While you're in there, REPLACE the two sleeves...their rubber seal against the divider plate is usually rock hard and brittle on old ones, and it's supposed to be pliable to make a good seal.

GM Part number 9796347 gets you a pair of sleeves for $20-ish. Any GM dealer, Amazon, Ebay...still in production and easy to find.

So many people seem to skip this step, and I'll never understand why...