Can I use 80w90 in my diffs/tcase?

A friend that owns a shop that service's most all vehicles warned me to use only the toyota transfer case fluid. Doesn't matter as much about the differentials longest its a synthetic of the same weight toyota recommends.

 

fuck.

 

I was told it has to do mostly with 4wd use in the wintertime. If you use other fluids other than toyota, the truck won't readily shift into the 4wd modes when needed possibly resulting in damage to the electronic actuator system.

 

Well it’s a warm country (lebanon) so hopefully they helps. I’ll try to get better oil soon.

 

That would make sense. I'll stick to Redline as well. Have you tried their MT90 in your MT? I did on my 2016 6MT and was surprised at the noticeable difference. especially downshifting 2nd to 1st. I am going to put it in my 2020 6MT in a couple thousand kms when my oil change is due.

 

Yeah, I like to use half MTL and half MT90

 

Redline makes good stuff. As does Lucas and whether they are partnered up or not they know what they are talking about when it comes to this stuff. They told me on the phone its more the viscosity being too low for maintained lubrication and heat transfer. They also recommend shorter change intervals than most factory services call for if you want to keep your differential prime. He said that most manufacturers are running the thinner oils in order to boost fuel economy numbers, not longevity. Hypoid gear technology hasn't changed much in the 60 years or so. I can sacrifice the .5 mpg to keep it on the road longer. Here's the other article they published that's not specific to clamshell that talks about the oils and there's lot of tests out there to back it up if you feel like some light reading.

https://eastcoastgearsupply.com/files/PDF Files/ecgs-gear-oil-recommendation1.pdf

 

Funny you mention MT90, I tried it in my 1st gen 5 speed and had the opposite experience. It did great in everything else I've ran it in so I was a little puzzled to say the least. Apparently the older r150s require a gl4 oil as the gl5 has too much phosphorous in it and reacts with synchros causing premature wear. The mt90 is GL4 but synthetic, switched to el cheapo sta lube gl4 conventional and it was butter made zero sense lol.

 

80W90 is fine in front/rear diffs for standard service.

If you're doing a lot of towing/hauling I would put 75W140 in the rear.

 

Always amazes me how different fluids can have such differing results.

 

Regular oil with an additive makes sense if you change it a lot. 140w if you tow through a desert or have an oddball tire size that outs stress on it maybe.

 

Yes, you can use that w/o issue in the Middle East.

 

thanks. In all 3 ?

 

Diffs, yes. T-case might be a little happier with something a little lighter on the cold side.

 

I have run 80W90 in the tcase for years without issue.

 

Redline makes an equivalent to the expensive Toyota T-case oil (1/3 the price on ebay). It has the same low friction requirements and is a trusted brand.
Red Line Synthetic Oil. MT-LV 70W/75W GL-4 Gear Oil (redlineoil.com)

They also make the factory recommended 75-85W GL-5 gear oil for the front and rear diffs that I just put it in my 3rd gen. I ran Redline diff and manual transmission oil in my 1st gen for years.

 

I use amzoil in transfer case no problems here in washington state

 

75W-85 will have very similar viscosity than a

$28 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 when ambiant temperature is cold. This what the stands for, Winter. So both grades behave as a 75W when cold. So it’s a bit odd to read posts here stating that a 75W-90 in TC will cause hard 4x4 shift until it’s warm.

At warmer temperature, a 75W-90 will be very slightly more viscous than a 75W-85, but at any rate...a warm 75W-90 will always be much less viscous than a cold 75W-85 !!!

So I see no problem using a 75W-90 to repace a 75W-85. Certainly not about cold shifting, since both behave the same way when cold.

 

I was under the impression that the 3rd gen T-Case calls for a straight 75. I went through all the research when I did my gears (I like to keep the T-Case and diffs on the same service interval) and Ravenol was recommended as a good OE alternative. I have it in my truck now and it has been great:

RAVENOL J1C1003 MTF-3 SAE 75W Full Synthetic Gear Oil - 1 Liter for Manual Transmissions, Differentials & Transfer Cases

https://www.amazon.com/Ravenol-J1C1003-Manual-Transmission-Fluid/dp/B00QPCL7ZE?th=1

Don't forget to replace all of the

$12 GENUINE TOYOTA GASKET KIT FOR TRANSFER AND DIFFERENTIAL SERVICE

gaskets.

 

Sir, you are absolutely right, at least for the 2021 (not sure it applies to all 3rd gen year models). The 2021 t-case calls for a straight cold grade 75W. I wonder why? No warm grade means that you have no idea what the fluid viscosity looks like when warn. So it means that cold viscosity is the main concern in this t-case. Interesting