differential fluid change frequency

April 27, 2008, 02:00:48 PM

84 cougar, 3.8L

Any thoughts on the what the frequency (mileage) should be for changing the differential fluid?

differential fluid change frequency

Reply #1 – April 28, 2008, 01:19:48 AM

do you want actual lubrication requirements from the owners manual?

If your like me,, im sure my 20th needs it.

My 87 white coug has been done twice in my ownership.

IMHO,, if you never did it,, then change the fluid.
from this point forward if there are no leaks,, its probably the last time you will ever have to be in there. Gear box oil of a good sicky thick nature will last the life of a gear system. the thicker the better imho but then again, thats just my opinon.

while you are in there though,, there are a couple things you NEED to look at. There will be two small spider gears in there which spin on a shaft / pin.

you can remove those easy enough and inspect. Your looking for "egged" out spider gears,,meaning>

The hole in the spider gear is no longer actually round or the pin the spider gear rotates on shows a lot of play.
if you find a lot of play,, welcome to the world of the 7.5 and get a new spider gear set and pin. Measure the diameter of the pin in the center and compare it to the diameter on the ends. excessive wear will give you clunk noises which indicates a "lil" too much play but many live with it.

differential fluid change frequency

Reply #2 – April 28, 2008, 03:48:51 PM

Thanks for response jcassity.

David