Manual Transmission Fluid Change

There are many ways to change the fluid in your manual transmission, but not very many of them make it easy to get out the majority of the fluid.

This problem is compounded with the fact that most of these transmissions are filled with ATF or some other strange fluid from the factory, when in fact they work and shift better when filled with 5w30 weight motor oil. Basically, the same stuff you run in the engine.

So, how does a guy change the fluid?

When a transmission is being rebuilt, a good modification is to tap the bottom of the housing for a drain plug. This makes it VERY easy to get out all the fluid. Furthermore, with this method, you can attach a neo-magnet or the like to the drain plug and it will collect all those metal particles.

But, of course, the majority of people changing tranny fluid aren't doing it while the transmission is being rebuilt.

So, there's several other methods.

You can pull out an axle. This takes a little time, and is a relatively painful experience for your buttocks. And you still don't get all the fluid out.

You can either suck the fluid out yourself, or have it professionally sucked out. If you take it in, they have some vacuum contraption which will suck it out. If you want to do it at home, you can buy a contraption that looks like a bicycle tire pump, but with a bigger hose, and it work backwards. This method is fairly effective, but requires a little extra coin. If you do take it in, make sure you ask them to refill with 5w30, rather than ATF or Gear Oil.

I changed the fluid in my 525 yesterday. I used a method mentioned by a guy on another site (Turbo Rampage, I believe his screen-name was). Here's what I did and it worked VERY well.

Jack the car up on the drivers side. I used the frame rails right behind the front tire.

Remove the wheel.

Remove the plastic cover with it's 2 10MM bolts that is in the way of you seeing the transmission.

There is a ring around the spot where the axle goes into the housing. To drain the majority of the oil from the transmission, simply remove the 13MM bolt that is the closest to being on the bottom. On my car, this bolt came right out, and bright red fluid started shooting out. I've heard rumors that on some transmissions, this bolt will not come out because of the axle. In this came, you might be best served to pull the axle AND remove the bolt. The bolt is lower than the axle hole, so more fluid should come out.

Now, since this bolt is a seal as well, it's probably a good idea to give it a coating of rtv before you stick it back in.

To get all the fluid out, I found that it was necessary to jack the car up and down in small incriments. At first I believed that just lowering the car down almost to the rotor would get as much as possible, but upon raising the car back up past where I started from, I got even more oil out.

The transmissions should hold a little more than 2 quarts. (2.3 total capacity, I believe)

When it comes time to refill, reinstall that bolt (with RTV), and remove the rubber drain plug that should be slightly forward and slightly up. It should pull right out with your hands or with the help of a flat screwdriver. You want to use a funnel or something to put in about 2 quarts.

Basically, just fill it till it starts coming out of the fill hole.

And that's it. Put the plug back in, put the wheel back in and enjoy!

PS - this project goes well with about 2-3 beers. ;)