3.64 diff on a 320

[kieron]

Hi

just wondering if anyone out there has ever put a 3.64 diff on a 320?

I just recently put new wheels on my 320 which i believe has a 3.91 as standard, but the circumference of the new tyres is smaller than the old ones.

i have noticed a bit of a difference in acceleration and the speedo is now out (now reads about 45 when you are doing 40 in 5th). I have one of Speedtouch's mild chips to go on the car and a hottuning manifold and stainless exhaust which altogether may add 10-15 bhp if im lucky.

do you think the 3.64 ratio would kill all performance?

thanks
Kieron

[ImysE30]

It will be a 4.10 open diff as standard IIRC

I've got a 3.46 and was told it would be too long, probably be same for the 3.64

[e30bmlover]

way.... WAY..... WAAAAAAAY TOO LONG!!

[Simon13]

it will be a road block with that diff, 320's need all the help they can get!

[kieron]

Are you sure its 4.1? if so theres no way im going for a 3.64, maybe a 3.91 instead. I used to do aroung 3500rpm for 70 in 5th i think. Used to be able to work out what ratios from reve but cant remember now.

[Rav335uk]

I would'nt mate, the 4,27 is right for the power of th engine, 3.64 will be waaay to slow on accelleration but good on the motorway, but imo not worth it.

[e30bmlover]

it will be a road block with that diff, 320's need all the help they can get!

too true si... even with a b25 under the bonnet its still rather long! out of interest what speed is a 3.64 geared to??

[Ziggy]

The tyre size is the reason your speedo is out - diff ratio has nothing to do with that.

I actually prefer a 320i with a long diff, like the early ones had. They're pretty pointless for performance either way, and longer gearing makes them more pleasant for cruising and improves economy.

[kieron]

just been reading the e30 wiki page and my 320 would have had a 4.10 in.

http://www.e30zone.net/e30zonewiki/inde ... ferentials

the above link says:

For 3250 RPM, 5th gear, 205/55/R15 wheels:

4.10:1 (318iS) final drive == 69.4 MPH 3.64:1 (325i) final drive == 78.2 MPH

so that makes it a huge difference, ill have a think about it. 3.91 would be the lowest i would go.

[Rav335uk]

it will be a road block with that diff, 320's need all the help they can get!

too true si... even with a b25 under the bonnet its still rather long! out of interest what speed is a 3.64 geared to??

Maybe naive, but what do you mean "Geared to"?

[e30bmlover]

whats the maximum speed the diff will go to without shitting itself lol

[kieron]

The tyre size is the reason your speedo is out - diff ratio has nothing to do with that.

I actually prefer a 320i with a long diff, like the early ones had. They're pretty pointless for performance either way, and longer gearing makes them more pleasant for cruising and improves economy.

i understand that it was the tyre size that had knocked the speedo out i was just thinking that changing the diff would help bring it back.

if the ratio was changed to reduce the acceleration by the same amount that the wheels have increased the acceleration the speedo would again read correct.

[Ziggy]

The speedo reading comes from the diff. Again; changing the diff ratio will have no effect on your speedo.

[Rav335uk]

whats the maximum speed the diff will go to without shitting itself lol

Well mine was worked out on here by on of the guys.

162mph without worrying it.

[kieron]

ah, i get you now. sorry it confuses me trying to work out the various ratios.

thanks
kieron

[e30bmlover]

whats the maximum speed the diff will go to without shitting itself lol

Well mine was worked out on here by on of the guys.

162mph without worrying it.

my point being a 320 just wont get there!! neither will a 325(unless shes got a blower or supercharger) it would be painful on a b20...

[ImysE30]

I've got 125 out of mine so far

[kieron]

maybe i should just get a b25 instead....

would be more fun

[e30bmlover]

I've got 125 out of mine so far

i dont drive that fast! christ mine gets to eighty... thats enough for me.

[Rav335uk]

I've got 125 out of mine so far

That's with the wing behind you and on a private road??
LOL

[e30bmlover]

I've got 125 out of mine so far

That's with the wind behind you driving off of a cliff??
LOL

sorted it

[ImysE30]

i dont drive that fast! christ mine gets to eighty... thats enough for me

Only did it once when i first bought the car, wanted to see how fast it could go

That's with the wing behind you and on a private road??
LOL

[e30bmlover]

i dont drive that fast! christ mine gets to eighty... thats enough for me

Only did it once when i first bought the car, wanted to see how fast it could go

ok saying that.... it was a little white lie... three digits can easily be achived(so i hear) from the sweet briar industrial estate lights on the ring road to the dereham road roundabout... not that iv ever dont it...

[ImysE30]

[Rav335uk]

I am planning on taking mine off the clock aqt some point now that its got the hardtop on

[ImysE30]

I wanna be in it for that

[stonesie]

I actually prefer a 320i with a long diff, like the early ones had. They're pretty pointless for performance either way, and longer gearing makes them more pleasant for cruising and improves economy.

+1

I have one on mine and it is nice to be doing 3K at 70~ish rather than the 3.6k it used to need, to be fair it dosent appear to have slowed it down at all on a 0-60, it will now get there on the limiter in 2nd (or slightly beyond on gas) which helps

I use the car as more of a cruiser than anything else really, not much point wringing the B20' neck while im still trying to decide how many valve's/litre's it's replacement shal have.

[StuBeeDoo]

I actually prefer a 320i with a long diff, like the early ones had. They're pretty pointless for performance either way, and longer gearing makes them more pleasant for cruising and improves economy.

+1
to be fair it dosent appear to have slowed it down at all on a 0-60, it will now get there on the limiter in 2nd

+2.
I had a 3.64 in my 320i Touring for nearly 4 years and did something over 50k miles with it. It most definitely doesn't turn a 320i into a "mobile roadblock". 1st gear with a 4.1 or 4.27 is a waste of space. The biggest problem with the 320i gearing is the huuuge gap between 1st and 2nd - and it doesn't matter what diff you have, that gap is always there.
As Ziggy says a 3.64 makes the 320i a far better cruiser (and cruising is what the 320i does best), and as Stonsie says the 3.64 doesn't appear to slow the 320i in day-to-day real-world driving.

[djk]

Interesting stuff. I was quite intrigued about this as a mod when I learnt that the early 320i had a taller diff. Agreed, as stock, 1st is pretty useless.

Not sure what those saying it would be useless are on about to be honest - changing the final drive by this sort of amount just means you would use different gears at different times, it's not as if you're stuffing potatoes up the exhaust pipe - sure, 0-60 will likely be affected, but when has that ever mattered in the real world outside of Max W*nker magazine?

Oh, and Imys, 125? On the clock son, on the clock...

[Rav335uk]

Oh, and Imys, 125? On the clock son, on the clock...

[ImysE30]

^^^

[DavieP]

... it's not as if you're stuffing potatoes up the exhaust pipe - sure, 0-60 will likely be affected, but when has that ever mattered in the real world outside of Max W*nker magazine?

Only to Max W*nker emulators - you know the types, dustbin exhausts weed-eater suspension and 24 hour front fog lights

Oh, and Imys, 125? On the clock son, on the clock...

Not saying when or where, but only once have I taken mine to well over the ton (on the clock, yeah I know ). At an acceptably rapidly achieved, indicated 115 it felt as though there was loads more to give. Then I remembered things like helicopters overhead and average speed cameras so I chickened out and feathered the stop pedal Got home, patted the steering wheel and muttered "Well done old girl, well done". Drove like a nun for ages after that just to give her a rest

[Speedtouch]

My 1987 320iSE had a 3.64 and was a pleasant motorway cruiser. It was a bit lame on acceleration though.