Diff & Transfer case fluid selection

AMS Oil severe gear

$30 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 GL-5 or Royal Purple Max gear which is both a GL-4 and GL-5 fluid at the same time. These are my top 2 choices to use in my front and rear differential but the big question is are one or both of them sufficient for the transfer case as well? There is YOUTUBE channel called the Car Care Nut that specializes in Toyota maintenance. The GL-5 rating seems to be adequate for the transfer case but NOT a manual transmission. The manual transmission requires a GL-4 only due to the synchromesh. (Not applicable to me I have an automatic) but as far as the transfer case is concerned the Royal Purple is labeled both for GL-4 and GL-5 and the AMS gear oil is just GL-5. Toyota has a very expensive transfer case fluid that's like $80 a quart but most of what I've read points to the using the same gear oil in the transfer case as the diff.

 

I would not use gl-5 in the transfer case. As far as I know there are brass synchros, so gl-4 it is. Redline has a gl-4 75w which they recommend for TC. Redline Mt-lv.

 

AMS Oil has a GL-4 fluid that looks like it should work for the transfer case.

 

That would be my choice from Amsoil, but it may not meet the "or equivalent" for warranty purposes.

 

The parts guy at a dealer said to use MAG 1 Gear Oil: Synthetic, SAE Grade

$30 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 GL-5 (just changed my front & rear diffs with the same stuff). He said that all they use in all 3 for changes. Was going to change my t-case this weekend with this stuff...

 

No doubt it will work in the TC. Just not what the factory uses or recommends in their manual.

 

Ya I was kind of surprised he mentioned that all 3 use the same oil. I have a couple of qts left over and was just going to use that. Are there long term effects from using GL-5 vs GL-4 since its not factory/manual recommended?

 

That’s what I use. And dino oil for the diffs.

 

I'm no expert, but I know GL-5 "can" potentially damage yellow metals, although most have corrosion inhibitors now to prevent that. Only other issue could be too high of lubricity which could affect synchro mesh and gear engagement.
The manual doesn't actually specify gl-4 in this application. It just says to use their oil or equivalent. Several manufacturers have a recommended replacement in a gl-4 75w.

Edit-. Had "does"... Should have been "doesn't"... Oops.

 

I should of went with my gut feeling on when the parts guy said use the same fluid as the diffs. I knew, but wasn't 100% sure that the T-case was a different fluid. Will be searching for that Redline MT-LV for this weekend. Appreciate the heads up.

 

I went with OEM fluids in the hard to open and impossible to dispense cans. Ebay has the transfercase fluid for about $55 a quart and the diff fluids can be had for around $30 a quart/can at dealers. A little expensive, but you don't have to change them that often and you don't have to wonder what if either.

 

$24 Red Line (50604) MT-LV 70W/75W GL-4 High-Performance Full Synthetic Gear Oil Lubricant for Manual Transmissions & Transaxles - 1 Quart

https://www.amazon.com/dp/B07V1VW32J

So is this the redline fluid to use? The picture is terrible but the description says Red Line 50604 Mt-Lv 70W/75W Gl-4 - Quart.

 

Yes.
Here is their datasheet with the Toyota oil listed:
https://www.redlineoil.com/Content/files/tech/MT-LV_GO_PROD_INFO_2023.pdf

 

Nice, thanks for the info. Going to order 2qt it so it gets here by this weekend.

 

I’ve got this in both diffs and the price is right. Get it by the gallon

 

Sub….

 

The differentials can use any common gear oil that meets specifications (75W-85, GL5) regular or synthetic.

$30 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 is commonly used, there is no cutting edge technology in there, differentials generally aren't fussy.

The transfer case however specifically calls out a single grade 75W "transfer gear oil", a GL rating isn't specified.
You may experience engagement difficulties using 75W-90 in colder weather.

Though YouTube, "the parts guy" and others may recommend alternate lubricants - Toyota recommends the 75W product and it only takes a quart. I prefer to use the recommended product and call it a day.

 

AMD (The Car Care Nut) talks about the front and rear diffs and the transfer case lube in a few videos that he has done and advises GL5

$30 75W-90 Synthetic Gear Lube - 1 Quart (Pack of 2)

75W-90 is fine for all three. He also talks a bit on the subject of the Toyota-specified 75W transfer case oil subject at about: 7:50.

My truck is a 2014, so the expensive OEM/Toyota $85 75w transfer case gear oil is a non-issue for me. The owners manual specifies and 75W-90 GL-4 or GL-5 for the transfer case, and 75W-85 GL-5 for the differentials, I'll likely use Mobil-1 when I do the job this spring.

The manual also specifies GL-4 75W-90 gear oil for the manual transmission.

 

Or you could get the factory spec'd oil and not rely on strangers opinions on the internet? It might help you sleep better at night too haha! Time is money and you're spending time considering something that has already been advised by the manufacturer.

It's a $40k truck, we all know you can afford the correct oil.

Just my two cents... and yes when I do my 30k maintenance in a couple months I'll be "splurging" for factory oil.