Q: Rear pinion seal leaking. Would i also need to change the flange?

The flange is integral with a splined yoke. The yoke segment (of the flange/yoke) has a precision, machined, highly polished surface which mates with the rubber seal. Since the rubber seal is spring loaded and is under tension against the polished surface, sometimes a literal groove can be cut into the steel.

In fact, such wear is so common, for other types of shafts such as that on crankshaft seal areas, aftermarket collars are vended to mechanics so they can "recreate" a smooth sealing area. So the problem is when you put a new seal on a (damaged) shaft (yoke, in your case), one where there is already a cut in it, the seal will basically leak immediately.

If once they remove the yoke, the area where the seal rode is undamaged, you can reuse the old flange/yoke but that can only be determined once they remove that part. It is unfortunate, but that is the way these assemblies work. Who knows, you may get lucky and find that the sealing area is pristine and you should definitely ask to see the old part before any decision is made.

Basically, if you draw your nail over the worn area, if such wear exists, and your nail catches at all, you’ll need to replace the part - otherwise, it will leak. You do also have the option of getting additional estimates from our estimator page to see if the overall repair can be done less expensively.