M50 + zf 320+ 373 diff= no highway

[e30 blue]

Okay so like Im going 60mph and the motor is at 4500 on the tach. What diff do I need to be able to drive on the freeway. I think 3.46 diff could work, what car did this come from? So I thought 16 " rims would help out but it doesn't. First gear is like useless and I can drive in 5th from light to light. Any Help?

[Devin1205]

get something from a eta, around a 292 or something?

[mbonder]

3.25:1 will get you closest to stock ratios

[mazur]

3.25:1 will get you closest to stock ratios

+1 for best choice for you.

[WADE30]

I have M50 + ZF + 3.25 LSD and it is perfect!

[funcrew]

My '69 Chevelle SS had a 3.91 diff and a big block, and obviously no overdrive. Brutal on the freeway, 8mpg or so. This was normal during the muscle car era, nobody thought anything about it.

[Bimmerman325i]

I'll trade my 4.10 for your 3.73 hahahahaha

Seriously though, the 3.25 (or 3.23, so close it makes no difference) is the stock M3 diff, but a 2.93 is iirc about the correct rear diff for an M50. I'd go with the 3.25 personally, better acceleration at negligible rpm hit compared to the 2.9x.

[jrdeamicis]

I ran a 3.73 for a while... Onto a 3.46 now.

1st is NOT useless, you just need decent tires and be pretty quick at shifting. It is FAST.

[etxxz]

fast to go through gears, but not faster.

[jrdeamicis]

fast to go through gears, but not faster.

I disagree. Its all about what you are trying to do, jumping out of a dig the 3.73 is the shit.

[87e30]

I ran a 3.73 for a while... Onto a 3.46 now.

1st is NOT useless, you just need decent tires and be pretty quick at shifting. It is FAST.

Well tits.... look at your sig. 6 speed, 3.73, and s50.

[jrdeamicis]

Well tits.... look at your sig. 6 speed, 3.73, and s50.

The 3.73 and the 6 Speed were AMAZING.

With a 3.73 every gear pulls like one shorter.

5th like 4th
4th like 3rd....

So 6th was fantastic.

[Wh33lhop]

I disagree. Its all about what you are trying to do, jumping out of a dig the 3.73 is the shit.

Not if you've got an M50 dual mass flywheel. :p

[e30 blue]

Thanks for the information guys.Ya I am running the m50 dual mass.It is good to see what others have run and what they have experienced. Do I need to change the whole diff ? or can the gears be changed? Like in town it is fun but a lot of shift work from light to light . If I need to go on the freeway then I am back to my gas sucking truck. The m50 swap is good as my m10 was on gas (in town that is).

[MattM]

running same setup as you with dualmass and a 2.93

roughly 65mph in 4th at 3500-4000rpm.