Differential

Moderators: Aceman, ecosselynx

Nickyb16
Posts: 6
Joined: Sun Jul 12, 2009 8:22 pm

Differential

Postby Nickyb16 » Sun Nov 01, 2009 9:18 pm

I have recently fitted a 4.2 triple carb into my MK 2 240, I need to upgrade the diff to a higher ratio.
Does anyone know which way to go.
Has anyone got anything, or can anyone suggest anything.
I live in West Yorkshire.
Thanks for looking

ecosselynx
Posts: 265
Joined: Sun Sep 02, 2007 12:08 am
Location: Magnou, France

Postby ecosselynx » Sun Nov 01, 2009 11:28 pm

Hi

For a quick fix, you should be looking to pick-up a rear axel out of a 3.4/3.8 automatic, these had 3.54:1 ratio differentials. Or re-build your own differential using a 3.31 crown wheel and pinion out of an XJ differential, this is a little more difficult as you need to get a bearing for the front pinion which is non-standard.
I don't have the number with me at the moment but can get it for you in a Month if you want to go that route. I went that route back in 95 and am happy with it, your pulling 2500 rev at 70 mph as a rough guide. I have heard of people running 3.07:1 differential, but I felt it was to high geared for the motoring I was to be doing.

regards

John H.

smiffy
Posts: 157
Joined: Tue Dec 09, 2008 11:52 pm

Postby smiffy » Tue Nov 03, 2009 11:41 pm

Hi John
That's quite a big jump from 4.55 or 4.27 to 3.54, but I do find my 2.4L Mk2 to be under-geared (it is a MOD with a 4.55 diff). Is there no down side to this change of axle ratio on a 2.4L, apart from having to get the speedo recalibrated?
David

ecosselynx
Posts: 265
Joined: Sun Sep 02, 2007 12:08 am
Location: Magnou, France

Postby ecosselynx » Wed Nov 04, 2009 2:40 pm

Hi David

For the 2.4, you may want to consider the 3.77:1 which was used in 3.4/3.8 MOD cars and should therefore be easy to get hold of. I find my 3.4 handles the 3.31:1 quite easy and is not over geared, I can run in 5 gear (same ratio as OD) happily at 50/55. Yes it's better to have your speedo re-caliberated, but I would wait until you try a ratio that you feel suites your car before having it done, just my thought.
If you need any other info let me know.

John H.

ecosselynx
Posts: 265
Joined: Sun Sep 02, 2007 12:08 am
Location: Magnou, France

Postby ecosselynx » Wed Nov 04, 2009 2:49 pm

Opp's

As for down sides. I don't have any, but then I'm not into dragging off the lights. Obviously you initial acceleration is not the same, but were talking 40 year old cars. I make trips from Scotland to France in my car fairly often, leaving jockstrap land 07.30 and catching the 17.00 tunnel, in the two day trip I clock-up 1120 miles, so I'm not getting in anyone road either.

john H.


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