Transmission Oil vs Diff. Oil vs Transfer Case oil?

Hey guys,
I’m pretty new here so I hope this is in the right location. I have a 2015 2.7 4x4 5 speed and I’m wondering if I can use the same oil for the tranny, tc and front and rear diffs. I was looking to buy a gallon jug of the Redline MT90 and wanted to see what your guys opinions were before pulling the trigger.

 

ATF WS for the tranny, 80w-90 in rear diff, and

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

75w-90 for the front diff and T Case.

 

MT90 is great in the transmission. It's basically just GL4 75W-90 gear oil so I guess it would work acceptably in the t-case.

Edit to add:
From their website.

https://www.redlineoil.com/mt-90-75w90-gl-4-gear-oil

The owner's manual says to use GL5 hypoid gear oil in the non-limited slip diffs. So use regular GL5 Redline 75W-90 or whatever else you like.

 

Transmission fluid (oil) is different.....I use Mobil1 75-90 for F & R diff and transfer case.

 

ATF WS is for the 5 speed automatic transmission, I was assuming since he's looking at MT90 he's talking about a 5 speed stick. You wouldn't want to use ATF in a manual.

 

It is a manual transmission. I have the 30k service write up that was posted here saved so I know the steps. I just didn’t know which specific oils/brands were preferred. I’d rather do it all myself just because cost/experience wise. I’ve only ever done oil change and basic maintenance before lol.

 

Well if we go into brands.... i perfer valvoline. I am a valvoline nut after ASE tech school. Mobile is pretty good to. Stay away from pennzoil and QS. People say they use better base oils now but the school got free pennzoil and its what we used there (it was free). The weird varnish it would put on a rebuilt motor in about 30 mins of test running was just weird.

 

MT90 is a GL-4 75w90 fluid specifically for the transmission, don't want to use that in the diffs or t-case. They make a GL-5 75w90 gear oil for the rest. At least that's how it is for 1st gens, check your manual and it will tell you when and where to use GL-4 oil versus GL-5.

And for god's sakes, don't put auto trans fluid in your manual transmission, lol.

 

use the correct lubes !!!!!!!

 

So i went to advanced to look at some lubes and the guy recommended Lucas sae 75-90 for the trans and t case. It doesn’t say if it is gl-5 or gl-4 though it just says that it “exceeds service level”. Is that fine to put in?

Edit. Per my manual it says to use sae 75-90 gl4 for the trans and 75-90 gl-5 for the t case.

 

In this case exceeds is not what you want. From the API's perspective GL-5 does exceed GL-4 in every measurement they use, viscosity, break-down, wear life, shear resistance, etc. But to do it the formulation is different. It happens that what's good for steel and iron gears in this case isn't good usually for yellow metals, which means brass, bronze, copper.

This comes into play in your transmission because the synchromesh collars are made from brass. These are the devices in the gear train that synchronize the gear speeds so that when you up and down shift the next up/down gear is spinning at the same speed as you the one you're currently using and thus no grinding.

To get the pressure performance in the various oils they had to add phosphorous sulfur that reacts on the steel to create a sacrificial wear layer. This coating occurs with pressure and heat and it slowly wears away leaving the steel under relatively unharmed.

It does the same thing to brass but the problem is the underlaying metal is weaker than the coating, so rather than peeling off the metal a thin layer of brass is taken with the coating. Imagine tape on a cardboard box when you peel it off. So you actually accelerate the wear on brass rather than protecting it.

GL-4 isn't specifically for transmissions, though, none of the API specs are that detailed. But generic GL-4 formulations are safer for yellow metals because they contain significantly less of the additive and it's reaction is weaker, so the wear to yellow metals is decreased.

BTW, reading the spec sheets, in the case of Redline's MT oils they go a step further than only meeting GL-4 specs instead of GL-5 but they are designed with transmissions in mind so they don't use reactive sulfur at all (I assume all the sulfur is buffered). This is probably why it's not recommended for hypoid diffs, since it wouldn't create the wear layer that it's supposed to in diff conditions.

You can get any gear oil in GL-4 or GL-5 that would be safe by using buffered sulfur, but it's difficult to find. I've personally never seen it but then again I don't look that hard either. I think it's something you may find in farm stores for tractors, perhaps.

 

Don't avoid Pennzoil. They switched to using a natural gas derived synthetic base oil a couple of years ago in their synthetic line up. It's the only true synthetic oil left on the market, and it shows in testing. @chris4x4 did some oil tests on their motor oil and it showed after a few k of use to be an oil that held it's characteristics really well compared to other synthetics.

I can't comment on their conventional lineup but I have no idea why you'd want to put a conventional style oil in the transfer case or differential other than to save money in the short term.

I'm running all Amsoil in my powertrain right now, but that's just because my buddies a dealer and I got it for less than Napa was selling Pennzoil synthetic and Valvoline Synthetic off the shelf. Similar to above Amsoil claims to go above standard but I think most of that sort of shit is just advertising from boutique oil companies since they can't back it up in independent testing most of the time. In the engine I always use Pennzoil Platinum because of the superior base oil and the testing numbers it's put up on bobistheoilguy.

 

Wow, @DaveInDenver and @Sterdog! You guys have been super helpful in all the information you have provided!

 

Just signed up and bumping this thread.

I've only owned tacoma manual trans, I've used a half half mix of Redline MTL and MT90 in the trans which are GL4 and not as much sulfur, they won't mess up the syncros. I'm aware plenty of owners use GL5 75W90 mobil1 or similar in the manual trans, I wouldn't especially after reading of multiple accounts of owners replacing syncros in their 1st gen tacomas.

For both diffs and tcase I use Redline 75W90 GL5 gear oil. Just switched out everything in my 2017 at 5k miles including M1 0W20 in engine.

I'm a huge advocate of full synthetic oils. My friend just sold his 1st gen tacoma at 440,000 miles and his other friend who is a courier has 650,000 miles on his 1996 tacoma and still his daily driver, he says he wants to get to a million miles, but it'll rust out before then. They use all synthetic oil and gear oil and never had engine or transmissions torn apart besides replacing the usual clutch (plus main seal while at it), tbelts and water pumps.

 

Redline user here- Highly recommend getting the good stuff for the diffs and x-case, tranny. I had a underpowered Jeep with a 4cyl. After the lube change- the shifter was smoother, it would rev quicker through the gears, and I picked up 3 mph on the top end. Since I was tracking every mod I did to the Jeep - started at 57 MPH and when I was done with all the mods it would do 74 MPH - LOL- Synthetic took it from 71 to 74mph. Similar experience with my Miata on the shifting. the Toyota was less noticeable but it is supercharged so a reduction in friction is not nearly as noticeable. I will say I have a lift, E load tires and the super charger and still get about 18.5 MPH mixed driving. I can relay a conversation I had with a Dyno shop owner at a SCCA event I was at- his claim that he was surprised by seeing a gain on the dyno when a customer did a complete change of fluids on vehicle with Redline. So it is good stuff for sure.

 

MT-90 has worked great for me in both trans and transfer.