6 speed Swap?

[bobbyrose5]

Hey E30 guys,
Wanted to mention that I am a new convert to the E30 scene. Loving my car. Bought it from some guys that negelect such cars as these. I have been spending my time chasing all the little @#$ that the previous guys had done (like stripping a universal O2 sensor instead of getting the right one for the car).
Anyways. Loving the car. Recently moved to Texas from California so all the highways are long, straight and fast. The back roads are at 70 mph and the semi's drive at 80 mph!!! So I was wondering if any you guys have come across or have swapped in a 6 speed for these cars? If not, what kind of final drive gear ratio should I get? I dont know what my gear ratio is. It is a 1989 325I with the 5 speed Getrag. I do about >3000 rpm at 70 mph. Its not bad I am sure. Would like to get that 6th gear and maybe get some good gas milage. The current 5 speed is alright for having some fun but I find it to have a long gear pattern. I would like to track my car once in a while but its mostly a driver right now till I get another vehicle and make it a weekend racer. What would you guys reccommend? Is there a 6 speed or should i try changing some of the gear ratios and final drive.

Any thoughts?

[jlevie]

A 6-speed isn't going to lower the engine speed for a given road speed. The 5-speed in the car now has a .82:1 overdrive in 5th gear. I don't know of a BMW 6-speed that is any better. The car's differential is a 3.73 and something a bit lower would drop cruising engine speed, at the expense of acceleration.

[mpowerful]

Change your differential gearing to something like 3.64 or 3.46.

[LJ851]

The easy "fix" is a lower (numerically) rear end. This will make the acceleration slower and reduce cruising rpm.

The next step would be to fit an even lower (numerically) rear end and a 6 speed similar to what bmw pairs together.