2001 Honda Civic Hydrophobic Car.

I have a car question that I would like to see what you think may be wrong because I have been dealing with this problem for about a year and a half and my mechanic is completely out of ideas.

The problem:
My car doesn’t want to shift between gears. What it dose it this. When it is working well, it will shift between all gears like it should. When it is having light problems it will shift between 1-2-3 fine, from 3-4 it will stick in neutral and not let me in 4th. What I mean is in pulling the shifter back from 3rd to 4th when it hits the neutral position it is like it encounters something hard and will not slid into 4th like it should. Sometimes it will slide into 4th but it feels like you are pulling it through something every thick like a stick in mud. When it is really having problems it will feel thick and stick in all gears but will still hit that wall from 3rd to 4th.

Background:
I own a 2001 Honda civic 2door coupe with a manual transmission. I got this car about 4 years ago and until last year had not had anything out of the ordinary go wrong with it. About a year and a half ago I was driving my car when I noticed that it was getting hard to shift between gears, having had many manuals this was something that was known to me. I took my car strait to my local mechanic that I have been using for many years and dropped it off. After explaining what the car was doing, he said that he would have his transmission guy take a look at it and give me a call. I got a call about a day later and was told that I needed a new transmission and he suggested gong ahead and replacing the clutch and the fly-wheel at the same time. I did all these and got my car back and for about 24 hours it worked just fine, then I was out driving and the shifter started to stick again. So my car went back into the shop and he said that an assistant put in the wrong fluid and that he had replaced it with Honda certified fluid and it should be good. And for about a week it was then it started to do it again. Needless to say my car has been in and out of the mechanics for the past year and a half and has just about everything transmission related replaced. As of know it is my observation that the transmission acts up only when it rains. Every time it rains the shifter gets all sticky and will sometimes "dry up" and fix its self all on its own.

My thoughts:

I think that it has something to do with the rain; it was a cold and rainy winter last winter when I was having the most problems with it and every time it rains the car starts having this problem and if it is hot and dry for a long time the car has been known to "fix its self". I have tried many times to get it to my mechanic when it was raining and have as of yet been unsuccessful. He is out of answers for me and about all he dose it put it up on the lift and grease up and loob up everything he can think of. I am looking for any help I can get to get this fixed. Any thoughts or suggestions would be greatly appreciated and a solution would be beyond my wildest dreams.

Thanks

Nate