Eaton Gear Oil Recommendations for the Truetrac

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The G80 auto locker stopped locking in my 06 Sierra, so I just had an Eaton Truetrac installed. My initial impressions are very good (but very limited at this moment). It seems very smooth and both wheels hook up when needed.

I read through this earlier thread regarding fluid recommendations. Though the thread is somewhat old, the recommendations are still valid for the most part.

Here's what Eaton says today in the documents currently on their website:

Detroit Truetrac
A quality petroleum (mineral) based oil is recommended. Synthetic oils and friction modifiers should not be used, as they will decrease overall performance.

Detroit Truetrac®
What kind of oil should I use? Can I use synthetic?
Do I need friction additive/modifier?
Truetrac units perform best when using GL5 mineral /
petroleum based gear oil. Synthetic lubes are
discouraged. Do NOT use friction modifier additives or
lubes formulated with friction modifiers. See the
“Lubrication” section of this product manual for further
details and specifications.

Lubrication Specifications
Detroit Truetrac®
High quality mineral or synthetic gear lubes are
required for use in Detroit Truetrac differentials.
Regardless of the lube type, always use a GL5 rated
lube with the least amount of friction modifier. Mineral
lubes lacking friction modifiers (limited-slip additives)
were historically recommended for all Truetrac
applications because friction modifiers can slightly
reduce the bias ratio (limited-slip aggressiveness) of
Truetrac differentials. However, to address the
continually increasing power outputs of modern
powertrains, many vehicle manufacturers have
switched to synthetic lubricants as a counter measure
for increased axle temperatures and prolonged service
intervals. In general, consult the vehicle owner's
manual for the manufacturer's recommendations for
lubrication type, weight and fill volume. This will ensure
lube compatibility with the seal materials and bearings
used in the axle. Eaton Performance technical support
is available for any concerns in lube selection.

I was told that mine was filled with Mobil 1 when they did the install. I'm planning an oil change in a month or so, and I plan to install a conventional mineral oil without limited slip additive at that time. Unfortunately it appears most of the "majors" now include LS additives in all of their gear oils now. It appears that many of the "store brand" gear oils still lack the LS additive, so I'll probably choose one from among them.
 
It's probably saying syn is not recommended because most of them come with an LS additive that can affect the performance of the truetrac. There are a couple of syn gear oils without the LS additive such as Redline 75W90NS or Eneos 75W90.
 
Looks like Redline has dropped their 75W90NS. Apparently their NS oil is now limited to one 75W140NS offering.
 
While I cannot speak from experience for the Truetrac differential, the Detroit Locker carries the exact same lubricant recommendation from Eaton. I'm using Chevron Delo 80w-90 ESI gear oil (which is a GL-5 conventional lubricant) with my Detroit Locker and it's smooth as can be.

I did a significant amount of digging about on internet forums trying to figure out Eaton's peculiar oil recommendation, and the general consensus is synthetic oils cause the differential operation to be much rougher/louder than with conventional.

The simple fact that your installer is using Mobil 1 is a good indication that it probably does not matter at all whether you use synthetic or conventional. If you want my honest opinion, problem free operation of these things has everything to do with a proper install; as long as you are using a gear oil at the viscosity recommended by GM, and without included friction modifier you're in good shape.
 
I have one of those in my F-450 in my sig, just use any ordinary gear oil in the correct weight, it'll be fine. The shop that installed mine actually added LSD additive to it (even though I told them NOT to), but it still seems to work OK.
 
Needs friction to work. Best to use a nonlsd gear oil.

Redline NS, Motul...and over the road truck gear oils are great choices. What weight do you require?
 
Originally Posted By: Brian Barnhart
Looks like Redline has dropped their 75W90NS. Apparently their NS oil is now limited to one 75W140NS offering.


Is this true? It is still on their website:

http://www.redlineoil.com/product.aspx?product=58304

I am asking because in my LS applications I prefer to buy the NS product and dial in the amount of additive required rather than using a premixed LS fluid. As well, several locking differential styles do not require LS additives so I hope the non-LS fluid market does not vanish.
 
Motul makes both a great full synthetic AND a mineral based gear oil without the friction modifiers.

Torco makes a great mineral based gear oil (RGO), I believe also without the additive.
wink.gif
 
Originally Posted By: marc1
Originally Posted By: Brian Barnhart
Looks like Redline has dropped their 75W90NS. Apparently their NS oil is now limited to one 75W140NS offering.


Is this true? It is still on their website:

http://www.redlineoil.com/product.aspx?product=58304

I am asking because in my LS applications I prefer to buy the NS product and dial in the amount of additive required rather than using a premixed LS fluid. As well, several locking differential styles do not require LS additives so I hope the non-LS fluid market does not vanish.


Oops, my mistake. I looked for it under the Gear Oils for Differentials. It's listed among the Gear Oils for Manual Transmissions even though it is also suitable for differentials. I will definitely consider it for my Truetrac.
 
The TrueTrak is a helical gear LSD device. It does not have clutches; it relies on the CoF (co-efficient of friction) between the gears and the housing to initiate it's effect of bias drive. These units are delivered with a set bias from OEM and it cannot be changed. The clearances are very specific to these type units. If you use the wrong fluid, it will alter the CoF and the bias will not respond correctly. You should NOT use syn or a friction modifier additive, or a lube with FM already in it.

The Detroit Locker (same as a No-Spin) uses a spring loaded locking dog tooth system; it's not the same as the helical gear TrueTrac, but it does have the same fluid requirement.


For the TrueTrac use ONLY a GL-5 fluid that is NOT syn or FM modified. Be careful, because some dino gear oils still have FM in them. I would recommend a simple choice such as the W/M SuperTech GL-5 80w-90. Easy to get; meets the criteria.

These units are very reliable and have great longevity. They don't need anything special to survive; just the right fluid.


Sideline Q:
What happened to the G-80? Grenade itself? Not unheard of. That "M-Locker" is great in theory, but fails at times when put to hard use. The TrueTrac is a common "upgrade" for these units. Which axle do you have? AAM 11.5 in a HD, or a 1/2 ton?
 
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The G80 didn’t grenade, but wouldn’t drive both sides any longer. I didn’t find any broken parts in my somewhat cursory inspection, so I suspect the small clutches were gone. As far as I can tell, it stopped locking after a few donuts in the snow. It had regular fluid changes and 108,000 miles on it. It’s a 8.6” in a ½ ton.

I’m very happy with this unit. It’s much nicer than the M-Lock. I’m fairly certain the installer filled it with M1 75W90, which is (obviously) synthetic, and has FM added. So I’m going to change it out soon.

My preference would be a non-synthetic 75W90 with no FM. I don’t really want to give up cold flow and increase drag by using an 80W90 or 85W140 conventional. Including FMs in gear oils has become commonplace and it’s getting hard to find anything other than house brand 80W90 without it. Some of the 75W90 gear oils marketed for OTR appear to lack FMs, but like their "automotive" counterparts, most are synthetic.
 
Originally Posted By: dnewton3
I would recommend a simple choice such as the W/M SuperTech GL-5 80w-90. Easy to get; meets the criteria.


Is this product void of LS additives? If so that is great. I used to use Castrol Hypoy C but I cannot find it anymore, I can only find the new bottles that infer there is an LS component in it.
 
Yes - I believe the dino ST 80w-90 gear oil is devoid of any FM. I suspect that's true of the semi-syn gear oil as well, as they both mention "for top off of LSD" or something akin to that. The implication being that they have no FM, so they are not a replacement fill for LSD applications. (of course, you can use it and then add FM additive if needed; it's presumably not in the GL-5 bottled ST product).

I think the only product they offer with FM in it is their full-syn 140 grade; it does mention LSD application.

As always, check directly with them for yourself; don't take my word for it.
 
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In my search for a good 75W90 Truetrac fluid I’ve found –

Conventional:
Coastal (Auto Zone house brand, conventional)

Synthetic:
Master Pro (O’Reilly house brand)
Chevron Delo
Mobil Delvac
Redline NS
Motul Motylgear (“Technosynthese” - semi synthetic? or possibly Group III?)
Torco SGO.

At this point, I’ll most likely try the Coastal first since it’s conventional, available locally, and low cost.

Seems all the other readily available conventionals are 80W90 and/or contain LS additives. The other readily available synthetics appear to contain LS additives as well.

The Amsoil offerings don’t say whether they contain LS additives or not. They say their fluids are compatible with most LS differentials, but also say to add a LS additive if chatter occurs. Not sure how to interpret that. Sounds to me like it is slippery enough, or that there is enough FM in the oil, for most LS applications. But extra slippery and FMs are something I want to avoid.

In all fairness, I’m not really unhappy with the M1 (Synthetic and LS additives) that I was told is in there now. Of course, I’ve only been using the Truetrac a week. At any rate, I would rather use something closer to what Eaton suggests.
 
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I was just in NAPA, and they had a mineral based (white bottle) Valvoline 75W-90 right on the shelf.

I was not paying attention as to whether or not it had the friction modifier in it or not, but if it does not, that could be another fairly easy to get choice.
wink.gif


The Lakewood BFL (yellow label) is good stuff as well, but it definitely has the FM in it, so it's a no go for you.
frown.gif


Yes, most I know with a Truetrac say they are STRONG, quiet, and seamless/invisible in operation.
My only complaint with them (besides COA), is their lower bias than some other units out there (including some other Tosen/worm gear types), if one needs that.
 
Originally Posted By: dailydriver
I was just in NAPA, and they had a mineral based (white bottle) Valvoline 75W-90 right on the shelf.

I was not paying attention as to whether or not it had the friction modifier in it or not, but if it does not, that could be another fairly easy to get choice.
wink.gif


The Lakewood BFL (yellow label) is good stuff as well, but it definitely has the FM in it, so it's a no go for you.
frown.gif


Yes, most I know with a Truetrac say they are STRONG, quiet, and seamless/invisible in operation.
My only complaint with them (besides COA), is their lower bias than some other units out there (including some other Tosen/worm gear types), if one needs that.



Caution here; the white bottle has FM in it.
Check closely before using, as FM in the Truetrac is a BAD idea.
http://www.valvoline.com/pdf/high_performance_gear.pdf
 
you guys are going crazy with the friction modified limited slip gear oils.
i get the impression you all think the friction modifier and "syntheticness" of the oil reduces friction so much that it causes the differential not to lock up. it will work and lock up just fine, the force of the gears that lock up against the differential case causing the positraction is substantial, no oil is going to reduce friction so much as to prevent lockup. any difference in performance among all the oils is negligible, and whatever you use in no way will hurt the differential. the only way you can hurt it is to run it low on oil, or add so much friction modifier additive to the oil that it breaks down the oil causing lubrication failure, which will happen first at the ring & pinion interface. what drives the lubrication requirement in an axle is the hypoid gear interface of the ring and pinion, which needs a gear oil having EP additives thus GL-5. the differential is along for the ride and has no real oil requirement, this i was told by torsen tech when i asked years ago about using the friction modifier additive which my GM owners manual to the camaro said to use without mentioning anything about the 3 different types of diffs that came in those cars. All the friction modifier does is allow differentials with clutch packs to slip smoothly, when in a turn spring pressure reduces load on the clutch pack and they are expected to slip the slipping is smooth and not a slip-grab-slip-grab chatter. it's not the friction modifier that allows the slip to happen, it's the reduction in spring pressure against the clutch pack.
 
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