Concerning differentials.

[Johnny540]

I was thinking about swapping out the stock differential in my e34 ... Dinan suggests a jump from 2.89(?) to 3.15, but I don't really think I'd see much of a difference. I was thinking 3.64 would be a better choice.

Anyone have any experience with either differential? My concern is the effect on gas mileage, and top-end.

[E34nication]

I run a 3.64... It is pretty short... I previosly got about 19 MPG and now i get around 15.5-16MPG. The car hits redline in 6th at about 162MPH now.

I have a couple of videos that i made holding my camera (very shaky and very low quality of the speedo and tach) going from a slow roll in 1st to the top of 2nd, and from about a 30mph roll in 2nd to the top of 3rd. I can get some more too, if that would help. Didn't have much traction through 1st and 2nd but it gives you an idea of the acceleration from about 5mph- to a little over 50mph. No place to host the videos but I could email them to you when I get home.

I also have a L/W flywheel, though, so that helps the motor rev a little also.

[Johnny540]

Thanks for the quick reply.

162 MPH, huh? You must have a chip, too, because I thought it'd be limited to 155. And I was also under the impression that you'd LOSE top-end, not gain it. Haha.

I drive the same exact car as you -- 1995 540i with the six speed -- and only get about 17.4 mpg. Huh.

I think if you can contact a mod, he can host the videos on the forums... I'd really appreciate it.

Thanks, man.

[E34nication]

Thanks for the quick reply.

162 MPH, huh? You must have a chip, too, because I thought it'd be limited to 155. And I was also under the impression that you'd LOSE top-end, not gain it. Haha.

I drive the same exact car as you -- 1995 540i with the six speed -- and only get about 17.4 mpg. Huh.

I think if you can contact a mod, he can host the videos on the forums... I'd really appreciate it.

Thanks, man.

I do have it chipped.... before it would cut out at 128MPH. After it was chipped the car would hit 140MPH in 4th Gear and 102 in 3rd (at close to 7k rpm's). I'll see about the vids when I get home... I will also see if I can get some better ones.

[Johnny540]

Sweet.

I guess the best way to make the 540 hustle a little more is a chip and the 3.64 differential.

I was having a discussion on the best way for 0-60 acceleration out of the 540 on a different forum, and I suggested a better differential. The cons were lower top-end and worse fuel economy.

I guess since you can go over 160 miles an hour, lower-top end is out of the question.

But 3 less miles per gallon might be a deal breaker.

[E34nication]

Sweet.

I guess the best way to make the 540 hustle a little more is a chip and the 3.64 differential.

I was having a discussion on the best way for 0-60 acceleration out of the 540 on a different forum, and I suggested a better differential. The cons were lower top-end and worse fuel economy.

I guess since you can go over 160 miles an hour, lower-top end is out of the question.

But 3 less miles per gallon might be a deal breaker.

my 15.5-16 MPG is city with me driving the car pretty hard. The 3.64 is very short and traction does become a serious issue in 1st gear. I want to bump up to a 9" rear wheel and put some 275's on. I am currently running an 8" rear with 255's. The 3.15LSD is also a good option. I am going to change to that once I find one for a decent price just because I want the LSD... I auto-x and do some track events every now and then so it is needed. Under hard cornering the inside tire will break lose in 3rd.

oh... and i got my diff out of an e31.

[Johnny540]

Ah, it's an open differential. That'd definitely explain the loss of traction -- but better gripping tires would combat that.

I was looking at diffsonline.com, and I think they have the 3.15 LSD for about 400 (used) and a 3.64 open for the same price.

Both look really appealing, but I don't know about the quality of service from an online site.

[Johnny540]

Oh, they reduced BOTH to 345 from around 415 earlier in the week.

Hot damn.

I might get the 3.15 this week.

[sdwhitney]

Where in Gods Green Earth can you drive 162 mph? (except the Autobahn).

You are some brave dudes. I am going to chip mine, although I have an automatic, just knowing I can go that fast is nice, but I would never get there.

I will get to about 110 or close to 120 and with as many cars here in No-Cal I freak out like a little girl. :eyecrazy

With changing your diff did it improve your 0-60 or 0-100 at all?

Would love to see the video of you getting to that speed though. Can you email it to me at sdwhitney@msn.com ?

Thanks

[Johnny540]

Haha, I know what you mean. I wouldn't ever DO 160 miles an hour, but the mere fact that I COULD is very comforting.

But, hell, in the 540, I was doing 120 on the 52 East and didn't even notice. Hot DAMN it's smooth.

[E34nication]

wow that's a good site... i will pick up a 3.15 lsd for that price. At 162 the car was still accelerating (albeit not all that quickly) but if there were more rpm's to be had it would have gone faster.

[Johnny540]

But they probably only have one!

You bastard.

[E34nication]

But they probably only have one!

You bastard.

just ordered it :)

[Johnny540]

Eh, life goes on.

[MaloventEvil]

vids!!!! also, i want to know how the 3.15 diff upgrade is. first gear is short as it is, wouldnt the 3.64 diff make it rediculiously short? (like redline @ 20mph?)

[MaloventEvil]

please do me a favor, whats the redline mph at the top of each gear with the 3.15, and whats the rpm @ 80mph in 6th

[E34nication]

Eh, life goes on.

check your pm's

[E34nication]

If you guys will find a place to host some videos I will make some comparing the 3.64 and the 3.15.

And I didn't think 1st gear was short at all with the stock 2.93 gearing

[E34nication]

Just so you know, the 3.15 LSD that works for the e34 540i is the same diff used in the e32 750il and the e31 850i. My 3.64 diff is out of an e31 850.