What's your final gear ratio?

[xLibelle]

For autocorss and track... or anything really.

Looking for feedback on your setup and how it works for you.


I have a 4.10:1 behind a stock m20 w/ manual so my gears are short, as expected. Its intersting to blast through the gears on street but i'm always hitting the revlimiter at autocrosses as 2nd gear is really played hard near the top end of the spectrum.

My other note worthy vehicle was an eta with supercharged m20 transplanted into it. With the added power, the 2.93 is appropriate. Would be a bad thing to have with less power, especially at an autocross me thinks.

[xLibelle]

bump

[iwillhunt]

I have a 3.25lsd in my eta.

But I'm guessing the m20 your referring to is an "i" motor, so i'd think a 3.73 may be a good improvement without being too tall.

[JGood]

3.73 in the 325is, 3.25 in the eta. I think they are both about perfect, but I don't go over ~70 on the highway, so if you are the type of person that needs to do 85-90 to get to your destination 3 minutes sooner, you may not like the 3.25 in the eta.

[DSP74]

I've got a 4.10 lsd from an auto is. And that's what I'm going to stick with for now.....I may swap valve springs and search for new rockers. And rev to 7K. And tire size plays a HUGE roll too. I'm planning on running a 25.5" tall rear tire.

[PiercedE30]

I've got a 4.10 LSD, like DSP. Cruising at 80 my RPM's are at about 3700-3800. My rev limiter is set for 7200. I also don't have to worry about breaking rocker arms though.

[rwh11385]

3.73. I had a 4.10. Top of 2nd is more useful for autocross. I can carry more speed in 3rd at the track with the 3.73. Of course, most of the turns I now carry in 4th even with the 3.73...

but don't upgrade your diff unless you swap i'd say. not a huge difference. not that i won't reinstall my 4.10 after the bearing is replaced, but it's not worth the $$ I paid...

[bam2002]

I would say on an engine that can rev to 6 or 7 K a 4:10 would be OK for an Autocross. But it be way to high for a track day.
A 3:25 to 3:75 would be better for a track, So if your looking for an All in one Diff.. then the 3:7x would be best.

[E30_fiend]

3.73 seems to be the right diff for a lot of applications. Its like the perfect ratio. Not too tall not to short and its still lsd.


E30Fiend

[Gleb]

Just ordered a ZF S5-31 tranny, new driveshaft, 3:46 4-disk diff and an M5 clutch+LTW flywheel from Metric Mechanic:D
Turning my E30 into a race car, will let you know how it goes with the diff.

[nando]

4.10s with a 7k redline - on some of the power courses I'm on the redline a lot, but for many of the more technical ones it's perfect. I would like to raise the redline another 200rpm or so, and I know the engine could take it, but my cam is way past it's peak range by that point. I data logged my last autox, and beating the shit out of the redline I hit 7150rpm along the way - worked out to be around 58mph.

[gearheadE30]

I need the 4.10, but I have an M42. For you (and all of the other M20's I've driven) the 4.10 is too short. That motor just doesn't like to rev as much as the M42, and it isn't as happy or efficient doing so. I'd go 3.73 or 3.91 if you can find one.

[e30polak]

I went from a 4.10 to a 3.25 in my car and it's a catch 22. I miss the torque in 2nd-4th, but 1st gear was useless. With the e36 tranny and the 4.10 I redlined 1st at like 22 mph at 7300K. Anyway the 3.25 is nice round town, 3rd and 4th are super long, but i want more torque down low before vanos really hits. I'm either goin to switch to 3.46 or 3.73 to get more torque back without having to shorten the gears too much.

[Mulholland]

By the math.. with a 2.92

1st. 34
2nd. 60
3rd. 94
4th. 131
5th. 162

^^^stock eta with a 5400rpm redline... I am looking for a 3.25LSD locally, which should make the car considerably faster up top I think. I pretty much top out drag limited in 4th right before redline, only grabbing 5th on a top speed run for an extra bit of umph to top out. The chip makes a world of a difference, but it also makes the 2.93 feel even more docile.

[rsafier]

On a M20 AutoX car depends on the course. If your running smaller local events with tight and fairly compact lots then a 4.10 probably will work better as you won't need to worry about running out of 2nd gear often. Larger courses and anything at more then local level generally are much more open (faster) so a 3.73 works better, or a legal swap of a 3.64 (I think from the iX but you change to the clutch pack LSD) might be better option.

As for FI cars if you have street tires 2.93 seems the way to go you need to limit torque. I found with enough grip tho it can be hard not to bog. on my 285 r-comps I'm running a 3.25, works pretty good tho still can bog. a 3.46 might be a good option but could make 1st even more useless and 2nd harder too hook up when your in the 300+rwhp range. The advantage would be quicker back into the boost off slow corners. Plus depending on the track you might run out of 2nd. I find most of the time I just kiss the rev limit (I use 6500rpm) on most courses that are larger. Only have been to one site that was setup in a way that required 3rd gear.
Main factors are your power level, and the courses you run, pick a gear that will keep you in a good power range coming off of corners.