Topic: Mobil 1 75w-90 in Transmission?

[blackdiamond]

I want to get some synthetic fluid in my transmission and have plenty of Mobil 1 75w-90 on hand.  I think it's officially a GL-5 oil and the owners manual specs GL-4 or GL-5.  I know that Redline MT-90 is the standard for the best synthetic oil and is GL-4, but am not sure if it's worth the effort to return what I have and order Redline MT-90.

Any experience with synthetic fluids in the transmission other than Redline MT-90?  How good or bad is it?

[slander]

I don't know the answer as everything i read has mentioned that gl-5 is bad for synchros.  While we are talking fluid i would like to add what are the boards thoughts on penzoil synchromesh?  It's speced by mopar for the ax series trans, which as we know is basically the same trans as the r series and is yellow metal safe. 

I am curious to hear the thoughts on mobil 1 as well.

[blackdiamond [OP]]

I don't know the answer as everything i read has mentioned that gl-5 is bad for synchros.

I don't think the GL-5 will cause any damage to synchros, but GL-4 seems to provide a better amount of friction that allows them to work smoother.  I just don't know how much difference to expect.  I honestly have no idea what is currently in the transmission.

[emsvitil]

If it's dual rated GL-4 GL-5 on the bottle you'll be fine.

The additive package for GL-5 use  to attack the yellow metal (brass, bronze) in the synchros.    They've either changed the additive package or added more additives so that doesn't happen anymore.


The only possible problem would be the GL-5 is too slick for the sychros.       If that happens,  take it out and save it for the transfer and diffs.....

[blackdiamond [OP]]

I ordered three quarts of MT-90 and will top off the rest with either conventional that I have or the left over Mobil 1.  I can't imagine the 0.4 quarts making much different overall, certainly not worth the price of another bottle of MT-90.

[blackdiamond [OP]]

I put the Mobil 1 in the duals tonight. I was planning to use the fill hole but after seeing how slowly the oil drained (I assume it was due to the oil flowing through the dual adapter bearings) I took the shifter off the front case and put three quarts in. I will drain off the excess this weekend after it has a chance to flow into the rear case and I have time to let it run for a bit.

[slander]

If it's dual rated GL-4 GL-5 on the bottle you'll be fine.

The additive package for GL-5 use  to attack the yellow metal (brass, bronze) in the synchros.    They've either changed the additive package or added more additives so that doesn't happen anymore.


The only possible problem would be the GL-5 is too slick for the sychros.       If that happens,  take it out and save it for the transfer and diffs.....

Interesting, i would like to hear Aisin's stance on it as there's so much internet hearsay out there on this subject.  I found one thread where a dealer was putting 10W-30 in these transmissions, and other threads saying that the gl-5 was a typo blah blah blah....   

The challenge i have is if i even want to run gl-5 gear lube in the trans, its damn near impossible to find stuff without the limited slip additive in it at the stores.   

As for the dual cases i run full synthetic either mobil 1 or castrol syntec 75-140 and fill up the front case and let it soak through.   

[emsvitil]

Actually the limited slip additive makes the GL-5 less slipperier so the limited slip has some bite.......

I haven't looked for awhile, but in the past I found that the limited slip version of gear oils was HARDER to find.

[slander]

Not anymore, thats all they have on the shelves at my local auto parts stores.  You find the non name brand dino oil stuff without the additive, but i prefer to keep it synthetic in the trans.

[Nation]

Not anymore, thats all they have on the shelves at my local auto parts stores.  You find the non name brand dino oil stuff without the additive, but i prefer to keep it synthetic in the trans.

Yeah, the local auto parts stores have crap for gear oil! No selection.. i told them they need to step it u0 and that I don't wanna buy their store brand oil and they should look into carrying a selection.

[blackdiamond [OP]]

Interesting, i would like to hear Aisin's stance on it as there's so much internet hearsay out there on this subject.  I found one thread where a dealer was putting 10W-30 in these transmissions, and other threads saying that the gl-5 was a typo blah blah blah....   

The challenge i have is if i even want to run gl-5 gear lube in the trans, its damn near impossible to find stuff without the limited slip additive in it at the stores.   

As for the dual cases i run full synthetic either mobil 1 or castrol syntec 75-140 and fill up the front case and let it soak through.   

Putting 10w-30 in a transmission almost sounds criminal. Motor oil and gear oil are not at all the same in formulation.  The pressure loads that rotating gears have require different additives than a combustion engine does. That dealership would be off my list!

When my dual adapter bearing blew up I put a bunch of motor oil in the t-case to get it home the. Had it towed in to the shop for repairs. It was so hot that I just wanted volume.

[slander]

That's what i was thinking!     

[blackdiamond [OP]]

I took the 4Runner for a drive tonight. It was the first trip out with Mobil 1 synthetic in the rear differential and dual transfer cases plus 3 quarts of Redline MT90 in the transmission topped off with conventional. The purpose of the drive was to slosh the oils around and to see if I fixed the minor leak by replacing the rubber boot on the front transfer case shifter. What I noticed was the entire truck feeling more loose/free and the sound is also different.  It seems a difference has been made though that wasn't really the goal.

[SqWADoosh]

I am a Red Line guy myself. I put MT-90 in the Tranny and the Transfer. It shifts so much smoother and gets rid of that cold weather hard shifting in the mornings while the truck is still warming up.

[Prismo]

I have run MT90 since the 90's lol My turbo transmission had 250k on it when we rebuilt it, didn't really need it. All the parts were still in good shape. Both transfer cases have 280,000 on them & are still fine, truck has 380,000 on it these days.

[Blackulua]

mt90 on every toyota r or w transmission I own.The Amsoil manual transmission GL-4 oil has been pretty good in my W50 trans for my 81 corolla.

[toyodaaddict]

Any of you guys experience leaks after putting synthetic in your high mileage engines, trans,etc?

[blackdiamond [OP]]

Any of you guys experience leaks after putting synthetic in your high mileage engines, trans,etc?

Yes, but the leaks stopped with a switch back to conventional. In my 85 synthetic leaked out the back of the valve cover, blend oddly seemed to leak out the front, and conventional stopped it from leaking. No issues with transfer cases or transmission, but both are rebuilds within the last 30k.

[toyodaaddict]

Its good to know that the leaks stopped after going back. Ive been real hesitant to use it in anything but diffs, for fear of getting leaks and having to tear everything apart.
 My dad just picked up a nice low mileage 04 3.4 tacoma to replace his honda and that had me thinking about synthetic again.