Diff bearing preload on 540i LSD

[BrianH]

Ok,
I've read the section on Bruno's site regarding the diff swap (great write-up). I'm swapping out my 2.93 open diff for a 3.15 LSD out of an '88 750iL. I know I need to install the input flange off of my open diff on the LSD. Question is, how do you properly set the input bearing preload? I've read that you can make match marks on the nut and the 750 flange, back off the nut, then torque it until the match marks line up, measuring the torque as you do this. Then, install the 540 flange and torque to the same setting. Is this the correct procedure? I asked the dealer if they could do this and how much it would cost. The shop foreman (a really decent guy, actually) is out today but will call me tomorrow with an estimate. I wanna do it right, but if I can do it myself and be confident it's done right, I will. Any thoughts or suggestions?

[632 Regal]

it would be best to find out what the torque is to crush collar and tighten the new flange to 2/3 of that figure and use red loctite.

The thing you dont want to do is crush it any more than it is or you will ruin the bearings thus the 2/3 figure with loctite. Also the initial torque needed to crush the collar is greater than one that is already crushed into position.

I wouldnt use the marks idea because your using a different flange from a different rear end and its possible the tolerence in manufacturing may be a few thousanths different.

[winfred]

ditto on all bases


it would be best to find out what the torque is to crush collar and tighten the new flange to 2/3 of that figure and use red loctite.

The thing you dont want to do is crush it any more than it is or you will ruin the bearings thus the 2/3 figure with loctite. Also the initial torque needed to crush the collar is greater than one that is already crushed into position.

I wouldnt use the marks idea because your using a different flange from a different rear end and its possible the tolerence in manufacturing may be a few thousanths different.

[BrianH]

Thanks guys. Sounds like good advice. I'll check the torque on the 750 flange and go 2/3 - 3/4 of that. That should keep from ruining the bearings. I can't wait to feel the difference with the new diff and UUC shiftkit I'm installing at the same time!