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:
A quality petroleum (mineral) based oil is recommended. Synthetic oils and friction modifiers should not be used, as they will decrease overall performance.
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
ďLubricationĒ section of this product manual for further
details and specifications.
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.