How-To: 6-Speed Manual Transmission Oil Change

Hello all, I need some help.

If I want to run 75w110 in the rear (because I tow) should I also use it in the front and transfer case? Or, Can I run 75w90 in front and T-case and 75w110 in the rear. All liquid will be coming from Red Line. Sorry if this is a dumb question.

Cheers.

 

You should not run hypoid gear oil in the manual transmission or transfer case. MT-90 is a better choice. You can definitely run lighter hypoid gear oil in the front diff. It will never see the heat that the rear sees. 75-110 is good choice for a rear diff on a Tacoma that tows.

 

Thank you!!

 

Finally changed the tranny fluid in my 2014 4.0L 4x4 and it stunk. Looked really clean though, with minimal metal mud on the drain plug, no chunks or flakes. Both bolts came out super easy. This was a great write up @tamer thank you.

I bought a little pump top off Amazon and it was the most helpful thing ever to fill the MT-90 back in. I don't know how I would have filled it without the pump. It did not fit the Redline bottle, but duct tape is a hell of a drug. Filled the tranny until it leaked out and then a couple more pumps. Let it sit and drain off the excess. Bolts back in and it runs like a champ. The butt-o-meter says it shifts better now, but.... you know how that goes.

If you can turn a wrench you can change your transmission fluid.

 

I just spit coffee all over my screen.

 

So I need to pick up a 1/2" extension do this (4wd), would I need a 6" or 10" extension to clear the axle? Thanks!

 

For all you supercharged 6spd folks... How many miles is everyone with the TRD blower and 6spd waiting to change the tranny fluid?

 

The GM gear oil is probably good stuff, I've never run it so can't say either way. But MT-90 is also GL-4 and is specific for manual transmissions. It doesn't meet API requirements for GL-5 EP because it's those additives that cause the issues for yellow metals (typically activated sulfur that reacts with the phosphorous EP additive to protect steel). GL-4 means it still has the EP of a GL-4, though. If the GM fluid is specific to manuals it's probably a similar GL-4 rating so it doesn't need to meet the EP specifications for GL-5 and can have the higher coefficient of friction necessary to spin the synchros.

You don't want hypoid oil in the transmission but you can in the transfer. Since there's no brass synchros to protect you can use GL-5. When you can use it GL-5 is generally better. I personally have always run the same gear lube in my Toyota transfer cases as my axles,

$29 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 Redline or Catrol Hypoy-C. Hypoid oils aren't of as much benefit in the t-case as the diffs. The t-case in my old truck was all gear driven (ours now are all chain driven) and I figured the higher EP of GL-5 couldn't hurt even though there's no sliding like the ring & pinion to need hypoid oil.

 

So for those who may stumble upon this, some housekeeping info...

I did my first driveline fluid changes w/about 12k on the truck (about 36 months ago).

Rear diff came out dirty and lots of metal 'mud' on the drain plug.
T-case came out much cleaner.
6MT came out pretty clean, a little metal 'mud'.
Front diff came out nasty as the rear, also a little metal 'mud' on the magnet.

At the time, I replaced the factory fluids with Redline all the way around -->

75w-85 for FR & RR diffs

$29 75w-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75w-90 GL5 for T-case
MT-90 (75w-90 GL4) in the 6MT.

I just did another change, 18k later (3 years - I don't get to drive the truck as much as I'd like).

Rear diff came out as dirty as before with metal 'mud' and a couple of small (<1mm) metal flakes.
T-case came out somewhat dirty, but not too bad.
6MT was a filthy pig, lots of metal 'mud', and a few small (<1mm) metal flakes).
Front diff was filthy as the rear, with lots of metal 'mud' but no flakes I could find.

Primary motivation for the short interval, in terms of mileage, was time and hard use (lots of 4-lo on ranch roads, heavy loads, lots of water crossing, etc.)

This time around I replaced with Valvoline non-synth in the following spots:

75w-90 for RR diff
75w-90 for T-case
75w-90 for FR diff
Note: Was low on non-synth and local VatoZone only had Valvoline synthetic, so the FR diff is about 40/60 non-synth + synth
MT-90 for 6MT (only GL4 I could find locally)

My actual 2014 owner's manual calls out 75w-90 everywhere except the RR diff. The online owner's manual (toyota.com site) actually shows 75w-85 for the RR AND FR diffs.

So in theory, I'm going against Toyota recommendations for the diffs.

Also I noticed no objective difference in shifting between the factory 6MT fill and the MT-90. But, like I said, it's GL-4, meets factory spec, and was easy to get my hands on.

 

When I did my 6sp I drained all the oil and then tried the pump I bought. It was defective and I couldn't pump the oil into transmission. It was 6pm Sunday night. No where to buy one. I was freaking out because there was nothing I could do. Totally Fed.

So I had a brilliant idea and grabbed a shampoo pump bottle. Washed it out, filled it with the oil, started pumping, and pumping and pumping. I swear it took that little pump about 2000 pumps to fill the transmission. It was brutal. Needless to say I got it done. My neck, shoulders and arms were so frickin sore the next day.

Moral of the story. Make sure EVErything, even the pump, is good to go before you drain the fluid.

 

Couple of things I've found useful over the years.

First, warm up (not hot, just warm) the bottles of oil. Helps it move a little more easily. That baffles me, personally, because the 2nd number (90) is supposed to be the 'hot' weight, so you'd think cold oil would be easier to pump. It's not and I don't know why. Probably my misunderstanding of the 'hot' vs 'cold' viscosity meanings.

Second, at a local 24 hour drug store like CVS, you may be able to find huge (like 250-500 CC) syringes (no needles) sold for wound cleaning/irrigation. Not a perfect solution, but they help. And you can ream the tip out a little to move oil more quickly.

That said, totally awesome Redneck solution you came up with using a shampoo pump bottle. I raise my Coors to you, sir!

 

That is a good idea! I might buy one just to have anyway! And the situation didn't feel awesome. It was terrible! haha

 

transfer case sychronizer: https://parts.toyota.com/p/Toyota_2...RANSFER-SYNCHRONIZER/63008001/3620935022.html

 

FWIW, ToymoCo specs either a GL-4 or GL-5 for both the manual transmission and the transfer case on the early transmissions but later dropped the GL-5 rating for the transmission, at least for the 6-speed, on later models. For example, my '14 6-speed says only GL-4 in the transmission. But the dual rating has been maintained for the transfer case. I'd like to see what those two syncros in the T case are actually made of.

 

No shit, didn't know that. I'm still getting used to all the little details. I came from a '91 when I bought this truck in 2015. That old truck was a W56/RF1A, so it liked MT-90 in the transmission and the t-case being good old gear driven and manual shift was just gears and bearings.

I just assumed since the book only calls for GL-5 for the t-case that nothing had changed but obviously with the electronics and chain drive it's no longer a simple, dumb gear box.

I'm guessing this is necessary to spin up the front drive when you shift on the fly into 4WD?

ETA: Looking now at the FSM for my 1991 looks like the VF1A t-case on the V6s also have a synchronizer ring so it must be something necessary for the chain driven cases. It's not quite the same thing, though. That was on the input shaft and this gets put on the output shaft. I wonder if it is actually a brass synchromesh now.

 

There are two issues with synchronizers. One is the material, the other is the fact of how they work. Super slick oils, as all gl-5 oils are, do not allow sufficient traction for the synchros to do their job. Given Toyota's performance concerning every aspect of this transmission, I don't trust a word they have to say. Can anyone explain why someone like Toyota didn't know that GL-5 would be a problem in the 6-speed to begin with?? Pretty much everyone else knows.

It's understandable that you wouldn't know since the same misinformation about "no synchros in the T-case" has been repeated on the web a million times. My T-case has seen 140,000 miles now of hard use on MT-90. I use the 2-lo lever almost daily. It shifts like butter, and the oil comes out every 30,000 miles looking clean. Build-up on the magnetic plug is minimal. Most people also don't know that the T-case has an internal oil pump. The screen on the intake of this pump is very fine! If you put additives in your oil, or use an oil with additives, you run the risk of plugging the screen. This can also happen if you don't run a snorkel on the case and submerge it. Once that screen is plugged, you are headed for failure regardless what oil you use. The stories of Redline not performing can almost always be traced to some other cause, but since we never get the whole story, we never know. Very few people who share expert advice have ever actually seen inside this case.

 

@badger, indeed I have not yet seen the inside of my t-case, that's is a fact. It's only got 85k on it. I did rebuild the case on the old truck and then built a 4.7 case with a Marlin gear. So I am highly limited in knowledge to old junk.

FWIW, I didn't say you shouldn't use MT-90 on the t-case I was just under the misunderstanding that it was unnecessary. Next change I'll get a couple of extra quarts and run it in the t-case now, too. Thanks for the correction!

BTW, "lever" to get 2-low? Did you do a FJC case? Jealous. IH8 the t-case dial and not having a neutral shift position.

 

Dave,
Sorry, didn't intend to insinuate you were a Redline skeptic. That was meant as a general comment. Yes, I have an FJ case. I can't imagine life without it. Honestly, if this had not been an option, I would have sold the truck long ago. I have logged many miles with a trailer, and backing a trailer without 2 lo is misery. Now there is also an electronic option for 2-lo in a standard Tacoma case. My biggest issue with the knob was that if you ended up in a bad situation before you shifted to 4wd, you often couldn't get into 4wd. It was sometimes a challenge to shift in on a flat dry road.

 

@badger @DaveInDenver Oh, and even a bigger mystery to me is why did Toy put a big azz magnet in the T case and nothing, nada, zero, zilch in the transmission of the 6-speed??? There is that tiny little thing that is on the end of the drain plug but it gets rendered almost worthless in a short time after a few heat cycles of the transmission. I drilled that out and replaced with a real strong neomagnet. Come on Toyota you make a transmission that holds a paltry 1.9 qt. and put nothing inside to catch detritus?

 

Agree 100%. I'd guess the bigger magnet is to keep the screen clear, but yea, why not put that in the transmission too?? I've been meaning to do the neodymium magnet thing in mine too.