switching to synthetic gear oil at 100k?

M

Mr. Baseball

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I have read several threads in regard to using synthetic gear oils. I understand newer T4R's come factory filled with synthetics, I believe starting around '08 or so. I have an '04 4Runner with almost 100k miles and dealer said conventional only. There is a TSB stating front and rear differentials can use 75w85 synthetic gear oil in '03 to '08 Runners. Not sure about transfer case. Dealer strongly advised against switching as I am second owner and don't know what previous history is exactly.

I would really appreciate advice and experiences on switching to synthetic gear oils in differentials and transfer case at "high" mileage. I have a 2004 4Runner Limited AWD 5 speed auto with 4.7 liter V8.

Thank you for your advise, experiences, and suggestions.
 
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I switched mine to m-1 synthetic at 100k - I'm the second owner, no history, and no issues to date. Drives great.
 
Mr. Baseball said:
I have read several threads in regard to using synthetic gear oils. I understand newer T4R's come factory filled with synthetics, I believe starting around '08 or so. I have an '04 4Runner with almost 100k miles and dealer said conventional only. There is a TSB stating front and rear differentials can use 75w85 synthetic gear oil in '03 to '08 Runners. Not sure about transfer case. Dealer strongly advised against switching as I am second owner and don't know what previous history is exactly.

I would really appreciate advice and experiences on switching to synthetic gear oils in differentials and transfer case at "high" mileage. I have a 2004 4Runner Limited AWD 5 speed auto with 4.7 liter V8.

Thank you for your advise, experiences, and suggestions.
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My opinion is to not switch at all.

As I have noted before, many huge axle makers such as Dana including aftermarket axle makers in the offroad world have recommended NOT to use syn oils in gear sets.

We're not talking about an engine here...with oil, gasoline, coolant, lots of moving parts and pieces...we're talking about a stone age simple gear set. It does not need fancy $20/quart oil. It just needs to stay cool. And, in fact, those axle manufacturers have stated that synthetic oils have been proven to protect gear sets LESS than conventional oil due to their thinner and more "slippery" properties. Syn oils actually allow more friction in a gear set...and while the oil may last longer than a convention oil would...the gearset it's protecting won't. Syn. oil doesn't transfer heat like conventional, and the gearset is oil cooled. Syn. is also more prone to running off the bearings which can shorten their life.

I use the cheapest gear oil Walmart has on the shelf...usually $3/quart.
 
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Thank you everyone for experiences and advice. Of course I want to maintain my Runner best I can but I also want to save money. I paid $220.00 for dealer to service all 3.

Even with M1 and new crush washers I can do for about $80. I really appreciate WXman's explanation. The dealer told me they used conventional gear oil and when I do next service it would only cost about half or even less using conventional gear oils over synthetics.

Manual says 80w90 gl-5 for front and rear, easy to find (I don't have limited slip). Is the Valvoline High Performance 75w90 ok for transfer case? It's the only conventional 75w90 gl-5 I can find. Thanks again. One last question, if I stay conventional should OCI be less than every 30k? I don't tow and don't off road, wife's Runner truthfully. Much appreciated.
 
WXman said:
My opinion is to not switch at all.

As I have noted before, many huge axle makers such as Dana including aftermarket axle makers in the offroad world have recommended NOT to use syn oils in gear sets.

We're not talking about an engine here...with oil, gasoline, coolant, lots of moving parts and pieces...we're talking about a stone age simple gear set. It does not need fancy $20/quart oil. It just needs to stay cool. And, in fact, those axle manufacturers have stated that synthetic oils have been proven to protect gear sets LESS than conventional oil due to their thinner and more "slippery" properties. Syn oils actually allow more friction in a gear set...and while the oil may last longer than a convention oil would...the gearset it's protecting won't. Syn. oil doesn't transfer heat like conventional, and the gearset is oil cooled. Syn. is also more prone to running off the bearings which can shorten their life.

I use the cheapest gear oil Walmart has on the shelf...usually $3/quart.
Click to expand...

I'd be interested to read the articles relating to this. I chose Amsoil's Synthetic gear oil specifically because my research showed modern synthetic oils are much better designed and produced than older oils were. They tend to provide better properties than older whale oil and Amsoil says under normal driving conditions their oil should last upwards of 500k (though I'mma switch mine out around 100~200k) as for the "slippery" comment, I think it depends on the oil. A lot of differentials need LSD additives to protect the gears and it also relates to an issue present with modern oils in older engines.

SAPs was a very big part of older oil formulas and provided a boundary layer in older engines, modern oils lack high SAPs due to EPA regulations, but their loss isn't noticed in modern engines due to tighter tolerances, better oiling systems, and better designed lubrication qualities. But using high end synthetic oils in older engines is potentially damaging without proper additives to restore that missing SAPs as older engines will have momentary points at start-up and higher ranges where the oil isn't splashed on the components enough to provide proper lubrication (hence the boundary layer in older oils.)

You're right in that the mechanical properties of a differential have not changed, but oil have made huge technological leaps and bounds these days. There's a reason many manufacturers are going with synthetic oils in their products.

I'm not knocking your statement as I don't doubt Dana said something like that, I'm more curious as to their research and findings in the face of the modern scientifically backed trend of synthetics being a better choice.
 
It's not just Dana. Big companies like Eaton and Dynatrac that lead the industry in truck axles will actually void warranty on parts if syn is used. New oils are great for engines, terrible for gears.

Most of the synthetic stories are pushed by internet chatter. Take Mobil 1 for example. Everybody thinks it's the holy grail of engine oils based on internet chatter. Truth is, it doesn't meet new vehicle specs as well as cheaper oils. Some of it's properties are the bottom of the barrel. Yet it flies of the shelves. You gotta be careful what you read online.

I'll try to post some data later
 
Thank you for your time and knowledge. The information and how much I'm learning is great. I was a shop mechanic in the 80's and it was straight 90 dino for all gear related components.

Amazing how gear oils have changed. Seems gears haven't changed so much though. I thought tolerances have changed but I would hazard a guess and say it would be incredibly expensive to do so.

I am sure others are as interested as I am. I admit I saw Amsoil 100k (normal conditions) gear oil change interval. Looking forward to learning more. Many thanks.
 
Don't want to beat up the topic. This is my 1st all wheel drive. Manual states transfer case is essentially limited slip differential. Does anyone recommend something specific? Manual doesn't mention friction modifiers just gl-5 75w90. Toyota uses conventional gear oil for mine but I can't buy it from them.

I am not sure if I need the limited slip additives or not (for transfer case). I'm not familiar with it. Seems all the synthetics have LS additives. Okay for AWD x-fer case? Or too "slippery"?

I can't afford to pay for every service. Retired and limited income. I don't know much about these transfer case gear oils. I am ok with differentials now. Just not sure about transfer case. Thanks for time and patience.

Thank you for your help.
 
Thanks for advice and information. I appreciate everyone's help. I'll be doing my own gear oil changes now. Not only keep Runner well maintained, save money too. Thanks again.

Staying conventional and shortening changes to around 20k miles (full time awd), depending on driving conditions.

Found my rear diff vent (top of differential) was clogged. Found out when checked fluid and fill plug shot out from pressure. Soaked and cleaned and reinstalled. Found info in forum on how to extend it. Inexpensive and think great idea.
 
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When I did mine in March after buying this thing, I used the same thing in the axles and transfer case. I think it was 80W90 Walmart brand gear oil, but it seems that I had some Walmart brand 75W90 synthetic BLEND gear oil left over from a project years ago and I might have put that in the transfer case. Can't remember now. In any case, no need for ultra expensive stuff...just change it with the proper viscosity and make sure you use a new crush washer on the plugs whenever you do it to help prevent leaks. The dealer has the washers for only a dollar or two.
 
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