How-To: 6-Speed Manual Transmission Oil Change

Does anyone know the part number for the drain/filler plugs for these? Just changed my tranny oil and the filler plug is looking pretty rough... Alternatively, are aftermarket plugs available anywhere?

Edit: Some googling suggests that the drain/filler plug threads are M18x1.5. Can anyone confirm this?

 

THANK YOU SO MUCH! Will be doing this tomorrow with the Transfer case and Front and Rear Diffs. I added your link to my build page. If it hasnt already @tcBob can you sticky this for us Manual guys?

 

I was just about to do a search for this exact topic. Thanks for the write up!

 

for those in need......

GL-4 oil (MT-90)

 

got it today

 

The best a trans can get.

I’ve also mixed this with RL MTL with great results.

 

Ive been running Lucas 85w140 in mine for a while now. I like it more than the redline mt90

 

Yes that is the size. I measured them.

 

Picking up this old thread. I have a 2005 6-speed manual with nearly 200k miles, and the transmission fluid is past due. Is it a bad idea to switch to Redline at this point?

 

I have an 330k mile RA60 2wd. Did an oil swap with MT90 not too long ago. Haven’t had any issues with leaks or grinds.

 

When I bought my X runner used and 4 previous owners had wailed on it I took a chance. It needed new throw out bearing and wasn’t sure if transmission had ever been serviced. The second gear synchro was a little weak and also got occasional grind going into 6th gear. I gambled on changing to Redline MT90 after reading other people’s experience. It took awhile to smooth out but the shifting got better and the grinding went away. I can’t explain it. The only thing is this Redline seemed to be a thinner oil and color. Reminded me of ATF. I was using Valvoline 75-90 before. I did this at 96k miles and I’m thinking about doing it again, now at 145k.

 

Just updated the first post with the latest info on oil specifications.

Update 05-26-2020:
Note about oil choice. I’ve circled back and done some research on this, seems like at some point Toyota clarified the spec for the gear oils. The latest info for the 2nd gens is as follows:

Differentials: 75W-85 GL-5
Manual transmission: 75W-90 GL-4
Transfer case: 75W-90 GL-5

As some point Toyota used to spec GL-4 or 5 for the transmission, this is no longer the case and you should ONLY use GL-4. This would be the redline MT-90. Using GL-5 in the transmission will prematurely wear out the synchros. And using GL-4 in the differentials will prematurely wear out the diffs. The transfer case and differential oils should be the standard GL-5 gear oils that Redline sells

 

So I’m changing the oil in my 2006 six speed today and I glance in the manual and see it says GL4 OR GL5. That caught me off guard because I was always under the impression GL5 with its additives can really mess up your gearbox synchro rings but is good in diffs (high temps).

I’m at 106k miles and this is the first time I’ve had to change it because the original gearbox was changed under warranty at 58k miles.

 

Yup that’s definitely the case. Use GL4. MT-90 is the way to go!

 

Did this again today. I have to say using the gallon jug with the slippery Pete pump is 1000x easier and cleaner. Also found using a 24mm combo wrench is a lot easier than using a socket.

Slippery Pete Fluid Pump for Gallon Bottles and Wide Mouth Quart Bottles - Transfer Gear Oil, Transmission and Differential Fluid, Antifreeze with This 30cc Hand Pump

$17 Slippery Pete Fluid Pump for Gallon Bottles and Wide Mouth Quart Bottles (Not for Standard Quart Bottles) - Transfer Gear Oil, Transmission and Differential Fluid, Antifreeze with This 30cc Hand Pump

https://www.amazon.com/dp/B07DTS8N7P/ref=cm_sw_r_cp_api_i_VZ3cFb1WFH5GH

 

After having fought a inferior pump, installing a short shifter and pulling my trans to replace a clutch from now on I will fill it from the top through the shifter hole. It’s way too easy to get in there. By the time it drains you could have the console out and have the shifter removed. With the console out of the way it’s easy to adjust the slack in the Ebrake while your at it.

 

Is the full level at cold or does it have to be at operating temps?

 

I do it at cold. It really doesnt matter to be quite frank. Several things to note here; 1) the gear oil wont get as hot as ATF so expansion isn't an big of an issue, 2) in truck automatics you have as much as 10-15 quarts of oil that get pretty hot so expansion of the fluid is an issue, 3) much like the oil in your engine, in an auto trans you dont want foaming. ATF is used as both a lubricant as well as hydraulic fluid. Overfilling an auto trans/engine can lead to foaming which causes all sorts of issues and can lead to failure.

So how does this relate to a manual? In self lubricating gear applications like a manual transmission and differential foaming is part of operation. The way things get lubricated is by the fluid getting shot around violently as well as getting carried by the gears. You also cant really "overfill" persay unless you some how manage to pour enough fluid to fully fill the case. A lot of 1st gen taco guys actually "overfill" their 5 speed manuals by about 25% because it shifts better for some reason. As long as your fluid level is at a reasonable level you'll be fine. Cold is fine. Hot is fine. It really doesnt matter. You can do a hot level procedure but you're spending extra time for nothing. Factory service manual just says to fill to the fill plug no mention of checking the fluid level at a specific temperature.

Heres a couple of videos you can skim through to see how the fluid moves around. The one by shell is animated and it gives you a good idea of how it works on principal. The 2nd one shows the mess of oil flowing everywhere normally as these gears move so fast flinging oil all over the place.

https://www.youtube.com/watch?v=Sjw7616YI5c


https://www.youtube.com/watch?v=9-yG3D3JBRs

 

If you drain the tranny, why can’t you just add the recommend 1.9 qts? Is it possible for some old fluid to remain, so if you just add the recommended amount you could overfill?

 

Some old fluid might remain. Nothing to worry about. The only way to overfill our manual transmissions is by removing the shifter and filling up from the top. If you fill from the fill plug on the side of the transmissions it’s not possible to overfill it