digital]

What tranny do you have now? I'm running a Getrag 260 with 3.91 and my 1st gear is short too, but it cruises fine at freeway speeds in 5th gear. It takes some finesse to get going without chirping the tires, though. I'm considering running wider tires. It sounds like you might be happier with the 3.64:1 that came with most 2002's and some 320i's.

[jprocket]

I'm running a 4 speed from a 323i. Would you change to a 2.64 if you had the chance? I bet you had to do quite a bit of modifications to your tunnel to fit that 260 in there. What drive shaft did you use? I'd like to see some pics of the interior of you car. Email me off the board if you dont mind sharing some pics and information.

j24ebox at yahoo dot com

[Bobby_Digital]

Oh and I like the 3.91, I wouldn't change it given the opportunity.

[-=Charley]

1st gear is useless with my 5spd 323i tranny and 3.91 but that's OK because I dont drag race.. 5th gear taps out pretty quick though. I'd go with the 3.64 That's what the guys @ IE recommended also. It just needs a toouuch more gear and it'd be perfect for me.

[jprocket]

I will give a 3.45 a try and report back. But I am leaning towards a 3.64 - looks like it maybe a good compromise. But if 1st gear with the 3.64 is useless and a 3.45 is to low of a ratio I guess I will have to add more DISPLACEMENT to my engine so I can live with the 3.45 Decisions, decisions... Let the fun begin!

[jprocket]

I pulled the 3.91 and put in a 3.45 last night and my first impression on this mornings drive was that it seems to work better for me with the 4 speed. Maybe a little low - but maybe I'm just not used to the engine buzzing less. I think if I had a 5 speed it would be even better for highway speeds. I didnt get to cruise over 50mph for an extended time, but I was spending more time in 3rd instead of fourth while driving through town, which I like. Still is quick to me. I will drive around with this diff for about a month and then put in a 3.64. After that, I will be able to figure out what ratio I will have my LSD rebuilt to. But I have a feeling that if I do up my engine displacement to 2.9 or more - the 3.45 would be a hands down choice (especially with a 5 speed) and the 3.64 would be a good compromise if I keep the tranny and engine displacement that I have currently.