What is the feasibility of adding a 6th gear to a manual 5 (BMW318i)?

Question

I love my fuel sipping 318i. but driving here in california, we're often at the 75-80mph range, at which time the engine is revving at 4000rpm+. seems to me that an additional gear would allow me to cruise at an even more efficient lower rpm.

Answer 1

i would suggest swapping the rear diff for a higher gear. your car probably has 373 or 390 ratio. try a 293 or 323 gears. this will be a big difference. you will loose a bit of low end performance but will gain your lower rpm at 75-80 and better gas mileage.

Answer 2

I had a 1993 BMW 318i (E36) and the engine turned 4000 rpms in 5th gear at 85 MPH. The engine is designed to be high revving and while I wished for a 6th gear - I never entertained notions of such a thing.

The newer BMW's come with 6 speed manuals as standard equipment. If you can afford it - get a new 3 series rather than throwing thousands at a new tranny or a new rear and introducing new issues to your reliable daily driver. Good luck.

Answer 3

The fift and sixth gear ar over drive. In city driving you would see six gear and in some area you would not use fiftth gear. Cause they are to high for the engine rpms of the engine to run smoose. So you would be down in fourth or thridth gear to keep the rpms high. It is like a big rig over the road truck. 55 mph is to low to run in 13th or higher gear. When the truck is really a eight speed. The gears above are over drive to save fuel and run the engine at a low rpm. Six speed is nothing new. They have been around over seal. I had a six speed on the tree in Germany. The car was build in the sixty's. You can always have a three speed installed, or four speed. It is not work it is fun. To know you have a top end well over a 165 miles per hour and not over work your engine. Or have more power than your gears.

Answer 4

Seriously, it's not worth it. You are probably going to have to replace the transmission, at considerable cost. Then when you come to sell it, there is a good chance you will lose money again. People tend not to like to buy cars where people have messed around with them extensively. Something like this would put off a lot of buyers, and thus push down the price of your car. You could easily lose 5-10% of the value of the car, depending on the age, and waste the money changing the transmission. You may also have to waste additional money if the new transmission has any unexpected negative consequences.

Just save up, and trade up.

Answer 5

It is not very feasible at all to add a 6th gear to your existing tranny. Your best bet would be looking at a tranny swap, using a tranny that already has a 6th gear, but I am not sure what would work the best. You would be looking at a bell housing adapter and a decent amount of custom fab work. Also, you might run into problems with the shifter location, shaft input, etc. Probably more work than it is worth. Check around on the BMW forums to see what people have done.

Answer 6

yes, a transmission swap would be the only feasable way to add a gear, but take a close look at the gear ratios for your 5-speed and the 6-speed. The final drive ratio may be the same with each transmission. You may have to look at rear-end gearing to get better mileage/ lower rpm at speed.

Answer 7

Which year? E-30? E-36?

Depending on what year your bimmer is - you may be able to swap out a 6 speed manual transmission from an M3 (same generation). That would not really be a simple task, but it would be feasable.

Answer 8

I think the car is fine in the design specs and a sixth gear might seem good in your mind but frankly its not worth a major expense.

Answer 9

youd need to replace the gear box to acheive that but maybe looking into an overdrive might be worht while i know a few places uk but none in the states