Swapping Differential Input Flanges

[TristanHunter]

I bought a 3.46 diff from a 325i to swap into my car, but found out that the 325 has a different driveshaft and input flange. So, I have three options:

1) Sell the 3.46 and buy a 3.38 with the matching input flange
2) Swap the input flanges (and possibly screw up the diff bearings)
3) Swap the driveshaft (more $$$)

I'm leaning towards swapping the input flanges, but that runs the risk of screwing up the preload on the bearing and wearing out the diff. From what I understand, the easiest way to do the is to measure the torque it takes to spin the pinion or to count the turns it takes to get the nut off the flange, then tighten the nut exactly the same.

Can anyone comment on how well this method works? Has anyone ever worn out a diff like this? Any info would be appreciated.

[Avetiso]

Everyone just swaps the flanges. I don't think it's as big a deal as you make it out to be. I doubt you'll ruin your diff or something.

[midlandtech]

Swap flanges... I still need to do this myself actually

taptalk + Note 3

[TristanHunter]

Everyone just swaps the flanges. I don't think it's as big a deal as you make it out to be. I doubt you'll ruin your diff or something.

Thats probably what I'll do then.

I had read that there was optimal amount of torque to keep the bearings healthy, but the amount varied for every diff. I guess there is probably a tolerance, so I'm thinking it should be alright as long as its close to the original torque.

Is changing the input flange seal necessary or should I reuse the old one?