Auto Parts: Inter-changeable Front Differential? Astro/Safari, chevy astro van, gmc safari

Question
I have a 2000 Chevy Astro van VIN# 1GNEL19W6YB118507 and a 2001 GMC safari VIN# 1GTDL19WX1B503076. I am trying to figure out if I can use the Front differential off the Safari to put onto the Astro. Both have a button on gear shift for towing, but neither came with a 'tow package'. I have located a number 'imprinted' on the Case of each Front Differential, the numbers on them are a perfect match. According to all the VIN Decoder sites I have been on both vehicles were manufactured by GM and at the same Baltimore MD assembly plant. Are they 'interchangeable'? What do I specs do I need to locate in order to be sure this will work? Prior to ripping them apart and giving it a shot? LOL


Answer
    The only thing you have to concern yourself with is that they both use the same gear ratio.  The safest way to be sure is to take the covers off of both units and count the teeth on the ring gear and the pinion gear.  If both figures are the same on both units, then you are good to go (if they're different, then forget it).  Make sure you use a new gasket and some good quality gear oil when you put everything back together, don't try to silicone the gasket, it never works on rear ends and ends up leaking.  I would also recommend one of the many gear lube additives that are available, they tend to make the lube stick to things better, which is important as the contact area of the gears is not actually submerged in the lube.