All,

The front diff is leaking like a sieve, seemingly where the axle tube goes into the diff housing, and I can't see any damage. Any ideas on where to start?

Thanks, Dave.



Aerostard 4wd leaking front diff

 

On that side there is a breather valve near the top, center-ish, I would check that to see if it blew out. There is no seal for the shaft tube going into the dif, but there is a miniscule chance the there is a crack there, and the only thing you can do is JB weld or replace.

 

Ok, thanks.

 

100% full timing running diff with 30% of engine HP driving it.

Breather plug can also plug, causing pressure inside diff, pushes lube out.
Also switch to Mobil 1 75w90 hypoid lube like the rear diff.
The ATF Ford puts in is too thin and has far less antiwear antifriction additive. Causes high temps and thins ATF further causing leaks.
Been running M1 150,000 + miles

 

When I replaced the ATF in the front axle with 75W90 Mobil 1, the stuff overheated and spewed out of the vent tube. I think the gear lube is just too thick for that little axle, creating all the excess heat.

 

Here is a TSB from Ford on this issue, it is obsolete from Ford, but they moved the vent to the top of the cover so it was higher up:

TSB
98-23-3

• AXLE - FRONT - FRONT DRIVE AXLE FLUID LEAK FROM VENT

[************]Publication Date: NOVEMBER 6, 1998[/COLOR]
LIGHT TRUCK:
1990-1997 AEROSTAR
ISSUE:

Front drive axle fluid may leak out of the vent under some driving modes on some vehicles. This may be caused by the design of the vent.

ACTION:

Install a revised front axle cover assembly which incorporates a baffled vent and plug the original vent. The service procedure is detailed in the Instruction Sheet included in the Axle Cover and Baffle Kit.


The Axle Cover and Baffle Kit (F79Z-4033-AA) includes the following:

• One (1) Baffled Cover
• One (1) Vent Hose
• One (1) Plug (for original vent)
• One (1) Instruction Sheet

PART NUMBERPART NAME
F79Z-4033-AAAxle Cover And Baffle Kit

 

I can't tell from what you posted, but is the kit supposed to be installed some place other than the axle tube? Like maybe on top of the axle housing? Is there enough clearance?

 

Fixed it, sometime copy/paste go wacky.

 

It looks like if you want, you can modify you original cover to move the vent upward and plug the current vent. I don't have any pics of the new cover to show.

 

Excellent info: thank you.