Can I put an overdrive 5th gear in my '93 525i?

[theirongiant]

My '93 525i has a 1:1 ratio 5th gear, but I would prefer a more relaxed journey with possibly an 0.92 or 0.85 gear. Can such a modification be made to an otherwise-stock manual transmission?

[winfred]

the fun-est but most expensive would be score a 6 speed from a euro e36 m3 and get a drive shaft built to fit it, otherwise a taller diff ratio would make highway driving better, lower #s = taller

[winfred]

i am eventially going to get one of these for my diesel http://www.gearvendors.com/ so i can have a double overdrive .73 allready but it redlines at 3k so double od would be nice 4-500 foot pounds of torque gives you some options , too bad they don't make them for bimmers

[theirongiant]

the fun-est but most expensive would be score a 6 speed from a euro e36 m3 and get a drive shaft built to fit it, otherwise a taller diff ratio would make highway driving better, lower #s = taller

But lower numbers also mean slower acceleration, so to counter-act this I would need to get a lighter flywheel. Is that correct?

[winfred]

yep slower off the line, flywheel wouldn't help much but 30-40 more hp would help counter it nicely if you didn't go too low with the ratio

But lower numbers also mean slower acceleration, so to counter-act this I would need to get a lighter flywheel. Is that correct?

[Kalevera]

As I think Winfred is saying, there's not a lot that can be done without spending a bit of cash.

The economical "upgrade" is a tradeoff -- slower acceleration/higher theoretical top speed.

It's probably not worth monkeying around with a high mileage 220 to begin with. I don't know what Bill or Winfred have to say about it, but it has always been my understanding that they're not noted for their durability.

best, whit