I posted this in the wrong section so re post . I have a AU with 507000 ks on it a still not a sound from the diff even has the original wheel bearings in it were as the BF has only got 170 000 odd on it second set of bearings and now whines like a ex wife . my question is will they swap over axle to axle swap . The AU is a 1tonner manual and the BF is a auto . thanks in advance Iain

Bump .

Let me get this straight.......you want to put the AU diff into a BF ???.....is the BF a ute too ???.
I think the rear brakes are different....if it's an AU1......AUII may be the same...?..anybody chime in ???

Yes they are both utes , I know the brakes and wheel sizes are different that I can live with . It seems according to Ford even, that the BA\BF diff is far weaker than the AU diff . I use the ute in a courier company in northwest Tassie around 96000ks a year and most days up near 800kgs . Iain

BA/BF diff weaker ??????......how?, why?.....a standard BA/BF puts out way more power than a stock AU series engine......beggars the question....why is it weaker????

As I said this vehicle is a work unit . Not a car ,its carrying a 6' high by 6' wide by 8' long Pantech that weighs 240kgs plus load of up to 800kg each day . The Ba\Bf diffs are fine for cars , s\wagons or the play utes but are not up to hard work with the wind drag from a Pantech . The Au diff has a lot more support around the bearing mounts for the centre area . The total load is still under the Ford posted limit for a cab chassis . Iain

I'd use this oil in it................... http://www.thefarmstore.com.au/media/ca ... e_2616.jpg

change it every 20-30,000km, if it's under that sort of load consistantly.

Putting an AU diff in a BA or BF is a smart move. I'm about to do that with my taxi. The AU diffs were well made, and last for years.

I'm not an expert on diffs, but inside there are pinion gears. These hold stuff in place. Ford diffs have always had four pinion gears, but Ford cut costs and dropped it back to two pinion gears for the BA and BF. This is partly why the BA/BF diffs don't last as long as the AU ones did. I'm pretty sure that the FG ute has gone back to four pinions.

However the handbrake brackets are on different locations on the AU and BA/BF diffs. You'll need to get someone to cut the brackets off and then weld them back on in the correct place.

If the AU diff has ABS then you can also use those axles, but if the AU diff doesn't have ABS then you'll have to transfer over the BA/BF axles. Why? Because you'll need the ABS discs on the axles.

While you're at it, get some Timken 2985 bearings and get someone to fit them to the axles (around $60/pair). You can cut the old ones off with an angle grinder and hammer/chisel, although I'm less violent and use a press to press the old stuff off. You will need a hydraulic press to press the new bearings on.

Drain the diff oil and put some good synthetic stuff in. A healthy AU diff with decent diff oil will last for years.

Photos on how I changed rear axle bearings: http://www.fordforums.com.au/showthread.php?t=11418260

I'm in the middle of doing this. The AU's 4 pinion centre does fit inside the BA BF Diff housing. You keep everything from the BA diff, just change the centres over.

The AU has a 4 pinion diff centre and the BA has only a 2 pinion centre. Thats why BAs have a reputation of breaking diffs, not because they are hectically powerful

Just to go a little more off topic, I believe this was also the case with the 4speed autos, the AU units were stronger than the B series. Something to do with the planetary gears. As ugly as it was, the AU was one of Fords toughest most reliable Falcons.

I'm currently doing the opposite to this changing my au lsd to a
Bf series 3 wagon m80 diff wich has been converted to 3.9s and LSD every thing is bolting up fine including tail shaft only thing which I'm having problems with now is with my original au ute brakes, the rotors for fine but my caliper brackets are rubbing on the rotor on the on the out side there is a 4 mm gap on the inside from rotor to caliper bracket, I've made sure the rotor is on properly too. Any suggestions why this is happening ?

Use an M86 diff from an XR8,Pursuit or Turbo ute. These are much stronger than the AU diffs of any type.
They have an 8.6" ring gear and 4pins and a proper LSD with 30 spline axles. You can still get problems as with any of them but they don't just snap like the others.