2 M86 diffs - difference in pinion position

[3Katz]

Hi Guys, been a while!

 

The old BA RTV has been going brilliantly - 740hp these days and in the process of a 4L80e conversion.

As it it putting out some power and I've started running radials (and a transbraked 4L80) I'm a little concerned I may damage my factory locker M86 diff.

I bought what was supposed to be a BA XR6 Turbo ute diff from a wrecker down South with the view of rebuilding it with a Trutrac and straight swap the diffs out so I can keep my factory locker diff unmolested.

This is where the lid started to pop off the can of worms...

Upon receiving the diff I pulled the back cover off and noticed it has 2.73 gears not the 3.45's I expected, so I assume it's a BFII diff with the ZF gearing?

Secondly, although the measurement from flange to flange is the same (1505mm) the diff casing itself is 30mm to the right of where my RTV diff is, effectively the pinion is 30mm further to the right! I measured the center of the pinion in the ute to the chassis rails and the RTV pinion is exactly in the center of the car. If I were to install this replacement diff the center of the pinion would be 30mm to the right.

 

Weird right?

I have 2 questions - how is this so? And would it be a problem?

[xr6tForMe]

That does sound strange.

 

I would expect that the tunnel should be the same position in all BAs, so the pinion should be in the same place on all BAs?

 

Could the diff be from an FG?  Not sure if the pinion would be in a different place on them?

 

Not sure if 30mm movement would cause a problem, but I think you would want to figure out why it would be different to what you have.  All I can think of with that is that universal joints have limits on the angles they move though.  You might want to look into that.

 

I have a BA wagon diff at home which I can measure if that helps at all.