4.10 ratio to 3.91 ratio vs 4.10 ratio to 4.27 ratio

[kevin316i]

I changed my 4.10 ratio open diff to a 3.1 ratio LSD in my 316i as there is only a 4% diff in the ratios and the 4.27 LSD was twice as expensive as the 3.91 one. I haven't really noticed a decrease in acceleration, but I just have this nagging feeling that maybe I should have got the 4.27 LSD instead. I'm not into 'spirited' driving so I thought the 3.91 LSD would be fine at the time. The money I saved by getting the 3.91 LSD paid for most of my sport interior.

Is it worth the hassle and expense to get a 4.27 LSD?

[kevin316i]

Sorry there is a typo in the first line of the above post, should say '3.91' instead of '3.1'.

[Jimbob]

If you're a spirited driver then the higher ratio is better sideways action.

As you're not, then the 3.91 is the best bet as it lowers the revs resulting in better fuel economy.

[Demlotcrew]

you put a big case Diff onto a 316i?

Andrew

[kevin316i]

No, I got a small casing 3.91 LSD from the States. The guy had three in stock!

[Jhonno]

you put a big case Diff onto a 316i?

Andrew

anything wrong with that?! lol

I think you did best with sticking to the 3.91LSD from the sounds of your drivin style

[Demlotcrew]

you put a big case Diff onto a 316i?

Andrew

anything wrong with that?! lol

I think you did best with sticking to the 3.91LSD from the sounds of your drivin style

Its 15kg more in weight over the small case.

I found that i was changing gears too much around town because of the nature of the M42 engine, on a 3.91 ratio diff.

Andrew

[Markymarc]

I also got a big case diff in my 318i, never looked to see the ratio, all i know is it came out a 325i and cost me Ԛ£20
makes the gears seem longer, revs lower at higher speeds, but have noticed the slower acceleration

[M3Compact]

Was the 4.27 a large case diff'?

How much did they want for it inc' delivery to the UK?

Small case LSD diff's are more common in USA.

Link?

TIA.

[radback]

are small case more noisy?
My large case 3.73lsd was a little noisy, but my 4.10lsd small case is very noisy (I feel i'm in a race car)

[kevin316i]

The 4.27 LSD was small casing also. Cost was about $500. Shipping for me was $250 and I had to pay VAT on the cost of the diff AND shipping

It's probably cheaper to buy in the UK, but small casing LSDs are almost impossible to find so thats why I looked in the US.

Can't remember the link to where I bought it sorry, it was a few months ago. I don't think I'll forget the costs in a hurry

[SeamanStaines]

I put a 3.64 big casing 325i diff into my 320i which had a 4.1 small diff. Diff goes straight in once you've slackened the propshaft collar nut and pushed the prop in on its splines about 20 mm. I've found that the car goes better with the taller final drive. It now has somethiong to get it's teeth into and does 70 mph in second at the rev limiter - 60 in second is only 5500 rpm.

Small casing diffs are shite. They just aren't strong enough for anything with decent power or torque. I have a small trickle of small casing LSD's from Germany and they make Ԛ£200 every time.

[kevin316i]

Do you find your'e doing most of your driving in the lower gears? Do you need to do much downshifting to get decent acceleration for overtaking?

[M3Compact]

Small casing diffs are sh*t. They just aren't strong enough for anything with decent power or torque. I have a small trickle of small casing LSD's from Germany and they make Ԛ£200 every time.

Small case diff's should be fine for most 4 cylinder motors, it's torque that they don't like.

They weigh loads less and 'lose' less power too.

[Demlotcrew]

Small casing diffs are sh*t. They just aren't strong enough for anything with decent power or torque. I have a small trickle of small casing LSD's from Germany and they make Ԛ£200 every time.

Small case diff's should be fine for most 4 cylinder motors, it's torque that they don't like.

They weigh loads less and 'lose' less power too.

thats why i changed back to the small case, much better!

Andrew

[SeamanStaines]

Well I suppose when you've only got 130 odd bhp you need all the extra horses you can find......

Never had that problem in a 325i to be honest.