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3.64 to 3.92 diff
Mog72 - 22/2/15 at 12:56 PM

Hello all, I'm looking for some advice, I have a 2.0 Zetec westfield (BGH heavy duty type 9) 205 BHP
Currently running a 3.64 lsd, am I lookng at a vast difference in acceleration fitting a 3.92 lsd?

inkafone - 22/2/15 at 01:30 PM

Difference will be marginal - better aero,lighter flywheel and wheels would make it a bit quicker - on the road 205bhp is ample in a light car.

ReMan - 22/2/15 at 01:38 PM

Try this
http://locost7.info/gearcalc.php

Ample is always slightly less than enough

Mog72 - 22/2/15 at 01:39 PM

quote:
Originally posted by inkafone
Difference will be marginal - better aero,lighter flywheel and wheels would make it a bit quicker - on the road 205bhp is ample in a light car.


Thanks for the reply, It has a lightened flywheel fitted, it does have 15" wheels, but I'm not looking to change them, I don't want to go to aero screen
As has been said before, look at the weight, alloy bell housing is about the only weight saving I can make I think
To change the diff on a Westfield looks a pretty easy task, I wouldn't mind trying to pick up a reasonably priced 3.92 to give it a try

loggyboy - 22/2/15 at 02:07 PM

Get a 3.92 non lsd, they are cheaper. Try the ratios, of it feels better pay bigger money for an lsd version.

snapper - 22/2/15 at 03:13 PM

Try the 3.9, I found a marked difference
If this is still not quick enough the tyres and or wheels can make a further difference
It's worth trying the options on a gear speed calculator

fesycresy - 22/2/15 at 04:15 PM

Put your ratios in the gear calc. but my gut feeling would be to go for it.

Incidentally you can save weight too this way.

You have a 3.64 which indicates a 7.5" not a 7" diff. You can get 3.92 in 7" or 7.5".

If you get a 7" 3.92, it's lighter than the 7.5" (I've heard 4kg but never weighed one myself) and you'll only need a 1/2" spacer for the top diff mount. Get the long bolt too, the 7" isn't threaded like the 7.5".

You can use the same driveshafts and prop with a WF, but, you must have a diff with lobros, open tripod type diffs won't fit with a WF drive shaft.

I'm about to merge a 3.62 LSD with a 3.92 open to get my 3.92 LSD.

[Edited on 22/2/15 by fesycresy]

Mog72 - 22/2/15 at 06:21 PM

quote:
Originally posted by fesycresy
Put your ratios in the gear calc. but my gut feeling would be to go for it.

Incidentally you can save weight too this way.

You have a 3.64 which indicates a 7.5" not a 7" diff. You can get 3.92 in 7" or 7.5".

If you get a 7" 3.92, it's lighter than the 7.5" (I've heard 4kg but never weighed one myself) and you'll only need a 1/2" spacer for the top diff mount. Get the long bolt too, the 7" isn't threaded like the 7.5".

You can use the same driveshafts and prop with a WF, but, you must have a diff with lobros, open tripod type diffs won't fit with a WF drive shaft.

I'm about to merge a 3.62 LSD with a 3.92 open to get my 3.92 LSD.

[Edited on 22/2/15 by fesycresy]


Thanks for the massive help !
So If I go 7 inch diff, I could only get an lsd ? Not an open diff ?

Ben_Copeland - 22/2/15 at 08:54 PM

You can get 7 inch in both LSD and open, but you'll have to be careful with the different shaft types.... bolt on or push in etc.


I've just changed from 3.9 LSD to 3.6 LSD because I wanted better cruise. With the power I'm running it doesn't really effect acceleration that much.

Matt21 - 24/2/15 at 12:14 PM

I have a indy with cbr900 engine

started out with a 3.64 open diff and switched to a 3.92 lsd
noticed a bit of difference in acceleration (quicker now) but my top end is pretty restricted now, I've lost maybe 10-15mph?

Ideally I would like to go to a 3.62 lsd, or if I eventually get a turbo an even lower ratio