What oil to use?

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This is for a 1991 4Runner V6 5speed 4x4.

I want to replace all the oil in my 4Runner (engine, transmission, transfer case and diffs). I see that the service manual asks for 75W90 oil and says GL3, GL4 and GL5 all work. Which one is the best to go with? I've heard that GL5 can eat brass synchros.

Would this work:

AMSOIL Severe Gear® 75W-90

?

Also, would that gear lube work in the transmission, diffs and transfer case?

There's also this:

AMSOIL Manual Transmission & Transaxle Gear Lube 75W-90

Not sure exactly what to use, and it doesn't have to be Amsoil. Is there any recommended oil for 4Runners?
 
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Yup, stay away from GL5s in the transmission. They're supposed to be backwards compatible, but they definitely aren't in our application. There's not many actual GL4 oils left out there, and I think they're all synthetics - I use Redline MT90 in the transmission and swear by it. Royal Purple GL4 appears to work well too. The diffs and engine and tcase all get whatever's cheap, they're not nearly as picky. I think clean oil and lubes are generally more important than fancy expensive oils, but the transmission is one place where it really matters.

Also, this is just my opinion, but I won't touch AMSOIL until they move away from their pyramid scheme distribution model. They could have the best oil in the world, but until I see it on the shelf at NAPA I won't use it.
 
KidVermicious said:
Yup, stay away from GL5s in the transmission. They're supposed to be backwards compatible, but they definitely aren't in our application. There's not many actual GL4 oils left out there, and I think they're all synthetics - I use Redline MT90 in the transmission and swear by it. Royal Purple GL4 appears to work well too. The diffs and engine and tcase all get whatever's cheap, they're not nearly as picky. I think clean oil and lubes are generally more important than fancy expensive oils, but the transmission is one place where it really matters.

Also, this is just my opinion, but I won't touch AMSOIL until they move away from their pyramid scheme distribution model. They could have the best oil in the world, but until I see it on the shelf at NAPA I won't use it.
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Thanks a lot for the information. I think I used GL4 in my other car's transmission and GL5 in the diff. Either way I know it was different fluid in each one so I wanted to make sure before I replaced the oil in the 4Runner.

I found a place to get Redline MT90 GL4 locally so looks like I'm all set. I'll probably go with Mobil 1 for the rest of the oils.


One other question: the work service manual says to put in 80w90 in the rear differential. Does it matter if I go with 75w90? The operating temp viscosity is the same for both so I figure it doesn't really matter.
 
One last question (I think): how can I tell if I have the automatic differential disconnect? I think I have it because it looks like I can't change anything manually on the front hubs but I'm not completely sure.

The manual says you need different amounts of oil depending on if you have the ADD or not. Either way it shouldn't matter since you fill the diff until the oil reaches the fill plug, correct?

Thanks for the help.
 
Personally I am a fan of Royal Purple. My tranny shifts like butter. :eyebrows: It's not cheap though, Around $22 a quart.
 
I was at a red light next to a crotch rocket this morning, when it turned green i punched it, speed shifting threw the gears super quick, the crotch rocket didn't know i was drag racing. im happy with the GM syncromesh
 
I swear, some of you guys spend more money on oil then you probably paid for the truck! :lmao:

When I flushed my tranny, I think it took somewhere around 3.5 to 4 gallons of atf to do it. Just get the correct rating and be done with it. Most of these trucks have 20+ years of whatever the PO has been maintaining them with. $20 per quart liquid magic ain't turning the clock back.
 
crash813 said:
I swear, some of you guys spend more money on oil then you probably paid for the truck! :lmao:

When I flushed my tranny, I think it took somewhere around 3.5 to 4 gallons of atf to do it. Just get the correct rating and be done with it. Most of these trucks have 20+ years of whatever the PO has been maintaining them with. $20 per quart liquid magic ain't turning the clock back.
Click to expand...

Who's talking ATF? Get out of here with yer automatic sillyness, this is a 5 speed thread. :flipoff:

The w56 does not like modern GL5 gear oils at all, something about the synchros. I ran GL5 before I knew any better, but switching to GL4 was a night and day difference. No more struggling to get it into gear, no more notchy feeling as I shifted, it really makes a difference. Considering how often I'll need to change the gear oil in the trans, I think it's money well invested.
 
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