3.46 w/ 260/240?

[jakeb]

I am currently running a 3.73 with my m50 and the getrag 240. I do A LOT of hwy driving and would like to bring my cruising rpms below or very near 3k to help with econ. I am around 3300 or so at 75mph and getting right around 23mpg.

I also just bought a s52 and will be swapping that over in the summer so will be upping the power soon.

Would a 3.46 be a good combo with the 240 or 260 trans? Would it get me below or near 3k rpm but not loose out on the accel?

I am going to start with the 240 with the s52 and if it doesn't hold up I will switch over to a 260


TIA,
jake

[rThor432]

Yep it is pretty much the ideal gear for an OD transmission on a street driven car that sees a decent bit of highway driving.

Your acceleration will be nice. It will really help with low rev driving when you are out of the powerband. My S52 is somewhat doggish below 2.5k with the 260 and 2.93.

Not sure where I am in the rev range at 75, but your 3300 at 75 with the OD transmission sounds low to me.. Not as low as mine, but low for a 3.73.

[PiercedE30]

Sounds like the same RPM's that I run with my 260/3.73. With my 4.10 I was running right around 3600-3700. Pain in the ass.

[jakeb]

Would a 3.25 be to low?

From my calculations a 3.46 would be at 3100 at 75, with the tires I run
a 3.25 would have me at 2900 rpm at 75

rThor: you have a 2.93 with a 260 and a s52? That seems really low....how is it? What are you at on the hwy, what sort of econ do you get?

[etxxz]

no, i'd do 3.25, even consider a 2.93 with the s52 is you do a lot of hwy driving. it'll still move pretty good

[jakeb]

what are you running? I think a 2.93 might be a bit low but the 3.25 might be a good choice

[etxxz]

i think he'll do better with a 2.93, but a 3.25 is ~ 300rpm higher and also a good choice.

car gear Calculator
i believe your 5th gear is 0.81:1 and 4th 1:1 you'll know what to do

http://www.unixnerd.demon.co.uk/revs.html

[PiercedE30]

Hey, I've even had a 3.25 in mine. I wanted to try it out, so I cleaned one up and threw it in there. Honestly, it's not bad for cruising. The only bad thing, was gas mileage wasn't as good as I had hoped for, mainly because I had no tune, but also because I was having to put more load on the motor to maintain speed, due to the longer gearing.