I have a v8 5 speed BA RTV ute, after doing big launches with the diff lock on the diff finally gave up (after 123,000km). It had snapped the pins holding the spider gears and locked 1 of the gears, so the others were grinding around it, was okay with the lock on, but otherwise terrible terrible noise.

Being M86 the centre from the xr8s and xr6t fits......kinda. I got a centre out of a BF xr8 sedan that had low kms on it. First issue was new carrier bearings, ford wanted $200ish, bearing company charged $40. Next the rtv centre is actualy around 10mm longer, so longer shims/thrust washers need to be made for the carrier bearings. So i made up new shims, figured out preload and backlash, all fit perfect, throw the right axel in and it fowls on the spider gear shaft! Doh!
So then i had to turn 5mm off the right axle, and offset the centre by 5 mm (move thrust washers around) and make up a spacer for the ring gear to offset that 5mm back to get the right mesh on the pinion, and to also get full spline engagement on the left axle.

The diff hat has like 2 arms off a vacume plate which engages the previous lock, so i just chopped the arms off and it all bolted up fine. It took 2ltrs of oil and is a dream. LSD is nice and tight, and makes the power very useable around town, really improved the driving experience.

So if you dont want to spend $1500 on a new centre, have access to a lathe, mill and surface grinder, it can be done!

Well done. Thats very clever what you did, and great way to save cash on new diff for ute owners.

I guess those are the differences between a live axle centre and an IRS centre.

doesnt removing the diff lock defy half the purpose of an RTV?

It doesn't sound like he used it for its intended purposes, hence the break, and the cheaper alternative.

So will this work for a BA Falcon sedan differential which has 3.23 diff gears I'm trying to put 3.08 into for a speedway car

BA XR8 Ute centre and axles probably would have dropped straight in......

The entire rear axle wouldve bolted up without any issues, so unless the donor car had a bent housing or other significant rear end damage, I dont understand why the OP didnt just swap the whole thing over, but kudos to him anyway for making it work.

Hello,

The RTV has a wider track. Not much, but may have been a factor in the choice.

the wider track is achieved by different offset wheels, which is why you generally dont see RTV's with anything except the steel sunraisias or the 5 spoke alloys, standard AU-on wheels run too close to the top ball joint.