RE: Original Gearbox Ratios????? Help?

[Alex Lipowich]

I'm trying to find out what he gearbox ratios were for US spec 318TI manual gearboxes.

I am especially curious if anyone knows the difference (if any) between the years of manufacture for these cars. Did all manual gearboxes for all years have the same ratios?

If anyone has their owner's manuals in the glove box, and its written out in there, please post and help me answer this question.

Thanks, (xyobgyn@aol.com)

Alex

[cossieturbo]

Hey mate. Here are the ratios for the 1995 ti 5spd and one of my friends tells me that all U.S. spec Ti's have the same ratios.
1st - 4.23
2nd - 2.52
3rd - 1.66
4th - 1.22
5th - 1.00
reverse - 4.04

cossiturbo

[TN.Frank]

Originally Posted by cossieturbo

Hey mate. Here are the ratios for the 1995 ti 5spd and one of my friends tells me that all U.S. spec Ti's have the same ratios.
1st - 4.23
2nd - 2.52
3rd - 1.66
4th - 1.22
5th - 1.00
reverse - 4.04
cossiturbo

Wow, big jump between 1st and 2nd. Seems like someone should be able to build a "close ratio" trans for the ti. Something that'll drop the engine rpm back to max. toqure rpm after max.HP rpm. If I could build one I'd use something like this:
1st-4.23
2nd-3.23
3rd-2.60ish
4th-1.50ish
5th-.9ish over drive or 1 to 1 depending.

Those ratios would keep the rpms closer from shift to shift(not that I'm an expert but common sense says it would) and you could even squeeze in a slight over drive if you'd like to cut rpms at hwy. speed. Any Trans experts i the house, chime in and let us know what the proper ratios would be to go from max. hp down to max. toqure per shift.

[Alex Lipowich]

Thanks for the responses.

Many people feel 1:1 in 5th is the strongest top gear mechanically you can put in the gearbox.

ie, swap diffs if you want to modify top speed/rpm, not the gearbox.

Gearboxs can't be everything to everyone.

what you might want for off the line pickup, and managing "drag races", may be different from what someone wants to race at the track.

Alex.

[TN.Frank]

So basically what you're saying is that these cars are made to race in 3rd,4th and 5th mostly with 1st and 2nd only being a way to get into 3rd gear. That's why 3-5 are so close but 1st and 2nd have such a spread on em'. Ok, that makes sense I guess.

[aceyx]

Originally Posted by Alex Lipowich

what you might want for off the line pickup, and managing "drag races", may be different from what someone wants to race at the track.

Or just driving around town.


I remember reading about the different Getrag and ZF transmissions that came in Bimmers, but I'm at a complete lack to recall any of the information. It's not an easy google search, but it's out there.

IIRC, the ti has a Getrag250, while the M3 / 328 use a ZF that's a bit longer in the tooth.

[bense]

Originally Posted by cossieturbo

Hey mate. Here are the ratios for the 1995 ti 5spd and one of my friends tells me that all U.S. spec Ti's have the same ratios.
1st - 4.23
2nd - 2.52
3rd - 1.66
4th - 1.22
5th - 1.00
reverse - 4.04

cossiturbo

interesting, i do lots of transmission work for hondas. I was wondering why people kept talking about low 3.45 and 3.25 ratios. Most performance oriented hondas have differentials of over 4.25:1

intesting in that bmw uses shorter gears in the tranny and a lower final drive. I wonder if that offers an advantage over traditional gearing setups that implement a ~0.7:1 5th gear ratio.

hopefully someone with given experience can chime in and cover this

most hondas have a 3.25:1 first gear ratio. this lower ratio is why they run such a higher final drive, JDM ITR final drive = 4.785 and b16s and b18cs have a 4.4 final drive.

very interesting.