swapped cars and diff ratios

[BustaRhymes325i]

I'm running an s50, a 2.93 lsd, and some sort of e36 trans, but I feel like in 5th gear I am still turning too many rpms at cruising speeds. Is the m20 tranny better, and what considerations should I make if going FI and wanting to make around 400 hp?

[phreshkid]

huh

[kalib0y]

what RPM is your 80mph at?

I also have an s50 and I had a 2.93. I love it on the hwy and longer gears, but until I supercharge my e30, I swapped in a 3.25 for now. Oh and I have a ZF tranny

[nrubenstein]

Depending on what you're after, the G260 is geared around 80% of the G250/ZF320. It'll drop your RPMs.

[BustaRhymes325i]

Ill go make a run tonight and record milestones so you guys can help me. I wanna say at 65 I may have been around or just under 3k.

[Adrian_Visser]

I really don't get why people are always wondering what their cars will feel like with the stock diff and stock trans. I mean an m/s50 has the same rev range as an m20, you are going to be turning the same rpms at speed as before.

[87e30]

Just to clarify the e30 g260 is geared shorter than the zf e36 trans, right?

[green]

For some reason, I thought the ZF had shorter gearing than the 260. I know that the ZF has a 1:1 5th gear whereas the 260 has a .81 5th gear.

[nrubenstein]

Just to clarify the e30 g260 is geared shorter than the zf e36 trans, right?

Wrong.

Also, you guys know that you can calculate what revs you're going to hit with a given trans/diff quite easily, right? I mean, the math is pretty simple, but there are plenty of gear speed calculators out there, too. Just input the ratios and see.

[87e30]

Wrong.

Also, you guys know that you can calculate what revs you're going to hit with a given trans/diff quite easily, right? I mean, the math is pretty simple, but there are plenty of gear speed calculators out there, too. Just input the ratios and see.

Okay, I misread the above comment. Thanks!

[Wh33lhop]

Just to clarify the e30 g260 is geared shorter than the zf e36 trans, right?

The transmission itself, no--the opposite. Gear spacing 2-5 is very similar between the two transmissions with first gear being about ten percent longer in the ZF though. So, a 2.93 with a ZF is very similar to a G260 with a 3.73 with the exception of a slightly longer first gear.

For some reason, I thought the ZF had shorter gearing than the 260. I know that the ZF has a 1:1 5th gear whereas the 260 has a .81 5th gear.

Technically it has shorter gearing, but you need a final drive before that gearing hits the wheels. Your final drive (diff ratio) will determine how short your gearing is overall.

However, if the same final drive is used between the ZF and the G260 then yes, the ZF will have significantly shorter gearing by about 20% overall.

[etxxz]

I'm running an s50, a 2.93 lsd, and some sort of e36 trans, but I feel like in 5th gear I am still turning too many rpms at cruising speeds. Is the m20 tranny better, and what considerations should I make if going FI and wanting to make around 400 hp?

the m20 tranny (ie: G260) has longer gears than the e36 tranny (ie: ZF).
The 2.93 is already the longer diff that you can run in an e30, 4.10 being the shortest... short of some after market racing gearing.

G260 Gear Ratio:
1st 3.83:1
2nt 2.20:1
3rd 1.40:1
4th 1 0:1
5th .81:1

ZF Gear Ratio
1st 4.20:1
2nd 2.49:1
3rd 1.66:1
4th 1.24:1
5th 1.00:1

e30 gear ratios avail
2.93, 3.25, 3.64, 3.73, 4.10

to the left gears get longer, to the right, gears get shorter.
This is to clarify all doubts on this thread, numerically.

To answer the OP's question - so what if it revs, let it turn! its a sports car. That's a good gearing for a boosted car. How you're gonna get accomplish 400hp, is another story. Good luck with your project, Its a r3v policy to document your work.

[StereoInstaller1]

I used the calculators at http://www.rocky-road.com/calculator.html to figure this out:

---All of the below are at 2500 RPM----

215/40/17 (23.77") with a 3.73 and a .81 final ratio = 58.53 (G260)

215/40/17 (23.77") with a 3.64 and a .81 final ratio = 59.98 (G260

225/40/16 (23.77") with a 2.93 and a 1.0 final ratio = 60.36 (ZF)

225/40/16 (23.77") with a 3.64 and a 1.0 final ratio = 48.58 (ZF)

As you can see, the ZF/2.93 is gonna be about the same as the G260/3.64, with the advantage to the ZF kit in 1st gear. I think heavy traffic might be more suited to the G260 combo. I think the 260/3.73 would be fun too, but that tiny bit lower RPM just might be nice on the open road.

70 MPH with the 260/3.73 is 2989 RPM, while the 3.64 is 2917 RPM