Specifications

good “feel” for what it should be, then do your best to apply that same “feel” to the fill plug
using your regular socket wrench.
Time to refill the axle:
IMPORTANT: Read the latest GM TSB regarding rear axle chatter to determine which GM gear
oil / additive and amounts you should be using. This info has changed over the years and is
subject to further periodic change. The latest axle TSB (as well as previous axle TSBs) can be
found in post #2 of this thread:
http://forums.corvetteforum.com/show...24&postcount=2
As of January 2008, the oil specified for use in the Corvette differential is Dextron LS Gear Oil
75W-90, part #88862624 (#88862625 in Canada). No additive is required or recommended –
just add straight Dextron LS 75W-90 only.
Your C6 differential requires roughly 2 quarts (check manual and/or TSB for exact specs for
your year / model). But be sure to have at least 3 quarts of oil handy since it is almost
impossible to squeeze all the oil out of the bottles into the axle, plus you’ll likely spill some
anyway.
Since you will not be able to get the oil bottles higher than the fill hole, you must pump or
squeeze the oil up into the hole.
The GM oil bottles come with extra pointed nozzle caps and a short piece of clear tubing. I
found this set up to be too short and too small a diameter, plus after a while the nozzle gets
oily and the hose starts slipping off the nozzle no matter what you do. One solution is to buy an
aftermarket fill tube at the local auto store. The product I found (at Pep Boys) is made by
Hopkins Manufacturing, called a “FloTool”… it threads right onto the GM oil bottles and has a
12” long section of clear tubing attached… twice as long and larger diameter than what you get
with the GM oil bottle. This FloTool fit really nice and made the oil fill a breeze.
Insert the tubing into the fill hole of the axle holding the gear oil bottle up between the mufflers
and squeeze the bottle. You will see the oil flow through the tube and into the axle. One
headache though is that you can only get about half or two thirds the contents of the bottle into
the axle even if you squeeze / crush the bottle as hard as you can… so you need to refill the
bottle and repeat. This is the main reason to have at least one extra bottle of gear oil on hand.