Hello all, this may be a weird question but I’m looking to replaced the gear oil in the transfer case of my rig with red line fluid.

Should I be using 75w90 gl5 for hypoid gears or the 75w90ns gl5 without the friction modifier? Any information is appreciated

You can also use their MT-90 same as you are putting in the 5spd. No need to have GL-5 in the transfer case. Then you can deal with the transfer and tranny all at the same time.

But the tcase requires GL5 per the service manual and the trans requires GL4 that’s the dilemma. I may be overthinking this.

This is the part I am thinking of using.

Red Line Synthetic Oil. 75W90 GL-5 Gear Oil

I've used GL-5 conventional for both for years. Transmission has always made a grinding down shift to second only when cold. I've heard nothing but great things about the MT-90 as a GL-4 so that's what I'm switching to this winter. Everything else (transfer, front diff, rear diff) is getting the Lucas heavy duty gear oil. I doubt a GL-5 does any damage to the transmission, but I've just hear so many great things about the Redline.

So don't worry. You aren't the only one over thinking it. For how much we all end up spending on other nonsense throwing a few more dollars at a fluid doesn't seem unreasonable.

This was my Black Friday gift to myself

I'm running Red Line 75w-90 in my transfer case and both differentials. I didn't know Red Line made two different 75w-90 gear oils. Here's a link to what I buy:Amazon.com: Red Line 57905 75W90 GL-5 Gear Oil - 1 Gallon: Automotive

Are you sure about GL5 in the transfer? I think we have been down this road before and we have concluded GL4 or GL5 is OK in the transfer.

Mine has had the same GL4 as the tranny for 6+ years.

The FSM for my '97 says GL-4 AND GL-5 are allowed in BOTH trans and transfer.

I have been running the same Amsoil in both diffs and transfer case for the past 5 years with no issues

I wasn’t aware that they made two types either so now I am confused and don’t want to ruin anything.


Edit: This is what I found when plugging my 4Rs year and trans into the Red Line site.

“
DIFFERENTIAL OIL
75W90 GL-5 GEAR OIL
The go-to gear oil for most differentials.
For use in both front and rear differentials plus transfer case where applicable
For use in transfer case of 4x4 models”

When clicking on this fluid it shows the hypoid version of the 75w90 not the 75w90ns. I assume this means that I am safe to the the regular 75w90 for hypoid gears in the tcase? I wish they didn’t make it so confusing.

Well, if it makes your decision easier, the one I linked does say it has friction modifiers in it. I've been using it in my transfer cases and differentials without issue. Something tells me any 90 weight gear oil is going to be fine for our transfer cases. Before using Redline, I used the conventional and synthetic MasterPro brand that Oreilly's sells. From what I've seen so far, they all meet the spec of what Toyota recommends for our rigs.

That makes me feel a lot better. One of the local forums I posted in also has similar responses. Thanks a lot for the responses to everyone and thank you Tim for all of the work you've put in making these awesome tutorial videos.

I just bought my first 4Runner and I'm getting ready to change out all the fluids. This will be very helpful when choosing the correct Transfer case Oil. Thanks!

Man, these things used to turn into flame wars back in the bad ole days (usenet in the early 1990's). Those of us who went through them a time or two started to realize what was important, and that was:

That you HAVE oil. This is 90% of the battle.
That you have the right Level of oil, and we're approaching 95%
That it gets changed, occasionally. And that brings us to 99%

That last 1% is personal and doesn't Really mean anything. But it's where all the arguing and opinions stem from. Personally, I can't do store brand... logically, I know it's coming from the same bulk distributor as the specialty and smaller name brands, but I just can't do it. So I buy a name I recognize, and then usually just shop by price. Hundreds of motorcycles and a half dozen cars since 1990, covering ~1.4million miles plus 2 decades of experience as a profession motorcycle mechanic and I've yet to see damage due to oil brand.

I definitely remember the old forum days where you couldn't ask a single question or you'd get roasted for two pages straight.

Glad we are past that stage.

Based on this, it seems like whether or not it says hypoid gear oil or friction modifier or not it does not matter. More important being that the correct weight and GL5 or GL4 is there and that the correct amount is used.

Appreciate your input.