3.9 diff - anyone tried one?
 

I've noticed a few people have mentioned changing their 3.6 CWP for a 3.9 CWP on a 7.5" diff. Man on here done the swap and if so what did you like/dislike about the change?

Also, for those still on the standard speedo cable drive, did you bother having it recalibrated etc and if so where did you get it done?

Also, is it possible to buy the 3.9CWP new still?

Cheers for any experiences

I put a 3.9 on mine because I'm using 18s and it just didn't feel right it would either wheelspin or bog down when launching it and In gear it would spin up too much.

Cheers for replying Dan.

I was trying to work out if it would be a worthwhile change when rebuilding the diff.

On 205/50x15 tyres the speeds seem to come out roughly ( assuming 6500rpm in Gear ) at :-

1st 41 ( 38 )
2nd 63 ( 59 )
3rd 92 ( 85 )
4th 122 ( 114 )
5th 152 ( 142 )

At motorway speeds it looks roughly like it'd be doing 5mph less for the same revs - seem small differences on paper but was interested to hear of your real world experience

Cheers

had you any other mods done at the beam to stp it spinning up dan?

im going to stick one in the track car :grin:

I have one and it felt like the car had a extra 100bhp straight away. Was amazed!!

I also have one for sale :0)

Ronnie, was that built in with your Bara VC or have you moved on since then?

Is the car noticeably more "revvy" ( for want of a better term )?

I've got a Bara 3.9 diff in my 3 Door and think it's awesome.
Rich

i always thought about fitting a 3.9,
but surely it ll just want to spin even more ??
def be a good mod if you ve a decent beam etc
i just cant justify a beam when my car is only a road car doin 2k miles a year

will be using a 4.1/4.2 mysel but that will be for 0/100 more off a b/road thing not top speed.you have too ask yoursell when you going too be using 100mph+ really?? apart from draging and motor way's/fast track's

Iirc my car sits at 3k at 70mph on 225/40/18s car accelerates a lot quicker doesn't feel uncontrollable when it spins up you can drive through it whereas before it would spin up and pitch sideways and crab which looked impressive but was tiresome when it would do it in 3rd in the dry. As said whatever I did it would bog/spin/tramp now it feels nice.

Here's a video of mine with the 3.6cwp (utterly shit time!!) you can hear it come on boost and try to spin

Check out this video on YouTube:<br/><br/>
And another (again shit :cry:)


Check out this video on YouTube:<br/><br/> I've not run the car again yet but it should be a bit better

My car has a 6 degree beam and gripper diff (235/35/18 at the time) amongst a few other mods ;)

IMO it depends on the wheel size. My car even with the beam etc was bad and I think it was the speed the wheel picked up when it span made it difficult to drive now when it does spin up it still accelerates instead of spinning up on the spot you can see from the pics I was having tramping issues but you can see it coming on boost in 2nd in the distance (I had nobody to video it :cry:)
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no harm to you but that looks like a bad start off.are you the same as me with the big right foot lol

allso get a wee look at your diff/lsd:top:

My 60ft time was consistently 2.6/8s didn't matter what I did but in my old Saff the 60ft were low 2s and I was gettin the same terminal with lower power.

I stopped bothering to run it because it was so frustrating all that waiting and pushing and getting that!! And it was the same on the road in the end I would just big revs and drop the clutch :cry::cry: hence getting the option to put the 3.9 in it :cry::cry:

The diff is fine, I think I might have fixed the problem and will get some better times next year.

Yes, I was thinking of the 3.9 more for lower speed corners on B-roads rather than standing starts.
Not so bothered about losing 10mph off top speed as long as motorway speeds aren't too noisy

Mine does 75mph at 3500rpm so it's not too bad at all.
That's reading 75mph on the Tom Tom
Rich

ive got a brand new 3.9 cwp for £200 ;-)