unhappy with 80w-90 gear oil

[NWMO]

Professor,

This is pretty much the only fluid that meets the criteria for our vehicles. Nobody makes a readily available dino-oil in the right weight while still being a GL-4 rated oil.

Here is what I chose, but as you state, not organic.

https://www.amsoil.com/shop/by-product/ ... be-75w-90/

Chris

[xirdneh]

I tried gl4 once, 6 months later the front differential gears were broken. I have no idea whether or not gl4 had anything to do with it. Not sure if I will try that again

I have a another tranny/differential that has 435,000 miles on it using gl5 and it still shifted just fine.

[The Professor]

I tried gl4 once, 6 months later the front differential gears were broken. I have no idea whether or not gl4 had anything to do with it. Not sure if I will try that again

I have a another tranny/differential that has 435,000 miles on it using gl5 and it still shifted just fine.

Brand, weight, mileage and type of usage on the oil? How many miles were on the transmission?

It's dangerous to throw out isolated incidents like that without appropriate background.

[xirdneh]

Sta-Lube SL24239 API/GL4 85w90 is what i used
tranny/diff had just over 250,000 miles on it
it was probably just a Coincidence
but still "Not sure if I will try that again"

[Petros]

GL 4 is intended for manual trans, and GL-5 for hypoid gear diffs. GL 5 had more Extreme Pressure (EP) adaditives in it. apparently some manufucturers' syncros wear away faster with GL5 gear oil (reacts with the metal and wears about twice as fast).

industry fact sheet says the following:


GL-5 GEAR OILS ARE NOT INTERCHANGEABLE WITH GL-4 GEAR OILS.

* The extreme pressure (EP) additives in most gear oils contain sulfur-phosphorus compounds that can be corrosive to certain “yellow” metal components such as copper and brass synchronizers.

* Always follow your owner’s manual for the correct lubrication recommendation.

[ARCHINSTL]

The OMs for (at least) our '85 and '86 cars state "GL4 or GL5," so ...
Tom M.

[NWMO]

Hey All,

As stated earlier by others, this can seem as subjective as paint color, with no clear right or wrong. Part of the reason I chose NOT TO USE REDLINE products is the following note from their website.

MTL, MT-85 & MT-90 are not for use in differentials with hypoid gears

Petros or others - if I understood correctly, the front differential includes "hypoid gears" on our vehicles, correct?

Maybe other brand gear oils at this weight include use with hypoid gears (as I believe the Amsoil product does), I can't say. But Redline does not recommend it for their products.

Chris

[Petros]

if the problem with GL5 is the syncro alloy reacting with the EP additives, it is possible that toyota formulated their syncros to be compatible with GL5.

With a transaxle assembly that mixes front diff and gear box lubricant, than it is somewhat baffling that the FSM says GL4 is acceptable in the transmission if the GL4 was not intended for hypoid gear pressures. FYI, hypoid gear geometry as used in the ring and pinion puts a high shear stress on the lubricant, with a high rate of lube failure without the extra additives.

As a data point, I have an estimated 300,000 miles on my transmission, and I have always put in GL5 because that is what was available. the syncros feel somewhat slow (especially when cold), but they appear to still work fine (particularly after the gear oil has warmed up).

Last gear oil change I put in some graphite lube additive, presumably to reduce wear.

I am about to install fresh gear oil in the trans (I just changed the clutch), and I found a supplier of GL4 gear oil to install in it. but now I do not know what install. I have both GL4 and GL5, I think I might even have one quart of synthetic gear lube to blend, and a bottle of graphite additive.

I think I want to try the GL4 alone to see if it helps my syncros. But now I do not know.

[spencercat]

Petros: I'm thinking of changing from an STP 80w90 gear oil to something else to eliminate a notchy feeling and difficulty getting into 5th and reverse. Can you update us on your gear oil experience since your comment above? Thanks

[Petros]

yes, I put in the GL4, with one quart of synthetic gear lube (out of 4.1 qt total), and the graphite additive. I have been very happy with it, no problems with syncros or gear clashes, and the syncro hesitation is not even noticeable. I have not noticed the slow syncro operation in sub freezing weather either. but I did not use it much in the mountains last winter since I was driving other cars for that.

Overall it seems like a good mix.

[newplaner]

So, my 83 owners manual says to use GL-5 in the transaxle. Not given the GL-4 as a choice. It also says to use SAE 90 or 80W-90 above 0 degrees F.
But in the rear diff they say to use SAE 90 above 0 degrees F.
I am not the experimenting type with this terc. So, I dont really want to be blending. Does anybody use SAE 90 for both ? If so, what brand?
I am very confused at this point.

[pbtv]

Folks, I think it's fair to say that if your tranny has above 200k miles or even 300k; it's not really accurate to say that 5 vs 4 is the culprit for failed synchros or related woes. It may be a factor, but the longevity of the tranny has more to do with driving style and REALLY whether you change your oil and stop leaks when they occur. Several members have posted about 300k+ tranny's with gl5 and others have posted the same about gl4. I'd say we just settle on what doesn't work for a few members which seams to be Redline brand.

So far no one has posted a higher mileage than xirdneh with 400k+ on gl5.

[teranfirbt]

The front differential design in the T4WD is not as bad on gear oils as most differentials. Since the pinion intersects the ring gear near the centerline of the carrier, instead of way below center like most differentials, the gear teeth don't have near as much sliding action as the unit spins, which is why GL4 is OK for our front diffs. The rear diff definitely needs GL5 since it is built like most differentials that has the pinion axis offset from the carrier axis.

[The Professor]

I finished swapping out the gear oil in my Tercel's transmission and rear axle with 80w/90. The old oil looked to be in pretty good condition, it was a dark amber and didn't smell as awful as black, ancient gear oil. Ditto on the rear axle.

Before, the trans would shift OK, but would nip the gears a little on the 1-2 and 2-3 upshifts. After the fluid swap 3rd gear will grind if you hustle the upshift. It's fine if you shift slowly and smoothly. I drove it a few miles and things didn't seem get any better. I'll have to go for a longer drive to see if higher temps help the shifting, but as for now, I'm considering draining out a quart or so and tossing in a quart of synthetic, as suggested.

Also, does anyone know the name of the engineer who designed this transmission? I have a few choice words for him. If you're familiar with Subarus, they have essentially the same engine/transmission layout as a Tercel. The difference is, the front diff is internal to the transmission case, there is only one drain plug, and, gasp, a dipstick and fill tube!

FHI>TMC on mid-80s transmission design...

Once again I will state that I believe that Redline 75-90 NS is the best lube for the t4wd trans.

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

Cut and paste from the above link:

Improved copper corrosion protection to prolong synchro life

Redline themselves suggest a different fluid for the 6-speed Tercel: MT-90 75W-90 GL-4 gear oil

Offers quicker shifts, perfect synchronizer coefficient of friction
Safe for brass synchros, as it lacks the reactive sulfurs found in most GL-5 oils that cause damage
High performance gear protection and longer synchro life
Eliminates notchy shifting, even when cold


I'm about to order some and will check back in to let everyone know how it does. My main problem at this point is a crunchy 3rd gear syncro that was not present before I did a trans oil change.

I finally got around to changing out the transaxle fluid, since I was already poking around with the neutral return piston. As you can see from my prior posts, I started with some minor balking on upshifts when I originally bought the car. Swapped the fluid with generic 85W-90 dino-based gear oil and while the 1-2 upshift improved, the 2-3 upshift got worse. If I shifted any more quickly than "lazily" I would notice a bit of a grind going into third gear.

After doing some research, emailing different suppliers I settled on Redline MT-90. This is a GL-4 oil, the proper fluid for our transaxles. The reason this is important is that GL-5 oils will adhere to the brass synchros in our cars and as the oil and synchros do their speed-matching-dance, tiny pieces of brass are literally being ripped off the synchros. Modern GL-5s are even worse.

The gear oil I drained from the transaxle a few days ago had been in the car for a few years, but only had a few thousand miles on it. You can imagine my shock and utter disbelief when I saw how much brass dust was suspended in the old gear oil. I'm no talking about some flakes or shimmering tailings at the bottom of the pan, but spread throughout the entire 4.1 quarts, suspended, like a grey/green/gold flaked paint job. THIS is what GL-5 does to our transaxles! (Pics if I remember)

So here we are, transaxle drained, refilled with Redline MT-90 and WOW! This faintly pink fluid completely eliminated the 2-3 upshift grind. In fact, I couldn't get the transaxle to grind AT ALL upshifting or downshifting throughout the gears. I need to pump up the tires and take her up the grade of Snoqualmie Pass to get everything nice and hot before I'll officially sign off on the fluid, but there you have it. A pure, 100% ester-based GL-4 synthetic gear oil that IS NOT "too slippery" for our transaxles.

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

[dlb]

Very interesting. I look forward to trying Redline out myself one day when I find another t4 project. Thanks for the follow up on your experience.