Mazda Repair: 1990 Mazda 323 Manual Transmission, forward gears, hand pumps

Question
First of all, I would like to apologize if this question isn't in your field.  If so, I can move it somewhere else.

With that said, I have a transmission problem, which is peculiar.  I bought a 90 Mazda 323 awhile back and a couple weeks ago, I had tried to shift into reverse and was met with grinding.  I depressed the clutch as far as I could and it made no difference.  I had to move the car slightly for it to go in to reverse.  All forward gears work fine and smooth as well.  Now, to make matters weird, the next day I had started my car and tried to shift it.  It went in just fine.  I've noticed so far, that when the car is either hot or cold, sometimes, it just will not go into reverse, other times it goes in smooth.  I have done alot of searching to see if anyone else has experienced this, but found no relevant results.

Today, it did it again, when I went to a tire shop to replace two tires.  I had to shut the car off, put it in reverse, then start the car and back up to go home.  After I arrived at my house, I thought I would try it again just in case.  It also went right in.  I don't know much about transmissions, only engine problems.

I appreciate any help you can give.

Joel

Answer
This does not sound terribly abnormal for a manual transmission.  However, a gear oil change in for the transmission may be overdue.  You will probably notice that the transmission does not grind into reverse after you put it into first.  I almost always select first before reverse out of habit.

If you decide to change the transmission's gear oil, here are some tips on how to do it.  It should be possible to drain the fluid from a plug on the bottom of the transmission.  The plug is actually a bolt with a square head on it.  There will be another square-headed plug on the side of the transmission for refilling.  When filling the transmission, I like to use a 1 gallon (4 litre) jug with a hand pump and a 3/8 inch (10 mm) hose attached to it.  These hand pumps can usually be found near the gear oil in your local auto parts store.  Add oil to the transmission until it starts to spill out of the fill hole.  Replace the plug and you're done.