75w90 conventional vs syn???

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Toyota's call for 75w85 gl5 front and rear which is not common. 75w90 is though. I understand that interchanging those is fine but my question is in regards to paying extra for 75w90 syn over conventional. Is there any advantage? Does syn gear dope actually last longer and or protect better? I had strong opinions in the past but some Tacoma enthusiasts are trying to convince me otherwise Also T case calls for 75w...can I just run the gear dope?
 
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Originally Posted by dave1251
Originally Posted by Doublehaul
Anyone think I'd be better with 75w140?
Only if you tow over 50% of the time.
Yep, don't go there unless really heating it often. Otherwise you just chew up the VIIs, need to change the oil more often and creat more potential problems. 75w90 Syn is worth it IMO, I've run it (vs dino) enough miles/years in Land Cruisers and my Acura SLX (Trooper) to see more longevity. I run 80w/90 as my climate is mild. Do you have an LSD? Because while that doesn't change viscosity choice, it changes additive requirements and potential base unit brand/type selection. Plus this stuff is awesome (Lubegard gear oil supplement): https://www.amazon.com/gp/product/B004BSMI8E/ref=ox_sc_saved_title_3?smid=A3B850ZGIPDG3A&psc=1 Only takes 1oz/qt to make a difference, put it in diffs, MTs, etc. Works.
 
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The following is what I did recently on my brothers 2010 Tacoma calling for 75w85. I plan to run the 80w90 in the front diff until the next oil change and dump it for some 75w90 if it looks ok. I'm going to be doing the front and rear diffs on my moms 2016 4Runner soon with Starfire 75w90(made by Warren Distribution, I suspect it's the same as Walmart Supertech and Mag1 75w90). For the transfer case, I may try the Ravenol equivalent to the Toyota fluid. Ravenol MTF-3 https://www.bobistheoilguy.com/foru...ota-transfer-gear-oil-lf-75w#Post5118386
Originally Posted by BlakeB
2010 Tacoma DCSB (1gr-fe), 42,909 miles Rear Differential: Out: factory fill 75w85 In: Starfire full synthetic 75w90 Front Differential: Out: Factory Fill 75w85 In: Starfire 80w90 The factory fill in the front diff was in really bad shape so I refilled it with some cheap 80w90, I will change it out again with synthetic 75w90 at the next oil change. Transfer Case: Out: Factory fill 75w90 In: Amsoil 75w90 (GL-4) The rear differential and transfer case fluids were in great shape (looked almost new with a minimal amount of fuzz on the rear diff magnet, it did have an odd sliver of metal stuck to it but being the factory fill with close to 10 years of use on it I'm not too worried about it.
 

Astro14

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Originally Posted by Doublehaul
Anyone think I'd be better with 75w140?
I went from M1 75w-90 in the 4Runner to ST syn 75w-140. Made the 4Runner's axle slightly quieter and the 2 Ford's significantly quieter with no loss in MPG. If you do go to 75w-140 use nothing but synthetic and it does no harm.
 
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Only synthetic gear oil. Put regular and synthetic gear oil outside in freezing temps then the next day, pour in to a cup. See which pours easier. Better gas mileage, better lubrication in cold temps.
 
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dave1251 above said, "Changing gear oil should be once in a vehicle lifetime thing unless it becomes containmenated." I bought a low mileage 2005 Ford Ranger FX4 Off-Road recently as many here know. 15 years of service is why I'm changing mine. The OO had 6 boys so who knows. If the FF is newish looking etc., the joke will be on me. It's getting synthetic because almost everyone here says it's slightly better. Many have said there'll be no difference. I wont know either way, will I? Any comments on my 15 year yardstick are welcome. No highjacking of thread intended.
 
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Many FJ owners and this 4R owner are running Mobil Delvac 75W-90 with no issues in T-case and diffs. No LSD friction modifiers. Pretty good price at Summit Racing if you've got one near you.
 
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i put 75-90 redline real syn in my dana-nissan rear diff. nissan uses their costly buy cheap 75-140 semi syn, but a search on the dana site recommended real synthetic 75-90, if i hauled or towed a lot 75-110 lube
 
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Originally Posted by 1000MPH
Many FJ owners and this 4R owner are running Mobil Delvac 75W-90 with no issues in T-case and diffs. No LSD friction modifiers. Pretty good price at Summit Racing if you've got one near you.
What year 4Runner? Same t case as the taco I think
 
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The T case spec changed to straight 75w in 2010 for both the FJ and 4R and in 2016 for the Tacoma. The differential spec for 75w-85 was a little earlier depending on model and trim.
 
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dnewton3

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I'm typically a big advocate for dinos unless conditions warrant. In this case, it qualifies; use the syn! Diff fluid is not under pumping pressures; it's slung. Also needs to flow down the axle tube. Cold temps mean syns are a good idea for this application.
 
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It depends on the use. If we're talking a daily driver, I prefer the thermal stability and aeration control of synthetics. The same for road racing, oval track, or any other endurance application. For something like drag racing, I prefer the higher pressure-viscosity coefficient of conventional (group I and II) oils to better withstand the high shock loads they experience coming off the line. Although that could be made up for with extreme pressure adds and a higher viscosity synthetic.
 
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