Diff flange probs & pinion pre-load - KM

Have finally got a very good diff for my Omega, but the flange is smaller than on the one I have removed and therefore the bolt holes dont align with prop flange. My car is a late '96 and the diff I am fitting is a '94. I assume it was beefed up over the years or perhaps its off a 2 litre.

Anyway, has anyone experience of differential flange swopping? and how critical is the pinion pre-load? Can I do it, or will it really have to go to the main dealer to be set correctly, as it says in Haynes?
Diff flange probs & pinion pre-load - Andrew Moorey (Tune-Up)
The pre-load is absolutely critical if the diff is to work properly and last any time. As to whether your local main dealerhas the expertise to do it I am sceptical as it is a long lost art. You would be better off sourcing an axle rebuilding specialist to set it up. Quaife come to mind.

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Diff flange probs & pinion pre-load - KM
Thanks for the reply Andrew.

Is there anyone out there who knows why there are different flanges and are they interchangeable?
Diff flange probs & pinion pre-load - KM
To answer my own question in case anyone else here ever needs to know, the depths or thicknesses on the 2 types of flange are identical to the thou'. The flange diameters where the oil seal locates/operates are also identical.

Therefore the only difference between an Omega 2.0 and 2.5 differential unit is the bolt hole size and spacing on the pinion flange. The flanges can be interchanged, and the pre-load set to exactly how it was before dismantling.
Diff flange probs & pinion pre-load - Peter D
This is a used diff and you are only changing the input drive flange so why the question about pre-load, are you infact stripping the diff and overhauling it or just changing the flange.

Regards Peter
Diff flange probs & pinion pre-load - Cliff Pope
I don't know anything about this particular car but the normal reason for pre-load being critical is that there is a collapsible bush inside, and the flange nut has to be tightened to exactly the right torque to collapse the bush to give the right pre-load on the bearings. If you loosen the nut you have to start again with a new spacer. If you are replacing the same flange (eg to replace the oil seal) you can sometimes get away with marking the nut position so that it goes back on with exactly the right original pre-load, but with a different flange that might not work.
Is it possible to use the other prop so that you avoid the problem?

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