Hello Again,
Let me be a little more specific. Sometimes when I first start up my car at warm up idle. I hear a wierd grinding noise, and the cluth engaged, or not, does not seem to affect the intensity of this unnerving grind. I don't know if that is related, but this problem has been happening for much longer than the noise from below my stick shift at high RPMs. This problem has been very intermitant, and goes away for weeks at a time.
The problem I believe is trannie related has symptoms like this: It does seem to be all gears, and downshifting does not help. It is most noticeable when I accelerate, and drops off remarkably when I let off the gas.
May or may not be directly related: After driving some distance on the freeway, when I slow down into traffic areas, I feel a strange sensation from the back end when I turn, especialy from a stop. Like uneven dispersement of traction. This is one reason I am worried the problem might not be only the transmission, or that I am completely wrong, and maybe the drive train, u-joints, or differential could be the problem. I love my RX7, and it has been very good to me, but I need to find a way to slowly start restoring some tired areas of my baby, to allow my limited income to handle all these possible problems. I am a technician for a high school district, here in California. I am not a mechanic! I do service a wide range of school equipment and machines, including network solutions, very successfully, but I can tell my RX7 will be very challanging for me to bring back to it's awesome former self. I have a factory service manual, and have done a wide range of work on automobiles. No rebuilding of engines or trannies, but enough repairs to be dangerous. Taking my baby to a mechanic would finish me off financially, so here I go. Thank you all again, for trying to help a lost individual. Please be patient and a little understanding of my lack of knowledge and inexperience on these issues.
PS What does S4 NA mean in reference to transmissions?

 

S4 means - series 4. 86-88 model years are S4, and 89-92 model years are S5.

As far as your noise. I would first inspect the U-joints. The end attached to the tranny cannot be checked without removing the drive shaft. The drive shaft is easily removed by taking out the 4 bolts securing it to the differential, lowering the heat shield under it, and sliding it out towards the rear of the car. You will need to look closely at the area where the "u" attaches to the shaft, at both ends. If your noise is coming from here, the damage should be obvious. Next you can inspect the rear differential mount. In your FSM, it should be pointed out in a few of the diagrams. Any large noticable cracks or missing chunks could indicate a bad mount. Replacing the mount might be more work than you are willing to take on, but one man can do the job in a long weekend with normal tools. I would not suspect the differential to be causing your troubles, but it is always a possibility. Another option which might be the easiest solution would be to change your tannsmision fluid. A few have had good success with eliminating noises by doing this. The noise could also be from a bad pilot bearing, which would require a whole clutch R/R. The worst case senario would be a bad tranny, although I highly doubt it.

Most if not all of the parts you might need can be found at:

www.mazdatrix.com

 

You are correct in saying that it is not just tranny related. Based on what you have said it could be either drive shaft or your diff or even both. If you are hearing at idle then it could be your clutch assembly. If you have the manual it is not that difficult to do, the difficulty lies in whether you have proper tools and access to a lift, with out those then it will be a pain in the *** to do.
A S4 NA means a 86-88 RX-7 Naturally Aspirated or in easier terms non-turbo.

 

Thanks so much for your time taken to address my issues. DVLS-7 your car is awesome! You have done an excellent job restoring, and nice paint and wheel choices.
Both of you, have made some good points, and your information will be very helpful. Where are both of you located?
My brother origionally hooked me up with my car, it was a trade in for a Lexus, where he was finance manager. Someone had just replaced the engine, and it was a great deal. The cluth went out not that long after I bought it, but these resent problems come after a long period of reliable driving, from a great car.
I did have a mechanic here in Redwood City take a drive with me, and he was convinced it was the transmission. He is the one who replaced my clutch ( I believe he also replaced something else at that time. He said it would be foolish not to replace this unknown part with the clutch replacement. If I remember correctly, the part looked like a solid pipe, a drive train or something that looks like it.)
Do U-joints have a "normal" lifespan they are expected to last? I am assuming all of the transmission, drive train, and the differential are all origional parts. Is one of these areas more likely to fail after a period of time like this? What kind of symptoms does one find, with failed U-joints or these other areas?
My delima with the expenses of repairing my RX-7 back to it's glory, is a question of me my challenging experience. How deep would I begin to find myself in debt, without a ride. I want to eventually have my car restored. Currently my RX-7 is my only transportation. Would I be better off, to go out and purchase a new car, or more resent, used car. (The 350Z seems like a very nice car; out of my range?) Store my RX-7, and I could wait for a time when I can afford to do this right.
Thanks again, for everything.