yeah they often get stuck. Remember it's old. They haven't made a TG1860 in a couple decades as I recall.
remove the assembly from the tractor, clamp it tight in a vise and heat it. if it don't come loose heat it some more. If it don't come loose by time it starts to turn orange, it's not going to. Replace it if it's still available. They usually come loose though with little heat. Once you get it apart clean everything up and repaint it, then reassemble, install it back onto the tractor and then go level your deck. 0" difference side to side and 0" difference front to rear, that always works great. You can let the front of the deck down about 1/8" lower but your cut will suffer a little bit, but it'll use a little less power to cut. Probably never notice power loss. Measure the back of a side blade and the front of the middle blade to get your F-R measurements. Side to side is obvious. Yes measure the blade--a lot of folks measure off of the deck shell, but the deck shell don't cut grass the blades do.
I hated them when they were new (the whole mower) and I hate them today. They ain't a bad mower but the power steering sucks and the front axle often wears out, so when you are trying to hold a straight line in the yard, you're constantly turning back and forth correcting, like driving an old Dodge. Even new I had a hard time staying straight, in comparison to the mowers that they replaced-the G1800/G1900/G2000 series. THOSE...were great. I've had several. Unfortunately their downside was RUST on the mowing deck, which is why I got rid of the one I had. Let someone else deal with the rust while I cut grass with a zero turn, which is about 40% faster mowing time and cuts nicer and more comfortable.
