Changing Gear Oil -- Close enough?

[Bean Counter]

As a bean counter I can say, mathematically speaking, the difference of 20 to 30 in say the viscosity weight of your motor oil is a much bigger difference than 80 to 90 in your differentials. So my truck wants 5w30 in the engine and that's what it always gets. Does it matter as much in the gear oil? It isn't as plentiful insofar as supply goes and there's a well priced synthetic 75w90 that hasn't caused my truck to fall apart yet. I put it in last go around, but am wondering if I'd be better off getting to 400,000 miles from 300,000 miles if I stick to the SAE 80w in the front and transfer case and 90w in the rear as I think the specs call for. 75w90 good enough all around or need to be exact?

thank.

[Dan-o]

Tagging.......   because I've always wondered the same thing.

[Magnum_Willys]

Synthetic in engines and transfer case is good.  Stay away from synthetics in differentials.  Mfg's and racers will tell you this.  Synthetic just does not cling or cushion like you need in differentials. 

75w-90w is the same as 90w as soon as it warms to operating temp.

----------------------
"Q23. What kind of oil should be used with an Auburn limited-slip differential/ Auburn ECTED Max differential?
A23. Non-synthetic 80w90 GL-5 oil treated with Auburn Gear friction additive, part #504102 (also known as a friction modifier). See Catalog page 32. Three (3) ounces of additive will treat one quart of oil. GM or Ford limited-slip additive may be used. We do not recommend synthetic oil. Auburn limited-slip additive is packed in every box with the differential."
---------------------------

[Bean Counter]

Thanks Willy.
I'm doing some research and starting to remember things from a few years ago when I last did this and stuff sounds vaguely familiar. According to my back-of-the-napkin maintenance records I used the same gear oil all around and didn't add the friction modifier to the differential. I haven't had any problems in my Tundra in the last few years. Maybe its for people who tow?

[Woodchuck]

Synthetic in engines and transfer case is good.  Stay away from synthetics in differentials.  Mfg's and racers will tell you this.  Synthetic just does not cling or cushion like you need in differentials. 

75w-90w is the same as 90w as soon as it warms to operating temp.

----------------------
"Q23. What kind of oil should be used with an Auburn limited-slip differential/ Auburn ECTED Max differential?
A23. Non-synthetic 80w90 GL-5 oil treated with Auburn Gear friction additive, part #504102 (also known as a friction modifier). See Catalog page 32. Three (3) ounces of additive will treat one quart of oil. GM or Ford limited-slip additive may be used. We do not recommend synthetic oil. Auburn limited-slip additive is packed in every box with the differential."
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Um, I run synthetic in the race car in EVERYTHING. Well except for the water in the radiator  . We break in with conventional and after that it goes synthetic. 
I highly suggest using the manufacturer's spec. Some pretty smart people put that out there for a reason, even if we don't know what that reason is.

[jackelope]

I agree with Woodchuck. They put those specific fluids in for a reason.

[Bean Counter]

Um, I run synthetic in the race car in EVERYTHING. Well except for the water in the radiator  . We break in with conventional and after that it goes synthetic. 
I highly suggest using the manufacturer's spec. Some pretty smart people put that out there for a reason, even if we don't know what that reason is.

Well fine then. I'll use the 80w90. But, they also say to use conventional, not synthetic. 

[Woodchuck]

Um, I run synthetic in the race car in EVERYTHING. Well except for the water in the radiator  . We break in with conventional and after that it goes synthetic. 
I highly suggest using the manufacturer's spec. Some pretty smart people put that out there for a reason, even if we don't know what that reason is.

Well fine then. I'll use the 80w90. But, they also say to use conventional, not synthetic. 

That would be the route I suggest.

[thinkingman]

Synthetic in engines and transfer case is good.  Stay away from synthetics in differentials.  Mfg's and racers will tell you this.  Synthetic just does not cling or cushion like you need in differentials. 

75w-90w is the same as 90w as soon as it warms to operating temp.

----------------------
"Q23. What kind of oil should be used with an Auburn limited-slip differential/ Auburn ECTED Max differential?
A23. Non-synthetic 80w90 GL-5 oil treated with Auburn Gear friction additive, part #504102 (also known as a friction modifier). See Catalog page 32. Three (3) ounces of additive will treat one quart of oil. GM or Ford limited-slip additive may be used. We do not recommend synthetic oil. Auburn limited-slip additive is packed in every box with the differential."
---------------------------

Good advice here.
Use dino oil and buy the TOYOTA friction modifier.

[Woodchuck]

Synthetic in engines and transfer case is good.  Stay away from synthetics in differentials.  Mfg's and racers will tell you this.  Synthetic just does not cling or cushion like you need in differentials. 

75w-90w is the same as 90w as soon as it warms to operating temp.

----------------------
"Q23. What kind of oil should be used with an Auburn limited-slip differential/ Auburn ECTED Max differential?
A23. Non-synthetic 80w90 GL-5 oil treated with Auburn Gear friction additive, part #504102 (also known as a friction modifier). See Catalog page 32. Three (3) ounces of additive will treat one quart of oil. GM or Ford limited-slip additive may be used. We do not recommend synthetic oil. Auburn limited-slip additive is packed in every box with the differential."
---------------------------

Good advice here.
Use dino oil and buy the TOYOTA friction modifier.

Just like the manufacturer of that part suggests. 

[jackelope]

Synthetic in engines and transfer case is good.  Stay away from synthetics in differentials.  Mfg's and racers will tell you this.  Synthetic just does not cling or cushion like you need in differentials. 

75w-90w is the same as 90w as soon as it warms to operating temp.

----------------------
"Q23. What kind of oil should be used with an Auburn limited-slip differential/ Auburn ECTED Max differential?
A23. Non-synthetic 80w90 GL-5 oil treated with Auburn Gear friction additive, part #504102 (also known as a friction modifier). See Catalog page 32. Three (3) ounces of additive will treat one quart of oil. GM or Ford limited-slip additive may be used. We do not recommend synthetic oil. Auburn limited-slip additive is packed in every box with the differential."
---------------------------

Good advice here.
Use dino oil and buy the TOYOTA friction modifier.

Just like the manufacturer of that part suggests. 

[Bean Counter]

Thanks hive mind. Trad gear oil it is.

The rocket scientists and brain surgeons that wrote the owners manual don't have the torque specs in there. But, there's instructions on how to lock the doors.  Time to call Toyota.

[jackelope]

Thanks hive mind. Trad gear oil it is.

The rocket scientists and brain surgeons that wrote the owners manual don't have the torque specs in there. But, there's instructions on how to lock the doors.  Time to call Toyota.

You need a service manual, not an owner's manual. Google is your friend.

[jackelope]

What do you need?
I used my mad rocket science skills to find them online.

[Bofire]

  I get my truck serviced when the book says to and I use the stuff the book says. I also use a dealership for my work.
Carl

[Bean Counter]

What do you need?
I used my mad rocket science skills to find them online.

1st gen Tundra and/or Sequoia. Need to do both. is that what you posted?

Thanks!!!

[jackelope]

What do you need?
I used my mad rocket science skills to find them online.

1st gen Tundra and/or Sequoia. Need to do both. is that what you posted?

Thanks!!!

That was for a 2003 Tundra. Honestly I don't know what gen is what.

[Bean Counter]

That'll work! Here goes nothin'..   

Close eyes + slam trigger! 

[thinkingman]

I just completed my gear oil change.
20 minutes start to finish.
Red Line MT-90 75W90 GL4 seems to be exactly what it wanted.

[Jason]

A week ago I changed the engine oil in my 02 Tundra and accidentally put in 5w20 instead of 5w30, so before I ran up and picked up the right weight oil I called and talked to a tech at my local Toyota dealership and he said I was fine running the lighter oil in the winter..hope this true?

[jackelope]

A week ago I changed the engine oil in my 02 Tundra and accidentally put in 5w20 instead of 5w30, so before I ran up and picked up the right weight oil I called and talked to a tech at my local Toyota dealership and he said I was fine running the lighter oil in the winter..hope this true?

Manufacturer doesn't specify that that is acceptable, but I imagine you're ok, especially in the cold weather.
I wouldn't do it in the summer time/hot weather.

[syoungs]

I could be wrong, but at least in fords, running without the friction modifier is terrible on the limited slip if equipped.

I try to stick to manufacturers guidelines on fluids, race cars might run synthetic in everything, but even running as hard as they do, they don't run as long between rebuilds ( least none of them that I know do)

[Bean Counter]

I bought the friction modifier for this go around. Thanks. However, in 60,000 miles I didn't have any problems with just the synthetic 75w-90 even in this hot desert I live in. But I don't tow or even have a heavy payload hardly ever. Would it be worse to switch back to conventional now that I'm running synthetic?

[syoungs]

I don't know if there's a conclusive answer for that, I would do it.

I know a lot of people say not to change to synthetic if it'd high mileage, cause it'll cause leaks, which I don't buy. If the seals are in good shape, they won't leak. Seals not leaking much, will leak more with synthetic though.

[Bean Counter]

Remember I'm talking about gear oil in the differentials

[syoungs]

Yep. Still seals in there though 

[Rick]

You can switch between conventional and synthetic without issue.

[Rick]

A week ago I changed the engine oil in my 02 Tundra and accidentally put in 5w20 instead of 5w30, so before I ran up and picked up the right weight oil I called and talked to a tech at my local Toyota dealership and he said I was fine running the lighter oil in the winter..hope this true?

You're fine. 5w-30 would likely shear down to a 5w-20 by the end of the oil change interval anyway.

I'd have zero issue running 5w-20 in the summer.

[thinkingman]

Go back to Dino oil with the friction modifier.
You'll be fine.

[Night goat]

synthetic oils  and seals dont get along very well, some seals hold up, but, whenever I switched to synthetic, I started getting leaks, and when they start, they dont stop

might be worth researching what oils you have been using and how the recipes have changed over the years, I know that Delo switched up thier recipe with their 15-40 oil, we stopped using delo at work because it is just too dry of an oil, we switched over to a 76/conoco phillips oil. for all the emmisions regulations, oil isnt what it used to be, since most oil for diesels have gone to a low emission formula, they omit zinc, phosporus, lead, and various other lubrication compounds

gear oil on the other hand, as it is not in a crank case, hasnt changed. I would presume that the lower the opperating temperature of a part the higher the viscosity you would want, which might suggest why the lube in the front diff is thinner than the rear diff to compensate for engine heat.

in a crank case, oil needs to be thin to flow, in a cold gear box, oil needs to be thick to stick and provide static lubrication, as a differential or some gear boxes have the gears partially submerged in lube.

the lighter oil in the winter is correct because it compensates for an ambient temperature diference, and being thinner, and colder outside, it takes less to heat and flow properly, compared to using a light oil in the summer, it would be too thin to properly lubricate, whereas a heavier oil will compensate for summer temperatures and provide correct lubrication.

the US Army did a study on motor oil and concluded that motor oil does not break down or otherwise "go bad", however what makes a motor oil "go bad" is contamination with acids, fine particulate matter such as metal wear, and soot, I recently installed an oil bypass filtration system that is supposed to filter oil so finely, it extends the service interval exponentially, to the extent that the company reccomends sending in oil samlles before doing an oil change, as depending on the level of contamination at a normal service interval, it will dictate 1) what is going on in the engine, and 2) whether or not an oil change is really necessary.

oil is pretty interesting
 

[luckyman]

I've had a lot of breakage do to cold weather and not having lite enough oils in Motors, trans, diff in heavy equipment and pickups. Can think of any hot weather failure do to to thin That I've had. I go by the spec but use the lite side when listed.

[Magnum_Willys]

I just completed my gear oil change.
20 minutes start to finish.
Red Line MT-90 75W90 GL4 seems to be exactly what it wanted.

MT-90 GL4   Thats designed for manual transmissions not differentials ?

[Bean Counter]

synthetic oils  and seals dont get along very well, some seals hold up, but, whenever I switched to synthetic, I started getting leaks, and when they start, they dont stop

might be worth researching what oils you have been using and how the recipes have changed over the years, I know that Delo switched up thier recipe with their 15-40 oil, we stopped using delo at work because it is just too dry of an oil, we switched over to a 76/conoco phillips oil. for all the emmisions regulations, oil isnt what it used to be, since most oil for diesels have gone to a low emission formula, they omit zinc, phosporus, lead, and various other lubrication compounds

gear oil on the other hand, as it is not in a crank case, hasnt changed. I would presume that the lower the opperating temperature of a part the higher the viscosity you would want, which might suggest why the lube in the front diff is thinner than the rear diff to compensate for engine heat.

in a crank case, oil needs to be thin to flow, in a cold gear box, oil needs to be thick to stick and provide static lubrication, as a differential or some gear boxes have the gears partially submerged in lube.

the lighter oil in the winter is correct because it compensates for an ambient temperature diference, and being thinner, and colder outside, it takes less to heat and flow properly, compared to using a light oil in the summer, it would be too thin to properly lubricate, whereas a heavier oil will compensate for summer temperatures and provide correct lubrication.

the US Army did a study on motor oil and concluded that motor oil does not break down or otherwise "go bad", however what makes a motor oil "go bad" is contamination with acids, fine particulate matter such as metal wear, and soot, I recently installed an oil bypass filtration system that is supposed to filter oil so finely, it extends the service interval exponentially, to the extent that the company reccomends sending in oil samlles before doing an oil change, as depending on the level of contamination at a normal service interval, it will dictate 1) what is going on in the engine, and 2) whether or not an oil change is really necessary.

oil is pretty interesting

Night Goat The Oil Man! 

[shadowless_nite]

Use regular gear conventional gear oil 75w90 or 80w90. If it has a lsd use the additive. Your wasting the money on synthetic in a toyota differential. There's plenty of old toyotas out there that have been living with conventional fluids, and short of a lsd the diffs have not changed much.  If you want a picture of the barrel they fill your diffs with at toyota dealer I can send you one, it's nothing fancy.

I work on toyotas for a living and this is getting waaaayyyy over thought. Someone let me know when they seen a toyota differential fail because they put 80/90/75w90/80w90 no friction modifier(non lsd) etc etc. Rarely do the toyota diffs go out and if by chance they do it's almost always from neglect or getting beat on wheeling. The ones that go out just because.... Well it happens about as frequent as any other bad stroke of luck.

[thinkingman]

I just completed my gear oil change.
20 minutes start to finish.
Red Line MT-90 75W90 GL4 seems to be exactly what it wanted.

MT-90 GL4   Thats designed for manual transmissions not differentials ?

Correct
I had run the same gear lube in my box as the diffs and transfer case.
There had always been stiffness in really cold environments until it built some heat.
This stuff is dramatically better and the syncros are so much happier. Shifting is completely different even on startup in 20 degree temps.