Eaton true track fluid opinions.

Ok this is a broad topic. Eaton recommends a non synthetic fluid for this diff with no ls additive. I am a firm believer in the ford 75w140. Has anyone used this with a eaton and do you think it would be bad for it? Thanks.

Dont go against there rec. I've had customers switch to my duolec just because of crazy locker issues.


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Ok. Thanks. I will take that advice. I called eaton and he said use 80w90 non synthetic for optimum lockup. Ford actually has this so I will go that route .

Im running non-syn 80W90 in the pulling truck with a Detroit in the rear axle. I believe most lockers do not recommend full synthetic.

I've ran 75-140 in 3 or 4 of my trutracs. No problems as of yet. I can not see the reasoning to not run it. JMO.

Same here , the shop I bought it from recommended staying synthetic . Been using it since 2007 .

Most synthetics are not synthetic any longer. Its like calling something billet, ****s gotten to mean nothing. Basically, they don't want you running a group 4 PAO. One of my customers had issues with ARB because of this, so it can cause issues. It might not always, but it is something thats happened.


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I don't mind swapping to the non synthetic and 80w90. But I always wondered if the change affects any other rear end componets

As long as you use a gl5, you should be good. But if its not causing an issue, theres no need to change. But keep a close eye on it. For whatever reason, these 10.5s eat gear oil much faster than other rears. I still cant believe Ford specs the new rear ends as lifetime fluids... No way.


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I have had this in my truck since about 14,000 miles when I swapped in the True Trac - http://www.redlineoil.com/product.aspx?pid=134&pcid=4

Creeping up on 100k, will run the same again.

Ill send you a sample kit, and have it run. You won't run it that far ever again. Granted, not running the Ford stuff for a hundo probably helped...
I like poly esters, they have some fantastic capabilities in high heat applications. They don't shear easily and the dont oxidize quickly. But I doubt their inherent EP ability, and that's probably why Redline doesn't list the FZG, as it's probably just a 12plus like everyone else's.

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Personally I run 75-140full syn which is ford recommended. 80-90 imo is too thin for any continuous driving, particularly towing. The 10.5 runs warm and needs the thicker multi grade. 150f is normal for highway unloaded temp, and can go as high as 230f towing on the highway. The dana 60 can use 80-90 because it will never get that warm. I would put the life of the bearings and the ring/pinion teeth before the functionality of the tru-trac.
Having said that Ive been running a tru-trac in two of my trucks with 75-140 full syn for years now and they both torque up both wheels evenly, very well. The tru-trac still does wonders off road and on the strip for me. The tru-trac is an amazing limited slip/locker no matter what you end up doing.

My point is that full syn means nothing. It's like calling something billet. The Redline is mostly syn, but not a PAO group 4, which is what eaton, arb, ect ect don't want you using. Redline is a poly ester group 5 synthetic. Fords full syn is maybe a group 3, and allowed to be called a synthetic. Hell, im seeing group 2s being called 100% synthetic now. PAOs cost big dollars as a gear oil 25$ and up a quart. You cant get them for less any longer as Exxon Mobil slowed production on them, unless you by in large bulk quantities.
The locker manufacturers want you to not use true PAOs. And it's unlikely you will find one.
Group 3s are great oils, and carry additive packages easier and better than a PAO without all the extra chemistry to do so. Hell, we use a group 3 in our PAO to carry our additive package in a few of our oils. Plus PAOs need expensive esters for seal compatibility. They are spectacular lubricants, but they're being swagger jacked by lower quality oils everywhere now.



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Jim. This is all good info. Eaton told me on the phone I will be just as protected with ford 80w90 even though it's not synthetic. And tge carrier would have better lubrication being the thinner oil. What would you do. 80w90 gl-5 ford non synthetic. Or 75w140 gl-5 ford synthetic.

This is something ive been working on. Footlong has a point about heat, but there are a lot of guys running 80-90 with success. Im about to test a middle of the road straight 120 this weekend. We have had a lot if luck doing that with hub oil in tractor trailers. But I would just run 75-140 to be safe.


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Ok well good to hear from someone who has used it with a true trac as well with no issues. I want to keep using the 75-140 just because it came with that and I have had no issues.

I was just looking up the capacity on my AFE diff cover and noticed they are shipping the covers with a 75-90 fluid... Hmmm interesting.


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Eaton seems to be more concerned with using an oil with little to No limited slip additives (friction modifiers) in it, as these will reduce the bias ratio (the ability to lock) of the unit. I had 2 pails of Chevron 80w/90 Gearlube in the shop so that's what mine are running in.

All gl5 oils should have the modifier in them. And now that everything is called a synthetic I think they are basically not worried any longer. Venom had issues with Amsoil, Royal Purple, as well as our 9919 with detroits and ARBs (mostly ARBs). All real group 4 pao's.

And Chevron... Gross!


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Ok well I've talked to a few more people that back up what eaton says. 80w90. Said it just plain works better for the unit. Will not harm bearings coming from 75w140. I ordered a magtec cover as well for extra capacity.