Frankenstein

Lately my transmission started leaking between the main part where all the gears are and the back part as you can see in the following picture:


This seems to be a common spot for 6 speeds to leak, so i wanted to seal it up, but I didn't wanted to pull the transmission again.
As I couldn't find a Thread or a Video of the whole procedure I wanted to give it a go and try it myself.
I hope I can help some of you.

First of all you have to take out your center console in order to remove the shifter from the turret.
I wont go in full detail of how to do this, because there are plenty of Threads and YouTube Tutorials about it.


Now you can see a cover attached with four 10mm bolts, you have to remove these.


Right under this cover, there is the part, where your shifter connects to a long rod, wich will turn your motion of shifting in the actual process of shifting the gears in your transmission.
You have to remove that bolt as well in order to get the back part of your tranny out of the car. At this point you won't be able to get this connecting piece right out, it will automatically come out as soon as you pull the back half out.
Unfortunately I can't exactly remember if it was a 12mm or a 14mm bolt.


When you have removed this bolt, you are pretty much done from inside your car.
Now you have to get under your car and drain your transmission fluid (24mm Bolt), remove the mid-pipe of your exhaust and remove your driveshaft (4x 14mm Bolts and Nuts).



Now you go ahead and remove the Speedo Cable from the transmission as well as the wiring harness and the negative terminal that connects to the PPF. I've taken a few Zip ties to make the harness stay away from my working area so it won't disturb me.



Now go ahead and remove your PPF. To do this, you have to undo the three 17mm bolts that connect to the transmission, and you have to remove the two 17mm bolts that connect to your differential as well as you have to hammer out the two threaded inserts on top. Do do this, just thread in the bolt a few threads and hammer them out.
Undo your exhaust heat shield as well, I forgot to take a photo, but if you compare the following picture to your underside of the car, you'll easily spot it. It's held in with four 10mm bolts.

Here you can see how I zip tied the wiring harness away.

Thread out the 10mm bolt of the Speedo wheel and take it out.



Now have a look at your transmission, it should look something like that.


Now the actual part of removing the back half can start. In order to get it out, you have to unthread nine 12mm bolts.
The top left bolt is pretty hard to get to and candt thread out all the way at once because there is a switch in front of it, I'll come up with a solution later in this thread.
So go ahead and loosen all bolts and take record of wich you pulled where. Also loosen the top left bolt as far as you can.
Now you should be able to get that transmission-half loose. I've used a rubber hammer to gently make it come apart.
You can't get it out all the way at once, because of the top left bolt. You have to pull it out just a bit, thread out the bolt a few turns and so on, until you are able to get it out all the way.

Thats the top left bolt I'm talking about. Go ahead, undo the switch all the way and get the bolt out the hole and get the switch back in.

Now you transmission half is out and it should look something like this, laying on your floor.


On this photo the mating surface is already cleaned.

So now we come to the part of the solution I was talking earlier about, so we won't have any trouble with getting the top left bolt in.
As you have seen a few pictures ago I went ahead and removed the (top left) bolt completly.
Now I went to the hardware shop and bought a M8x55 Bolt (you can also use a longer one if you like, but i think mine is long enough).
I cutted of the head of the bolt.


After cutting off the head, I put a small amount of Loctite on the threads.


Now I went ahead and screwed the modified bolt in, in place of where the hard-to-get-to top left bolt was. I screwed it in so the threads will stick out 25mm / 0.98 inch
When installing the transmission just use a standard M8 nut and a lock washer.



Now you have to get the mating surfaces super clean. I like to use very fine sandpaper or abrasive fleece.
When you are done it should look something like this:
I only took a picture of the cleaned mating surface of the transmission, but you should be able to get an idea of how it should look like.


Now you can go ahead and get some RTV on the mating surface of the Transmission halt you took out.
I've used this sealant, its very common in Germany, just make sure its is approved for usage with transmission fluid and high temperature.


There are many ways of getting something sealed up with rtv or silicone, but I like to do it the following way:


Now It's time to give one of your mates a call to come and help you.
You have to go and get under your Car to stick in the ''Shifting-rod'', and your mate has to be inside of the car to get the connecter of the rod to your shifter in.
YOU HAVE TO DO IT THAT WAY, YOU CAN NOT PUT THE CONNECTOR ON LATER (just believe me, I've made this mistake for you guys and hat to take everything apart again)
Put the Bolt in using some Loctite.
Just to remember wich connector I am talking about:


Now screw in all the bolts and that one nut and lock washer. It should look something like that:

Everything full with RTV, I'll give it a clean when I'm done.

Now put everything back together the exact reverse order.
When you're done on the underside of your Miata, go inside and reseal the cover of the shifter turret:

You can see some RTV squeezing out.

Now fill your transmission back up. I use some 75W90 wich I bought at SPS Motorsport over here in Germany. (Check out their Onlineshop and their YouTube channel)
The Miata 6 speed transmission needs to be filled with approx. 1.75L of fluid.
You can fill the 6 speed Transmission right through the hole for the shifter.



And now you are pretty much done.
Just put your Interior back together and you can go out for some tranny fluid leak free skids ;-)))

IanIsInTheGarage

Nice and if you pull transmission out you can do this with 1 person. I love your sensor blocking bolt solution. When I reinstalled my sensor I broke the first one not realizing it was made of paper that looked like metal.

WigglingWaffles

I applaud the extent you went through to not remove the trans. Well done and good writeup!

Frankenstein

Thank you!
Yes but removing the transmission and reinstalling it is definitely more work to to!

Frankenstein

Thank you, I appreciate it!

sonofthehill

iTrader: (1)

No need to hammer out the PPF inserts. On either the tranny or diff side.