Transmission problem on 88 rx7

[Brannonrx7]

I have an 88 rx7 and i drove it for a year with no problems then about 8 months ago my transmission went out. I got it rebuilt and fixed. drove it for 4 months and the trans began to whine so i replaced the bearing and it still whined eventually i checked the fluids and they were fine. Then it kept getting worse so i got the trans rebuilt again. 2 months later the whining came back and this time with a wierd noise sounding like it was grinding when the clutch was released. i sent it back in and and got the clutch and trans replaced. once again 2 months later same thing. I have checked the fluids ad they are fine. I love the car but i hate to have to keep spending money on it. also someone who "knows it all" in my town told me to check the rear end... Idk if that would help but im not for sure ... if u can please help