Best Diff for a Long Drive?

[cheffy30]

guys,

i currently have the original 4.10 lsd on my auto. love it around town. gas mileage sucks...
which diff do you recommend for a road trip from seattle to pasadena and back? what have been your experiences?
which diff will give me the best cruising rpm's and gas mileage increase?


thanks

[Metallated]

I'd say the 3.45 would be your best bet.

3.73 is still pretty short.

Also depends on wheel diameter...

[cheffy30]

sadly still runnin the 14's

[shootnjunky]

I run a 3.73 with my s52 swap and an overdrive 5th in the g260

I avg about 24mpg on hwy on my last 9 hour trip

And I’m running 225/45/15 which are undersized

[Andre3127]

sadly still runnin the 14's

He meant overall tire diameter, not rim diameter.

[e30davie]

Depends what engine you have too..

3.45 is nice on my m20b23 manual. it was originally an auto car, im not sure what diff the manual cars come with originally.

4.1 would be insane short with my m20b23 and getrag 260, but it might be perfectly fine with a m10 and whatever gearbox they have as the gearbox ratios are longer.

[ForcedFirebird]

My first e30 was an eta and ended up doing a stroker swap, but kept the diff. I loved the 2.93 for highway use. Drove that car for a 5 day road trip and it was great. Acceleration wasn't terrible, either. Was almost like starting out in 2nd with a 4.10, but you get an "overdrive".

[digger]

Longest will be best unless it's very hilly

[cheffy30]

i have a m20b25 auto, like i said with the 4.10lsd. it hits around 3500 rpm's at 75-80mph
tires are P185/65R/14 toyo eclipse

still the 3.45?