Can't speak specifically about TC's but, the 8.8 rear is
pretty much the same whether it be in a TC, CV, GM ot F/E
series truck. They are pretty much bullett proof requiring
little maintenance. They do have a propensity to leak at
the pinion or axle seals around 100K or so. I have
routinely replaced the gear oil with a semi synthetic
although, I have never had a problem with regular gear oil
in street cars. Unless you are towing or some other heavy
duty application, I do not see any quantifiable financial
benefit to using full synthetic other than a very slight
gain in fuel economy. Most differentials will far outlast
the vehicle unless they are run low on whatever oil is in
there as long as it is not allowed to run low on oil because
of leaky seals. If you choose to use synthetic oil, I will
defer to the eminently more opinionated oil gurus of the
group to gently direct you to the correct brand to
correspond with the moon phase in which you plan to do the
I remember reading in my Ranger's owner's manual an advisory about
changing the rear axle lubricant. It basically said to *never* change
the gear lube unless the axle had been submerged, because the original
lube was of such a high quality that it was likely to be better than
anything you could buy on the aftermarket, even after 100k miles.
A friend who worked for John Deere some years ago reported a similar
situation, John Deere had to issue an advisory so that customers wouldn't
change out the extremely expensive lubricant in one of their pieces
of heavy equipment. Some farmers had acquired the laudable habit of
being proactive on changing fluids, but they were unaware of the very
high quality stuff that JD put in there (and it was needed due to the
design of the gears involved), and were wearing out gears that would
have lasted 25 years of very hard use on the original stuff, in just a
couple years using garden-variety gear lube.
My take on it would be to go direct to Ford and buy whatever they sell,
synthetic or not.
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.