The Ford 9" can handle about 500 lb-ft of torque. 1200s like Rigoli's 9-second ute, or Waylands electric-powered 2-dr sedan require this kind of strength.

For Ford 9" prices and a little more info, see the Tech Section article What Diff and LSD should I use?.

if u fit a 4d 9" it would b a disadvantage to big nothing wrong with a borg warner 78 or as some know as 8 & 3/4 they go alright behind4d xa's thrugt to au falcons or holden vl to vr old fords 25 spline new 28 sp all holden 28. best diff for 1200 con is a 28sp skyline use the disk brakes and all i use to work 4 diff trans spares in sydney dun heaps of cons.

You should put in the lightest diff that is strong enough (with a margin of extra strength). There's no advantage in making the car heavier than normal.

For example, the Ford 8.8 has 95% of the strength of a Ford 9 inch, but weighs something like 30% less.

For a road or road-racing car, having less weight under the springs will help improve handling and give a smoother ride.

OK, there's one advantage to the heavy diff -- if you can get one inexpensively compared to a lighter but more expensive one.

No, you are pretty well right there. Did quite a bit of ringing around yesterday, and have decided to go for a VN onwards LSD. I thought I might just change my stock diff's centre for an LSD one, but I am looking at $2500 for a new one, or $1200-$1700 for a second hand one....Commy diff is now on the cards, and hopefully it will be nice and strong. Has anyone had any bad experiences with them?

Leigh

yeah ford 9inch is a big diff heavy and takes a lot of power to turn you migght kick my idea in the guts and thats cool but this is what i did i brought a VP commy diff for 400 bucks and spent 600 getting it shortend stud pattarn changed suspension mounts modified and then use the commodore brakes i got with the dif pretty cheapf

I think what go_the _datto is getting at is the housing and axle shortening is the part that will cost you the money...the $1850 'custom one' is not made from scratch, it's just a shortened 9". Only difference will be that you will be suppling them the axles and housings.

I am aware of that, considering how much narrower a 1200 is than any ford that uses a 9" diff from factory!

I dont think you woll get any 9 inch diff to fit with out modification, their all too wide

Ok, so now that I have decided on an engine and gearbox combination for my 85 datto ute (Series 5 13b turbo), I thought I might actually swap the diff out for a Ford 9" job while I get all the other parts together. Now, what I need to know is, if I am looking around for this diff, what should I be looking for, ie. should it be out of a specific car, does it need to be a 9" that has certain parts, etc on it? I am doing it this way, as it works out a bit cheaper than having a custom one made ready to bolt in. I got a quote for this today and it was $1850 complete and ready to bolt into the ute, add to this another $200 for skyline rear brakes with a handbrake setup.
So yeah, if anyone knows which one I should look for in particular to suit the suspension setup/layout of a datto 1200 ute, information would be appreciated.

Thanks.

Leigh