V8 hommies... what differential?

[bmk]

What diff is everyone running? I want something that will give me a good mix of highway acceleration and decent highway mpg (20 mpg). My car will be right around 400hp/400tq 3200lbs I am using a t56 6 speed 1st: 2.66:1 2nd: 1.78:1 3rd:1.30:1 4th:1.00:1 5th:0.74:1 6th:0.50:1
Curious on your guys input from guys that drive v8 e30's.

Thanks!

[e30_302]

2.93 for me, but I don't want to have to shift out of 4th on the tack. Had a 4.10 in it which was way too low. For a street car low 3's would probably be good. You can chart it out and see, what's what I did.

[bmk]

I can get a 3.15 z3 torsen locally for a good price. I'm thinking it may be just a little to low. But it's way better than the 4.10 I currently have

[The Dark Side of Will]

What diff is everyone running? I want something that will give me a good mix of highway acceleration and decent highway mpg (20 mpg). My car will be right around 400hp/400tq 3200lbs I am using a t56 6 speed 1st: 2.66:1 2nd: 1.78:1 3rd:1.30:1 4th:1.00:1 5th:0.74:1 6th:0.50:1
Curious on your guys input from guys that drive v8 e30's.

Thanks!

Assuming this is an LS swap...

3200# Corvettes and 3400# Camaros run 3.42 rear ends, but really wake up with 4.10's.

A <2800# E30 could probably run 3.15, 3.23 or 3.38 and get really good economy. You'd probably end up about 1500 RPM at 80 on the highway.
I think a 3.64 would be really good for performance in such a light car.
4.10 would be too much and first gear would be useless.

4.10's work better in heavier cars like E39's, though.

[bmk]

Yes it is an ls swap however it's of iron block variety which is a solid 100 lbs heavier than the aluminum counterpart and it is in a convertible which are heavy. Like I said before I guessing my curb it gonna be around 3200lbs and honestly that might be on the light side.

[bmk]

I've been looking for a 3.46 but they are hard to find for a decent price.

[The Dark Side of Will]

I missed your curb weight in the first post.

There are 3.46 medium case gearsets available... not sure any were used in E30 cases, though, so you may have to build one.

[jalopi]

Go here:

http://www.teammfactory.com/gear-calculator

plug in your tranny ratios and fiddle with the rear end ratios. Though I'll guesstimate you'll get good acceleration and at least 20mpg with anything other than a 4.10.

[bmk]

Thats a pretty fun site to mess around with. It says with a 3.15 I would be doing 1800 rpm @ 80 mph, where a 3.46 would increase it to 2000rpm @ 80mph with the 215/35/17 tires I currently have.

My theoretical top speed with in 6th @ 6500rpm with the 3.15 would be 282mph. Haha

[jalopi]

Pretty crazy, eh? Though at around 400 wheel the max speed would be more like 180ish (based off of a aerodynamics calculator I used on my car a while back) which is still fast as fuck.

The 3.73 works out pretty nice for me. It is a little noisy cruising at 80 (3k rpms with a ford t5) but when cruising (I've got it set lean-ish for cruise, maybe 15-16:1) at 60 I can get 18mpg. This is with a carb'd 302 with heads and a cam... you'll have no problem getting 20 (probably) with your slightly taller final gear and fuel injection.

[QUKBMER]

Im going to be using a 3:73 in my swap.

[The Dark Side of Will]

Corvettes can hit 30 highway mpg when carefully driven. An E30 has a bit more drag, but the 3200 curb weight is about the same. Corvettes have pretty tall rear tires... C5's run 275/40-18's.

IIRC, the 4th gen Camaro I drove turned 1800 at 80 with 3.42 rear and 275/40-17's. I wasn't paying for gas, so I don't know what mileage it made, but that's at a curb weight of about 3400. If 3.15 with 215/35-17's gets you about the same RPM/speed, then that's a very livable combo.

[Jack89i]

Whats that aerodynamic top speed calculator you used Jalopi? Do you just enter the drag, hp and gearing?

[jalopi]

Can't remember which calculator I used... I'm sure it's only my old computer, but that piece of shit hasn't worked in a good while.

If I remember right it asked for the frontal area, drag coefficient and amount of powah. Found the first two figures either here or on e30tech.


*** Found the site:

http://www.wallaceracing.com/Calculate%20HP%20For%20Speed.php

The figures I used were .38 for the CD, 20.9 sq/ft for the frontal area and 2800lbs for the weight.

[Wanganstyle]

some local clients:

1. E30M + 6000cc catalog LSX (600rwhp) + T56 + 3,46 final drive

2. E36M + 7000cc LS7 crate motor (500rwhp) + T56 + 3,46 final drive.

Both are street driven to the track by owners.

Some LSX swap fans like a 3,62 - 4,10. It all depends on the owners preference