At 114,000 in 2011 I changed the Transmission & Differential oil on my 2004 Manual 6 speed. The oil came out thick and black, with only the usual amount of metal flakes on the transmission drain plug. I noticed the shifting was a little easier. The new oil started to leak out of the reverse sensor on the transmission (which is mounted on the passenger side of the tranny and below the fill plug level). So I bought a new reverse sensor for $85, drained the tranny oil (which after 500 miles of use, was still clear) and installed the new one refilled the tranny with new oil. The leak stopped.
I HIGHLY recommend a fine point hook tool to use to detach the wires at their junction plug ins.
Overall time: 1 hour.
Conclusion: The new oil was thinner and leaked out easier.
Problem in design? My 1990 Miata had the same problem and its reverse sensor was mounted at the top of the tranny, so being low mounted doesn't make the problem worse, but it is a pain for the Rx8 to leak while parked. But Kuddos to Mazda because the Rx8 reverse sensor was easier to reach than the Miata's.
My local transmission shop was able to order the correct part.

 

I don't think so..mine leaked way before fluid change..

 

common issue on some earlier trans reverse switches. It shouldn't leak regardless. The potting appears to go bad and lose it's seal. Just replace the switch. It has been upgraded by Mazda.

 

its one of the easiest switches to replace

 

how much was this sensor? and what does it look like? My sensor is leaking aswell

 

Anyone know if this is covered under warranty? My extended ends in December, and I'm leaking out the back, too.

 

First off, sorry I necro'd this thread.. I can't seem to start new ones..

I will be replacing my Reverse switch on my 04 Rx8 MT in about two weeks.. She is sitting in the garage getting fired up once or twice a week to keep the battery charged for now....

Im wondering tho... It may end up that by the time I get the new fluid and switch, I may have dripped all the fluid out down to the sensor.. So, how much fluid will I still have in there as I will have to get my car about 2 miles down the road to lift her up for the job. Im guessing about 40 percent left?

 

Put a container, preferably with a fluid scale on the side of it under the tranny, voila !

 

There is a different thread someplace..

I found the sensor for $70. Christmas project was pulling mine, cleaning out the potted material (you want a dental pick like tool), and re-sealing with silicon. So far, so good.

I find it therapeutic and it seems people do not bother me when I have sharp tools in my hands....

 

Well it's been dripping a while now, so the collect and observe method wont really help me. I let her sit a week and the drip stopped, so I am guessing im finally down to the sensor.. Im ordering the part on Monday and installing it (and flushing new fluid) the following weekend... I was mainly just curious approximately how much is left once it drains to that reverse switch. It has been REALLY hard not to drive her while I wait on this repair. :/

 

Mijik, I would choose patience. The sensor is pretty far down as I recall. Not worth the risk. Good luck doing it in January- the oil gets THICK. Might want to keep the oil indoors (warm) until the moment of use.

 

what he said, most of the fluid is gone by the time it gets to the sensor. Look at the fill and drain bolts on the other side....

 

atkins rotary sells the switch for 70$.
I just replaced mine. quite easy and its a good excuse to change the trans fluid and toss in some redline...

 

That's where Im getting mine too! Got some Redline as well, should be interesting pumping that stuff in while its a nice 44F outside.. lol Oh, and its gonna rain.