Need to save on GAS, 6 speed?
 

Where I live in Montreal Quebec Gas is through the roof!
The Ti is really bad on 5th gear revving at 4+ on the highway.
I own a manual 5 speed and actually look for a sixth sometimes.
I make a long daily commute.
Anyone successfully modify their existing transmission to a 6 speed?
Can the existing tranni be modded to 6 gears?
Simply adjusting the differential would most likely make the low end really slow.
I have read some threads on this but nothing substantial.
Anyone?

Swapping the diff would probably be your easiest for ya. Never heard of anyone modding the tranny.

You could get a euro 6 speed tranny but not sure if it would bolt right up...?

You can't modify the trans for 6 gears. A 6spd trans from a euro M3 or US E46 330i would probably be easiest but would probably cost around $2000 USD. Is that worth it for a few more mpg?

My ti can get 34-35mpg when I'm driving all hwy with 3.73 gears and keeping it around 70mph. I'd imagine a 3.25 rear end would be a great compromise towards more efficiency without sacrificing too much performance.

Also, ditch the giant heavy wheels. That alone made a HUGE difference for me, 3-4 more mpg, and much better handling, acceleration, and braking.

yeah, my 17's took off like 3mpg and the handing - accelerating went to crap. i just love them so much more. haha.. might have to go back to my 15's and 16's soon. money is tight

I drive a lot of city miles, and my diff is 4.44. With 17" alloys, I was averaging 16mpg. Switched it back to 16's, and was getting 24mpg. I miss my 15" steelies which were getting me 26mpg in city. So ya, wheel size makes a big difference in all the categories spider mentioned.

Tire diameter and width matter wheel size not so much.

If you buy narrow tires mileage will go up, tires that have a diameter that keeps the stock gearing help as well.

Wide sticky tires = less gas mileage..

Tires that use higher pressure tend to get better mileage as well.

Dave

I got the stock 3.44? rear diff. And the next step down with out going to a medium case is like a 2.xx out of a diesel, say maybe a 316d. Need to compare six speed ratio with the stock gear box.

The six speed from the e46 is same ratios just adds a .85 6th gear. Not many options at all for taller small case ratios. Plenty of medium case ratios available.

The bad is the M4X is not a torque monster so adding a 0.85 overdrive is just gonna bog that engine. It's designed for autobahn speeds where you are high enough into the hp curve to use it.

Dump the heavy wheels.

I get into peak mileage at about 3300 rpm.. Bad tie choices cost money... LOL BTDT..

Dave

Alright, E30 318's 5th gear is .80. 6 speeds are .85. You loose the close ratio but gain overdrive. Im looking to go down this road. I can keep the small case diff, and the 5 speed is lighter then the 6 speed. Perfect..?

Are you saying the e30 318 gears are longer then the e36?

edit, speaking of the transmission, not the diff.

No matter what gearing,,, it takes X amount of HP to move the car, My 6 spd in my 330Xi only buy a couple hundred RPM from 6 to 5..

Buy some narrow 17 inch Michelin's and put 45 lbs in them and you'll get more mileage back.

The 6 spd is also a fairly close ratio IMHO splits the gears nicely, but the car has way more power than a TI...

Cheers and keep us up on the result,,,

Dave