I use a from-scratch recipe that adds a box of pudding mix. It also contains sour cream and oil.

I have ZERO customer complaints about the moisture of this cake, but frankly, its very hydrated. Dare I say  "wet" on the bottoms.

I have posted several items about all of my frosting troubles and now, at 1am before another cake is due in the morning, staring at sides that are falling off, air bubbles and cracks...I can only imagine that the moisture in this cake is the root of all dessert evil.

I typically store, crumb coated, in the fridge but today I left it out. It was WET.

So which do I try to reduce first to cut down on some of the moisture? The pudding, the oil or the sour cream? Thanks!

I would reduce the oil, it is generally what adds the moisture to the cakes, from my experience. :-) Good luck!

Maybe look at your sugar ratios too.  Too much sugar will make a wet cake.  Sugar is hydroscopic, absorbs moisture from environment.  boxed pudding's first ingredient is sugar.  Could be sugar combined with the pudding sugar is too much.

How are you treating the cakes out of the oven? 

Without knowing your recipe, it is hard to give advice on what to tweak......

see fridging it dries it out some so leaving out that step left all the juiciness in there so maybe just go back to fridging your cakes going forward would help

what about switching from sour cream to buttermilk for a better emulsion -- just if you are going to be testing

All great tips!

I let them cool, wrap them (cool) and freeze them.

There is 300g of sugar to 325g of flour. I felt like that may be excessive with the pudding...but no one ever mentioned the cake being overly sweet.

My first thought was to reduce the 75g of oil. But really, I'm not sure whether oil or sugar or pudding or what!

If you are using traditional creaming method, it could be over creamed. 

If you are cooling your cakes without adequate air flow, that could be to blame. If I leave my parchment round on while cooling when I bake egg yolk only cake that contains butter & whole fat buttermilk & sour cream I have experienced that problem.

Fridging a crumb coated cake and experiencing dry out, that would be a severely thin crumb coat. Having it out overnight and wet, that would be high humidity in the room.

Possibly because of using unbleached flour instead of bleached?

without knowing the balance of your recipe, can't guess what if anything is out of whack.

 the ingredients and their quantities you have given seem similiar to Winbeckler's French vanilla sour cream cake. I have never baked it, so I am unfamiliar with it. But you could look that one up to compare and go from there..........

Yes! I leave the parchment round on! Largely to give it some stability when wrapping and handling it.

When I worked in a mass production bakery the cakes were always cooled in their pans. And so that's what I've always done. Do you advise taking them out?

How do you know if you have over creamed?

I've seen Winbeckler's before and yes, it's almost identical. I will Google their recipe and see what issues have come up, if any, for others. 

Great advice, thanks!