Considering a new transmission

[dave_from_Tennessee]

Hello guys,
I drive a '97 328i 4-door 5-spd manual. When I take long drives I will usually set my cruise control at approximately 80 mph on the interstate. Now with my current transmission this puts the RPM's a little over 3000. So, I've been considering getting a 6-spd transmission. I'm looking for any input with regards to a) how does the 6-spd feel and perform (i.e. what are the pros and cons?) and b) where can I find a reputable merchant to purchase one. I already have a good garage. I go to Urban's in Catonsville, and have been for a few years now. Thanks in advance for your input.

Dave

[mcoupemindy]

Hello guys,
I drive a '97 328i 4-door 5-spd manual. When I take long drives I will usually set my cruise control at approximately 80 mph on the interstate. Now with my current transmission this puts the RPM's a little over 3000. So, I've been considering getting a 6-spd transmission. I'm looking for any input with regards to a) how does the 6-spd feel and perform (i.e. what are the pros and cons?) and b) where can I find a reputable merchant to purchase one. I already have a good garage. I go to Urban's in Catonsville, and have been for a few years now. Thanks in advance for your input.

Dave

Dave,

In my opinion, there's really no sense in installing an expensive 6-speed transmission. The simple solution would be to keep the current transmission and reduce the differential gear ratio. This will allow for lower RPM's on the highway.

Just my $.02.

Jonathan Thayer

[dave_from_Tennessee]

Jonathan,
How do you reduce the dif gear ratio? Do you have to buy a new dif, or can you just purchase a new gear to put in the dif? I guess my other question with regards to this is am I going to lose some acceleration in the other gears by doing this?

[mcoupemindy]

Jonathan,
How do you reduce the dif gear ratio? Do you have to buy a new dif, or can you just purchase a new gear to put in the dif? I guess my other question with regards to this is am I going to lose some acceleration in the other gears by doing this?

The easiest way is to change the entire differential. This would be a great time to upgrade to a limited slip unit. You can either have one custom built by a builder such as Diffsonline.com or you could see what other ratios are available from other e36's.

Yes, you will lose some acceleration by doing this. It will make all of the gears longer. For example, sometime when you're normally in third, you might want the power available in second. Honestly, it's really not that noticable.

[woodym3]

Dave, I agree with Jonathan that the expense of going to a 6-speed tranny will not reap worthwhile savings on your gas mileage. The on-board computer on my E36 328 indicates over 30 mpg when cruising at 75. I suspect the rpms will drop by around 500 with the overdrive 6th speed.
For what it's worth, I recently made a trip in a friend's 6-speed E46 330Ci. 6th seemed to have lost all of the car's torque, and downshifts to 5th were called for on mild interstate hills.

[Car54]

+1..Woody...even my M3 was a bit sluggish in 6th gear.

What about just buying a set of taller tires. Maybe just an 1" total diameter could change things enough. Someone smarter than me can run the numbers, but maybe a 16" rim with 215/60 vs. 205/55...should be a better highway ride too.

[Nick325xiT 5spd]

Your fuel economy will drop at reasonable speeds with a 6 speed. You haven't got the power to drive it through the air at lower revs. (Keep in mind that operating near the torque peak is operating where the engine is most efficient.) AND the car will be 40 pounds heavier on top of that.

All in all, a 6 speed is a huge waste of money. So is a taller diff. Leave the car alone.

[OwnedbyDuncan]

Car is almost 12yo. It has no value as a collector car. Its not an 2002 which would benefit from a 5spd but then the value of the 02 would suffer. A really nice 02 just sold for almost $23k.

You will not recoup the cost in fuel economy gains in this half century.

Save the money and put it to your next ride, get your aelf a herding dog and buy your SO a nice pair of Jiimmy Choos and something nice from La Perla.

Dave Apker and the collies.

[jhm5]

I suggest setting the cruise control at 75. A six speed on that car is no short cut to economy. What would it cost? Will the six speed even bolt up to an E36 engine? Will you need a new driveshaft? The list goes on. Save the money for gasoline or a different car.

[tgmeyer]

6th seemed to have lost all of the car's torque, and downshifts to 5th were called for on mild interstate hills.

This speaks volumes to me. 3000 RPM's @ 80 MPH is not that high.

IMHO, you have been give many very good options: change tranny, change diff gears, or change speed.

Two questions:
1) What are you really trying to acheive?
2) How much $$$ are you willing to spend?
Answer those questions honestly and you have your answer.
Tom

[Nick325xiT 5spd]

This speaks volumes to me. 3000 RPM's @ 80 MPH is not that high.

IMHO, you have been give many very good options: change tranny, change diff gears, or change speed.

Two questions:
1) What are you really trying to acheive?
2) How much $$$ are you willing to spend?
Answer those questions honestly and you have your answer.
Tom

I'm not sure he can buy a taller diff than the one in the 328i/5 without going custom.

Even my M3 with a 3.64 rear gear is anemic in 6th at quasi-legal speeds.

[dave_from_Tennessee]

I appreciate all of your replys. I believe I'll let it be, and save my money for other things. The horrible roads that I have to drive to get to work have sped up the invetible suspension work that I expected to have to do with a car this age anyway. Incidently I don't have the factory 15" alloy's on her anymore. I have 17x8 BBS RK's. They really helped out. I don't know if the rest of you have noticed this or not, but my gas mileage went down when they started to add the ethanol to the gas. I now average between 18 and 25 on the highway, and it used to be about 25-30 and sometimes more.

[OwnedbyDuncan]

Ethanol I found got my mileage 10 to 15% especially in the summer.

You had more weight with your wheel and tire change. Also depending on the tire manufacturer and the model of tires your gas mileage will change.

Change the tires on a Prius to a good handling all season performance tire from Toyo or Yokohama and your mileage will drop drastically.

At 80mph in my Element I am above 4000rpm with my 5sp.

And I dare you insult our roads. they are in great shape compared to the roads in Georgia the country not the state.

Dave Apker and the collies

[87325is]

+1 to Nick325xiT's first post.

Dropping the rpms does not always help. If you are on the low end of the tq curve you are defeating the purpose if you are trying to save gas. You will most likely just use your right foot more to compensate.

Just get a diesel at the end of the year, ii wish i could.