M30 gearing questions

[E30SPDFRK]

What transmission/diff combo are you running and how do you like it? What RPM are you at at 80mph?


I'm running a 260/6 paired up with a 2.93 diff. Running around 2600 at 80.


It really isn't that bad of an all around diff for the car, but it is just too tall for me. I'm using the car as my commuter though and I don't want to mess up my highway cruise. I'm picturing a 3.25 being perfect, but I'd like to hear your opinions as well.

Also, are the ratios between a 260/6 and a 265 any different?

[RickSloan]

im about to put in a 3.73 so ill get back to you

[JoeMadoo]

3.25 is a good mix i think. You can still pull about 65-70 in 2nd gear.

[BenM]

3.46LSD

/end thread

But seriously, it really is the best diff for an M30 powered car. 78mph at 3000rpm in 5th gear is perfect IMO.

[RickSloan]

3.46LSD

/end thread

But seriously, it really is the best diff for an M30 powered car. 78mph at 3000rpm in 5th gear is perfect IMO.

problem is thats not the case depending on what trans your running

[BenM]

problem is thats not the case depending on what trans your running

Well technically you're right, but I doubt anyone here would be running a dog-leg 5-speed, or even a 4-speed. I was only commenting on people running an over drive (.81 final drive) transmission, which most of us here run.

[RickSloan]

some are running e30 m3 trans and others m10 5 speeds

but i know what you mean, i figured i would just point it out. And i actually have a 4 speed in my e12 and the thought has crossed my mind once or twice!

[E30SPDFRK]

3.46LSD

/end thread

But seriously, it really is the best diff for an M30 powered car. 78mph at 3000rpm in 5th gear is perfect IMO.

That's not bad at all. I would have thought the rpm change would be higher. This gives me hope for the 3.64 I have sitting in my garage.

[euroshark]

The 3.25 is a great diff for the 260/6 if you've got the extra power of a B35 turning it. It's comfy in my 535is but the US spec B34 just doesn't feel quite right. I imagine with a B35 and the weight advantage of an E30 it would feel perfect.

[e30_kid89]

Lol i was planning on running my 3.73 with my B34 and my 260/6.....am i crazy?

[RickSloan]

thats what im about to run so ... no

[Funkmasta]

I was running a 280 with a 3.46. LOVED. IT. I don't know about the rest of you, but 110 in 3rd is exciting enough for me. I never was able to top out 4th.
BTW, 280 and 260 have nearly identical ratio's.

[yert315]

OK since we're on the subject, I thought I'd ask..
I have been hearing all these different transmission names being thrown around. I know the g280 came from the ///M series cars, but the others are all confusing. g260, 260/5, 260/6, 265. There's no thread that explains each of these transmissions, what car they came out of, what the numbers indicate, or the differences in gear ratios.

And what do the /5 and /6 mean?

[euroshark]

The Getrag 260/5 came in the earlier 3.2 liter powered cars. 533i, 633CSi, and even some 733i I believe. I don't have ratios handy but the 260/5 has a reputation for not being as robust as the 260/6 and the 265, and sometimes makes some bearing noise upon shutting the car off that is known as the "265/5 rattle".

The 260/6 replaced the 260/6 and is regarded as a very robust transmission. They were used in pretty much anything that got an M30 built in and after 1985. The gearchange is generally agreed to be a bit smoother than the 265.

The 265 is the most robust family of transmissions available for the M30. The 265 actually comes in a 262 case (262 was a 4 speed box) but they have 5 speed guts. The 265s can be notchy sometimes, especially into 2nd gear (personal experience) but tend to last FORVER and can take tons of power and torque without exploding. The 265s were offered in the 3.5 liter 635CSi and E23 735i (europe) up to at least 1984, as well as some E28s. It seems that BMW used them here and there until around 1986 but thats not a definite cutoff. The 265 has a close ratio version with a dogleg patten that is very sought after and rare.

The 260/5 is a one piece case with an integrated bellhousing and a "checkerboard" pattern on the actual transmission portion of the case. The 260/6 is also a one piece case but it has longitudinal casting lines that look like cooling fins. The 265 is a multi-piece case with a removable bellhousing, so telling the three apart is generally pretty easy.

[ZM Blue Devil]

Ian,

Great info, in my searches I also found this doc, perhaps its helpful. Not sure if these are Metric Mechanic specific ratios or stock or its the same thing.

ZM