The lovely and unfortunately blogless Jo-Ann writes:
"I have a 13 month old son who sleeps great. We part time co-sleep and he sleeps part of the night in his crib. The only issue is that to get him to sleep in his crib he sleeps in his infant car seat still! (He is little, only 18.5 lbs.)
Let me give you some background. My little guy spit up tons for a long long time, and he would not sleep lying down. Eventually they put him on Axid for reflux and things seemed better except for a constantly running nose, and he was a shy and clingy baby. A few months later around his first birthday we gave him yogurt. He was instantly very ill and covered with hives and throwing up. Finally we see an allergist. He was blood and skin tested. He is allergic to dairy, eggs, wheat and peanuts! I am still nursing so as soon as I gave up the offending foods and I got the offending food out of his diet he turned into a more social, way happier baby that never spits up.
The one issue left from that time is the car seat in the crib. I can nurse him down and try to put him in the crib. As soon as I do he is up and screaming (and he is a scream till I puke type). If I put him in the carseat he goes right out. Soon he will be grown out of the carseat so I want to have him transitioned by then. Also my husband puts the kids to bed a few nights a week when I work and he is heavily dependent on the carseat for sleep.
My almost 3 year old is starting preschool in the fall and I figured that I would give the crib without a careseat a try for his AM nap. I am hesitant to try this in the afternoon nap because the 3 year old who is still a GREAT napper is in the next room to the baby and the baby not sleeping would disturb him, and most of the time the baby naps with me in the afternoon. I work a few night shifts a week and usually need to nap with them for my sanity.
Any advise on how to get him out of that carseat would be very appreciated."
I'm so jealous that your 3-year-old still naps so well.
This could be a relatively simple problem, or it could be more tricky. It depends on what aspect of sleeping in the carseat your son is attached to. If he's attached to the actual carseat, then you might be screwed. But if he's just attached to the conditions the carseat creates, then all you have to do is recreate them in a way that he won't grow out of. (You know how I feel about all this stuff--as long as he's sleeping and you're sleeping I wouldn't care if he slept in the carseat until he's 45.)
If he's attached to the actual carseat, then I really have nothing for you, and you're probably going to have an extremely rough 2 weeks until he adjusts. So you probably want to labor under the assumption that it's just the conditions the carseat creates that he's attached to. If you can mimic as many of those as possible, it might not be so painful to switch him out of the carseat at all.
My guess is that the incline is a huge part of what he's adjusted to, so that would be the first thing I'd try to mimic. You could try a Tucker Sling (a wedge that puts the baby at an angle as he sleeps, with a sling to keep him from sliding down to the bottom and ending up in a sad crumpled little heap). Or, if you don't want to spend the money, you could try your own crib-propping experiments. I'd try either a firm pillow, a rolled bath towel, a bolster pillow, or a big swimming noodle, depending on the angle you're aiming for. Put whatever object you're using underneath the mattress to prop up one side of the crib, creating an angle similar to the angle the car seat provides.
He's probably also used to the fabric of the carseat cover, so I'd take it out of the carseat and have him sleep on it in the crib. (If you know someone crafty with a sewing machine, you could get the person to cut and resew it as the top piece of a blanket you'd put in the crib for him to sleep on. It would look kind of stupid, but no more stupid than sleeping on a car seat cover.) Stick to the same washing schedule and materials you usually use for the cover, since he's probably really used to the way the cover smells and would be disturbed by a radical change.
The only other aspect of the carseat I can think of is the way he's kind of nested and snuggled into it. You could try a Snugglenest or something else that would give him some walls around him. Depending on how strong and mobile he is, you could put rolled towels around him (assuming he's big and strong enough not to be trapped by them) as walls. It may not come to that, though, as I'm betting the key aspects are going to be the angle and keeping the cover.
Both of my kids, for whatever twisted reason, have been more receptive to sleep changes at night than during the day, so if I were the one doing this project I'd start at night. But you know your boys and what will work best with them. And, you know, you could always make the first night of the Big Switch one of the nights you're at work. Not that I'm endorsing that, of course (especially if your partner's reading this). Good luck with the switch, and let me know how it goes.