Changing the Auto Tranny fluid (turbo & non turbo models)

By Steve Chong

Created : 980501
Last updated: 980519

1) Jack up your car so that it is level. See other "How Someone ..." for suggestions of how to jack up your car.

2) Place a large pan, at least 2' X2' wide under the tranny to catch the oil. Up to 5 litres - 11/4 US gals will come out.

Car up on blocks (note how the car is level. This makes checking the fluid level in the tranny easier) :

Car up on blocks

Car up on blocks

Oil tray :

Oil Tray

3) On turbo models, undo the drain plug ( where the white arrow is in the picture) in the transmission pan with a 19 mm socket, and drain out the oil. I use an old vegetable container out of a refrigerator to catch the oil. After the oil is drained, there will still be about a 0.6 liter (a pint) of oil left in the pan.

There is no drain plug on non turbo models, so go to step 4.

Drain Plug

4) Undo all 18 bolts which hold the transmission pan in place, using a 10 mm socket. I use a socket with a 1/4" drive, so I could get at the bolts more easily. Undo the two oil cooler pipe brackets, also using a 10mm socket, and remove them.

5) Remove the transmission pan, and clean up the pan & the magnet in it. Use lint free cloths in the cleaning process.

Here is the auto tranny with the pan removed :

Auto Tranny with pan removed

Here is the auto tranny oil pan (Shown is the pan for the turbo. You can see the round magnet at left which has been cleaned up) :

Auto Tranny Oil Pan

6) Remove the oil strainer, shown by a white arrow, by undoing the 4 bolts. You will also have to undo a 5th bolt which secures a bracket so the bracket can be swung out to enable removal of the strainer. You'll need a 10mm socket for this.

Oil strainer

Oil strainer removed :

Oil strainer

7) Pull down the strainer, being careful not to lose the O ring seal.

Top view of oil strainer (note the O ring on the strainer pipe) :

Top view of oil strainer

8) Clean up the strainer, washing out iron filings with mineral turpentine. Dry thoroughly.

Prepare for the good or bad news:

A few particles: no need to dip into the piggy bank. Lots of brown chunks: clutch plate disintegration. Overhaul. Lots of steel filings: Clutch plate, brake band, bearing disintegration. Overhaul. Lots of aluminium filings: bushings & cast parts disintegration. Overhaul.

9) Put the O ring back on the strainer and reinstall. The manual recommends putting petroleum jelly on the strainer O ring, but I used AT fluid.

10) Put a new gasket on the oil pan and reinstall. Do not over tighten the bolts.

11) Fill the tranny through the dipstick hole. By using a 12 mm (1/2 inch) outside diameter tube, you will have no problem with trapped air preventing a fill. You will need about 3.5 litres (almost a US gal). Use your favourite brand of Dexron IIE or Dexron III specification fluid. Some IZCC members recommend synthetic oils.

Funnel and tube :

Filling the tranny

Funnel and tube :

Filling the tranny

12) 11) Start the car, put your foot on the brake, and shift from 1-2-D-N-R-P. Gradually put a bit more fluid in until it reaches the correct level on the dipstick. When checking the level, the engine should be running with the shifter in "N".

13) Go for a test drive, an recheck fluid level and check for oil leaks.

14) Repeat this every 2 years or 36,000 miles.


a) keep a sample of the new fluid in a clear glass jar, so you can compare, from time to time, the color & clarity of the new fluid with the fluid in the tranny. The jam jar on the right contains new fluid.

Jar with tranny fluid

b) the pan gaskets for the turbo and non turbo transmissions are different shape- make sure you get the right one!

c) When you change the tranny fluid, you will be changing aproximately half the fluid in the transmission, as you can't get the fluid in the torque converter out without dismantling the tranny. If you are concerned about this, change the fluid again after running a hundred miles. If your 90+ has been regularly maintained, and it has been used under "normal" conditions (ie, not been raced), then I don't think you need to worry about doing this "double change".

In my case, because I had bought a badly maintained Z, I did a "triple change" to get the color and clarity of the oil in the tranny to a level that I was comfortable with. You can see from the photo the difference in color between new fluid and a "double changed" fluid in my tranny. Here I put a green colored X on a white sheet of paper and filled the jar to 1 cm so I could compare the results of fluid changes. You can't even see the X in the left jar! I also kept old samples to work out when I should do my next change.

If you are not doing a fluid change, you can easily get a sample of fluid by inserting a 6 mm (1/4 inch) plastic tube down the dipstick tube and siphoning some oil out.

d) A number of IZCC members have reported early failure of their Auto tranny and have attributed this to failure to change their tranny fluid on a regular basis- recommended every 2 years or 60,000 Km or 36,000 miles.

Mike Kojima " writes:
Date: Fri, 20 Mar 1998 00:16:23 -0600
Subject: RE: <90+> Transmission life

"The weak link to the 300ZX's auto tranny is that it is sensitive to debris such as clutch and Lock up piston friction material in the oil. This stuff plugs up the cooler and starves the rear planetaries and BOOM. It also gets into the valve body and causes problems there.

The transmission itself is a very strong and robust design but you must change the fluid and screen at regular intervals. I do my pathfinders tranny's fluid, which is almost the same as the Z's every 25,000 miles. I do the screen at 50,000 miles.

If you do blow the tranny, you should replace the cooler because it gets full of crap."

e) I found the magnet in the pan was so totally saturated with iron dust that it was no longer able to function, and there was iron dust all over the inner workings of the tranny. The strainer though, had only 4-5 iron particles in it, indicating that nothing was disintegrating too badly.

When I explained my situation to Gord Ehrenlechner , he replied:

"I changed mine at 35,000 km, there were iron particles on the magnet, but nothing one wipe of a towel wouldn't remove. I would describe it as more than a trace, but certainly way less than what you describe"

Happy re-oiling

Steve Chong
May 1998

Back to the Home Page