Project, long term diff oil test.

[ZR]

2005-->>> GT

As many of the '05 up guys have experienced, x tra prone to leaking axle and or pinion seals.

Factory fill = 75w140 synthetic.
Ride being used to test, diff oil was changed n case cleaned spotless in the early spring, filled with premium 75w40 full syn. Three track days + daily driver miles before cover pulled today, oil looks as brutal as the factory oil did that over 100k on it. Cover is off as it's spewing oil out both axle seals.

The test

Filling with tried n true dino 80w90 + additive. Diff is also getting the proto-type ZR diff vent mod (sounds fanzy don't it, just a length of hose + old skool no pressure type vent)+ a pair of new OEM Ford seals.
We'll change it again early next season and see how well the oils stood up and if it's cured the leaks.

Stay tuned.

PS, test is in no way shape or form intended to promote one brand over another or to put any brand down, simply seeing if perhaps kickin it old school with solve some issues that were not common in the past. After all, diff in the newer rides is basically the same 8.8 diff Fords used since the beginning of time.

[Intmdtr]

Hey Rick, I switch back to the 80w90 when I had the 4.10's installed in 09. Car never leaked after that, just this year it developed a pinion seal leak....so I think the 80w90 did me some good, and it was recommended by an old school rear end guy for Ford.

[Slope]

Subscribing.

[Uncle Buck]

Young or old, no one likes a leaky rear end

[NickD]

Ill prob be seeing you in a month or so (unless I wait till next year) to do 4.10's and the new fancy patient pending ZR diff vent mod,

[ZR]

Considering I flat out love synthetics, will kill me if dino comes out the winner.

[steam_mill]

Interesting...

In the spring, I had my rear end rebuilt with new gears (3.55 - '85 mustang with an 8.8).

So I asked the garage (Star Automatic Transmissions and Differentials) when I should change the oil.

His response was to just leave it alone. Don't ever bother changing it. It will outlive the car!

Considering I drive it 3K/year, probably true.

[Amsoil Guy]

Will you be trying 80W-90 synthetic afterwards as well?

[ZR]

Yes Sir.

[Amsoil Guy]

Excellent!