Transmission Oil Change

If you're looking for steps to change your w56 transmission gear oil, skip the first 5 paragraphs... Otherwise, keep reading and learn from my own suffering.

The transmission on my '85 4runner is in a bit of trouble. When the clutch isn't depressed, it makes a chuckity chuckity noise. Most likely the Throw Out Bearing is going bad. But the Transmission has also been whirring while driving around. I tried to check the transmission fluid level, and it seemed low. But this is the problem with the W56 manual transmissions: there's no good way to test the gear oil level other than to unscrew the fill plug and stick a finger in the hole and see if you can feel anything. So I do. It doesn't feel like I can feel anything, but there is some oil on my finger... I'm not sure if this is because there is enough fluid or just because it's impossible to get the little finger in the fill hole without getting some fluid on it. I'm an amateur, so who knows. I decide it couldn't hurt to buy some gear oil and just top it off. This is where a serious lack of planning turned my transmission fluid experience into a nightmare.

First, I go to Pep Boys to buy just a quart of gear oil, but once inside the auto shop, I'm overwhelmed with the amount of choice in gear oils. Should I go synthetic? I try to do a quick internet search on my phone, but I don't really get all that much except that the Toyota specs for the W56 transmission is API GL4-5 75W-90 gear oil. So I buy a quart and an extender tubes that screws onto the lid of the quart bottle for easy pouring. I head home and then decide to do a bit of research to see if I should use synthetic or not and if there are any recommendations for additives (cause I also think there is a small leak).

I didn't find much in my research other than to use Red Line MT90 oil, which I didn't because it is too expensive, and I didn't have the time to wait for the online order to arrive. I also realized how dumb it was to buy just a quart of gear oil. Being a new car to me, I had no idea when the last time the transmission fluid was changed, if ever. Why not just drain and fill the transmission with new oil? So I headed back to Pep Boys, exchanged the quart of gear oil for a 4qt jug and purchased a 12qt oil catcher (which I later realized was a stupid choice because the most fluid anywhere in the truck is the engine oil, and that's only 5qts; so I took the 12qt oil catch back and exchanged it for the 6qt = trip #3).

Ready to change the oil, I pull out my wrench set and drop under the truck only to find that I don't have the right size socket. The largest socket I have is 19mm. So I run to Sears (I'm a Craftsman guy) and purchase a 22mm socket (trip #4); when I get back home, I jump under the truck and find the 22mm doesn't fit. I feel like a total idiot at this point. I return to Sears and exchange the 22mm for a 24mm (trip #5). Go home, jump under the truck and find that I only have a 3/4" socket wrench and the 24mm I just purchased is a 1/2". I go back to Sears (trip #6) to see if they sell a 24mm with a 3/4" socket, or a 3/4" - 1/2" converter. They don't. I ponder the purchase of a 1/2" socket wrench, but with the purchase of the gear oil, transmission fluid additive, the oil bucket, the pour spout, and the 24mm socket, the transmission fluid change is running close to $60. Auto shops do a transmission fluid change for around $50...

So, I send an email out to my coworkers and wait until Monday before I get my hands on the proper socket wrench.

Transmission Oil Change Tools

Now I have all the tools, and I'm ready. If you're doing a transmission fluid/gear oil change on your own, here's what you need:

• Gear Oil: 4 quarts (API GL 4; 75W-90)
• 24mm & 17mm wrench 
• Oil drain bucket 
• Hand held pump (or pour spout). 
• Clothes you can throw away afterwards 

Draining Steps:

1. First, drive the truck for 7-10 miles to get the transmission gear oil hot, so it will drain properly.
2. Park the truck on a level surface. Engage emergency break.
3. Place oil drain bucket underneath the drain plug. 
4. Remove fill plug (17mm socket/wrench). 
5. Remove the drain plug (24mm socket/wrench)
6. Allow gear oil to drain. 



fill hole w56 manual transmission

7. Inspect the drain plug for metal debris and clean it. The drain plug is a magnet which allows it to collect metallic particles and slivers to help prevent damage from metal chunks getting in the gears as the transmission naturally wears down. Larger chunks of metal are indicative of internal damage.

The oil that dropped out of my transmission was nasty. Black smudge. The magnetic drain plug had quite a bit of debris and one pea sized chunk of metal which means more repairs in the future. But I'm glad I opted for the complete drain and fill over the single quart spot fill I had first contemplated.

Draining the fluid is the easy part. It's filling the tranny back up that makes the job worth the $50 auto shop charge. The fill plug hole is impossible to get to which makes pouring the gear oil in almost impossible. I did a bit of research online and saw 3 choices to add the oil:

1) rig a hose that you can drop from the engine compartment, basically following the exhaust pipe down to the fill hole. Two problems: rigging the hose requires another trip to a store, and the muffler pipe is hot making maneuvering around it a sure burn.

Option 2) Fill from the top: unscrew the center console in the truck and pour the gear oil in where the shifters normally are. But any mistake and you now have gear oil in the truck.

3) Use a hand pump. Probably the best option with the least amount of work.

However, I opted for option 4) remove front tire and stick pour spout hose through the space between the body and the frame. (I thought I was pretty clever in figuring this method out.)

pour spout between frame and body

So, I screw the drain plug back on, take the front driver's side tire off, fix the pour spot to the additive, slide the pour spout nozzle between the frame and body, crawl under the truck, put the nozzle into the fill hole, and begin to pour. The additive bottle drains without a hitch, and I get smug in my ephemeral success.

Next, I pop the pour spot onto the 4qt jug and maneuver all the parts into place. I begin pouring and all is well, at first. But then the gear oil stops traveling through the pour spout. The 4qt jug is a bit too big, so it doesn't fit into the wheel well as nicely as the small additive bottle did. So, I put a little pressure on the 4qt jug, squeezing it up against the inside wheel well. Again, things go well at first, but after a minute, the oil doesn't seem to be traveling very quickly if at all through the pour spout. So I give the jug a good Herculean push; the pour spout ejects from the jug lid and a gear oil showers me underneath the truck. I'm covered in the carcinogenic stuff. Hair, face, mouth, shirt. I work myself out from underneath the truck and stand there, hunched over while the excess oil drips off my face. Out of control. My wife is nearby, so she hands me a dirty old shirt. I wipe the oil off me best I can, cursing under my breath.

With my wife's help, I eventually get the stupid transmission filled. Once finished, I get inside and shower for at least a half hour. I wash my hair 3 times with dishwasher soap as well as shampoo and scrub my body thoroughly with a brush. It doesn't matter, I can't get the smell off me. My mouth lost a layer of skin, and my throat, a day later still burns a bit.

But what an experience! I got to spend longer than I should have under my truck, and I got a great story out of it. Plus, the lesson is learned. I will use a hand pump in the future, or stick to the smaller quart bottles so there is room in the wheel well for gravity to work for me, not against.

As for the transmission: I noticed an immediate difference. It shifts much smoother and doesn't whir as loud.

Got your own transmission fluid change story or suggestions to improve the process? Share it in the comments.