2008 ST Central Junction Box Fuse 2 & Rear Differential Questions

[vmi95]

Been a reader for a while and I appreciate all the help on this forum.

I've got 2 problems, however, that I cannot find the answer to:

I have a 2008 Sport Trac that is starting to develop problems. First, for a while, my battery has had terrible life. My wife blamed the GPS or radar detector, but even with them unplugged, my battery dies quickly, sometimes only a few days after a full charge. The dealership replaced the battery. The positive post of the battery gets VERY corroded, very quickly. Since I treated it, it has slowed the corrosion. I have OEM battery and cables.

Today, I did a parasitic load test. I hooked the meter between the negative post of the battery and the cable. After everything went to sleep, it was measuring about 165 mA. I started in the battery junction box and pulled all of the fuses. I pulled all of the fuses in the central box working backwards. Of course, it was the second to last fuse -- fuse 2, 5 amp -- that caused the load to drop down to a few mA.

What does the central junction box fuse 2 control? Does anybody have any idea where I should start troubleshooting?

Second, I've been having strange power lags in the 30-50 mph range with a whoop-whoop sound (sorry to be so technical) coming from the read-end. My dealership didn't reproduce the problem, which happens every time I drive the car. STS told me that I need a new rear differential.

What are the symptoms of a bad rear differential? Does that make sense? Also, STS suggested a rebuilt unit. Can anybody give a ballpark range for a reasonable rebuilt unit and installation and whether a rebuilt is recommended?

I finally own the ST, which I bought new and love, and need it to last several more years. Having to jump the it in the supermarket lot and worrying about the rear end locking up is getting to me, though.

Thanks for the help.

Adam

 

[eppd00]

Are you still within the 5yr/60000 mile drive train warranty?

 

[eppd00]

Also, generally speaking, most folks will change out the bearings and gears rather than getting a rplacement rear end. The 8.8 gears have been around since the late 70's. The IRS is unique to these trucks and a few other Ford vehicles. Again, if you are still within the drivetrain warranty, your rear end should be covered.
Merry Christmas

 

[vmi95]

eppd00,

I am far out of warranty. I am not sure the whole rear end needs replacement or just the rear differential. The mechanic at STS tells me that it is the rear differential.

Thanks.