Transmission oil vs Differential oil, 87 Toyota Van 4wd

[SeattleSquatch]

Hi all, first time post!

Recently purchased 87 Van 4wd MT. First project to get my hands dirty: replacing Transmission, Transfer & Differential oils. Comfortable with a wrench but low on knowledge.

Referring to repair manual, Transmission & Transfer (4wd) calls for API GL-4 or GL-5 SAE 75w-90

While Diff calls for "Hypoid gear oil" GL-5 SAE 90 (for above 0F).

After reading posts on synthetic vs Dino (not sure what is in the van now):

http://www.toyotavantech.com/forum/showthread.php?223-Clutch-Replacement


https://www.toyotavantech.com/forum/showthread.php?2874-Manual-shift-issue-hard-to-get-into-gear/page2&highlight=Synthetic


https://www.toyotavantech.com/forum/showthread.php?5936-Toyota-Van-Lubricant-and-Fluid-Specifications&highlight=Synthetic


I'm leaning towards the Royal Purple synthetic gear oil 75w-90 for Transmission & Transfer since as Timsrv pointed out:
It is non-corrosive to soft yellow metals (brass, bronze, copper, etc.) and synchronizer safe

But they don't seem to sell a straight SAE 90 Hypoid oil so curious what I should use for the Differential?

On Reddit I was reading
GL-4 is for synchronized transmissions, while GL-5 is for differentials. GL-4/GL-5 is really GL-5 and should not be used in transmissions If true, I feel like I shouldn't just use the same oil across all 3 but not sure?

Also for all these jobs manual recommends a new gasket which I'm sure can't be found ... is the gasket usually unnecessary or do people use the gasket goo for this type of project?

Thanks!

[SeattleSquatch]

I wanted to learn more about Gear Oils and here is some research in case anybody's interested:

Previously I was leaning toward Royal Purple synthetic gear oil 75w-90 for Transmission & Transfer but after further research I'm feeling less inclined to use it.

Attached is a study sponsored by Amsoil Drivetrain Division compared their product against 13 other leading gear oils on the market. It delves deep into all of the testing methods by which the gear lubes are evaluated [American Society for Testing and Materials (ASTM) procedures, Society of Automotive Engineers (SAE) J306 requirements and Federal Test Method Standards]. I like how it's written as they describe why each test is important in a way that's easy enough to understand. Since Amsoil published the findings, I suppose it could be biased but they used independent laboratories and they provide some compelling evidence as to why their formula is considered so well-balanced.

The tests were done in 2007, so I'm unsure if the formulas have changed any with Royal Purple, but at the time, RP ranked poorly across the board on most all of the tests in comparison to the 13 other brands. Particularly interesting findings can be found in the Viscosity Index section:


Royal Purple was the only gear lube to fail both the initial viscosity requirements and the shear stability requirements. It started out too thick and ended up too thin.

And in the "Low-Temperature Viscosity" section:

Royal Purple Max-Gear, having also failed the Shear Stability Test, was the only gear lube to fail every parameter of the SAE J306 requirements.


Most interesting to me was the Copper Corrosion Test (pg 16) which tests the different oils and how it reacts to soft metals. Although Royal Purple states on the bottle "It is non-corrosive to soft yellow metals (brass, bronze, copper, etc.)", this study's findings were that Royal Purple was 1 of 3 oils that failed to meet API GL-5 requirements and was ranked 2nd worst overall in this category.

Pg 19 summarizes the rankings of each of the 14 oils across 17 categories and tests.

Well worth the read for anybody interested in learning more about gear oils and how they're evaluated.

I also liked this YouTube video that conducts a few of theses tests side-by-side comparing Amsoil to Royal Purple: https://youtu.be/E2zS8MyvJxU

Here's the link to where I originally found the attached study: http://www.syntheticwarehouse.com/brochures/g2457_gearlube_study.pdf

Anybody been using Royal Purple? Like it or dislike it?

[SeattleSquatch]

Asking AMSOIL direct:


Is 75w-90 recommended to be used in our older 1987 Toyota Vans with synchro manual transmissions? The manufacturer's repair manual for these vehicles indicates that the manual transmission and transfer case should use GL-4 OR GL-5 75w-90. Your website instructs that it is safe to use in GL-5 applications but I've been told that it may not be recommended for manual transmissions designed for GL-4. Since our repair manual shows both GL-4 and GL-5, and we know that these old syncrhos have some plastic or soft metal parts that can be broken down by some synthetics, is it considered safe to use Severe Gear 75w-90 in the Manual Transmission and Transfer Case in 4wd 1987 Toyota Vans? Also, our specs for the differential call for SAE 90. Do you recommend the Severe Gear 75w-90 or 80w-90 gear oils be used in the differentials for this same vehicle?

And for complete clarity, do I understand that you are saying that the SevereGear 75w-90 gear oil is not harmful to the manual synchro transmissions or should I use something like the synchromesh transmission fluid 5w-30 in the 1987 Toyota Van 4wd?

AMSOIL technical services Response:


The Severe Gear 75W-90 is suitable to use in applications that call for API GL-3 through GL-5, and will not be harmful to yellow metals. This information is printed in our technical data sheet for the Severe Gear gear oils.

For this model Toyota Van, the manual transmission calls for an API GL-5 SAE 75W-90 gear oil. The Severe Gear 75W-90 would be the correct lubricant to use. The AMSOIL Synchromesh Manual Transmission Fluid would not be the correct oil to use in the manual transmission for this Toyota. You are correct that the Severe Gear 75W-90 will not harm yellow metals. The Severe Gear 75W-90 is the correct viscosity to use in place of the mono-grade SAE 90 gear oils.

So in the end, feeling pretty comfortable using Amsoil SevereGear 75w-90 for all three: Transmission, Transfer and Differential :redvan::bluevan::silvervan:

-Steve

[flinters17]

Did you end up changing the fluid with Amsoil? I'm planning to do the same job in a week or 2 and was going down the same path, unsure of which fluid to use.

[jimijuma]

This is what I use for all of my manual transmissions on my classic Toyota's:

https://www.amazon.com/gp/product/B002INX20C/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Its a GL-4, which works nicely with brass synchros. I haven't had any issues. For the diffs and transfer case I just use a synthetic GL-5 75W-90.

[flinters17]

Do you happen to know what size crush washer to use? I'm assuming it's the same for the front and rear diff, transfer case, and transmission since it's a 24 mm head for all of them. Would prefer to buy them locally vs shipping them if possible.

EDIT: Editing my reply since I was able to track down some and they appear to be the right ones. For the transmission and transfer case, it's PN 90430-18008. For the front and rear differential, it's PN 12157-10010. I believe the transmission/transfer case ones are 24 mm OD, 18 mm ID. The differential ones I am not sure but will measure and edit this post once I get them in.

[SeattleSquatch]

Did you end up changing the fluid with Amsoil? I'm planning to do the same job in a week or 2 and was going down the same path, unsure of which fluid to use.

Hey there, yeah I did end up using the Amsoil Severe Gear. I had to call around to 5 or 6 NAPA's in the area to find one that stocked it without special order. After all the research felt very comfortable using the same grade for transmission, transfer and diffs.

Only difficult spot to get to was the front differential filler hole. Recommend taking off three bolts for a shield you'll find down there: made it a bit easier to get a a socket in with two or three flexible knuckles and some extensions. Everything else was pretty easy and accessible.

I meant to write down the gasket info but looks like I forgot to. If I find, I'll post back

[flinters17]

Yes that front diff is a PITA. I decided to save it for when I have more motivation haha.

I changed my transmission oil with redline MT-90 this weekend and HOLY CRAP did it make a huge difference. I was getting rough shifting into 2nd gear and trouble getting into reverse, but as soon as I put the new gear oil in it was like driving a completely different vehicle. Not sure how it will hold up long term but if you ever run into any issues with the Amsoil, the Redline seems to be as good as advertised. A bit pricey but, oil is cheap compared to new parts I guess.

[Jonny]

I'm one of those traitors with a Previa ('91 M/T), but I came across this thread and thought I'd add my experience, such as it is.

Many years ago, before I cared/thought too much about what I was doing when servicing vehicles I replaced my manual transmission oil with some Castrol 80W90 GL5 instead of the recommended 75W90 GL4, because it was the closest thing available at the first store I went to. It seemed to work fine in California, but when I moved to a cold climate it was close to impossible getting into 2nd gear without grinding when the oil was cold.

As a cheap test as to whether the oil viscosity of the 80W90 was the problem I filled the tranny with 10W30 dino motor oil, just for, well, a quick test. The gearbox was so smooth with the motor oil that I left it in there for 2 winters and 20,000 miles of trouble free shifting.

Eventually I figured I'd better change it to the proper specification oil so I put in the Redline 75W90 synthetic oil. The problem shifting came back, nothing like it was with the 80W90, but on cold mornings I have to change into 2nd at under 10mph, or double clutch, or both.

The 10W30 mineral motor oil cured all the problems from a seat-of-the-pants feel perspective and I'll be tempted to go back that route when this Redline needs changing.