RodneyWright wrote:
Dick, I had the clutch pack installed via a friend, so there's no "going back to the mechanic" option there. I actually helped w/ the work, so I didn't see anything weird when we put it back together. It was not the new tires as that was a consistent noise and a low "roar". What I heard was a drill in your skull noise...
When I swapped the ZII's back for the street tires, I noticed gear oil on the inside of the rim of the left rear wheel, that in itself is not a good sign and I'm probably in need of outer axle seals at this time. I think I'm going to be brave and pull the center gear set, remove the axles and replace the seals and add new gear oil. I'll check for metal by dropping the diff cover. If I see metal, I'll put it back together and seek professional help. If no metal, I'll replace the seals and add new gear oil and go from there.
Drill in your skull noise sounds like time for professional help of some sort . . .
FYI my impression is that if the axle seals are leaking it frequently means the bearings and integral race on the axle are worn. Which I think means either a new half shaft or an "axle saver bearing". Of course it could also be seal damage during the clutch plate project since it apparently is pretty easy to do so.
Diff oil low enough to make nasty noises would seem to have made a pretty big mess.
For reference here is a copy of the complete Ford rear axle NVH diagnostic info from the 2012 manual.
Quote:
Condition Possible Sources Action
Axle howling or whine
Axle lubricant low
CHECK the lubricant level. FILL the axle to specification. REFER to Section 205-02 .
Tuned dampers missing or incorrectly installed
REFER to the TSB and follow the procedure outlined.
Axle housing damage
INSPECT the axle housing for damage. REPAIR or INSTALL a new axle as necessary. REFER to Section 205-02 .
Damaged or worn wheel hub bearings
CHECK for abnormal rear wheel bearing play or roughness. INSTALL a new wheel bearing as necessary. REFER to Section 205-02 .
Damaged or worn differential ring and pinion
INSPECT and INSTALL a new differential ring and pinion as necessary. REFER to Section 205-02 .
Damaged or worn differential side or pinion bearings
INSPECT and INSTALL new differential side or pinion bearings as necessary. REFER to Section 205-02 .
Driveline clunk — loud clunk when shifting from REVERSE to DRIVE
Incorrect axle lubricant level
CHECK the lubricant level. FILL the axle to specification. REFER to Section 205-02 .
Excessive backlash in the axle
CHECK the ring gear backlash. REPAIR as necessary. REFER to Section 205-02 .
Damaged or worn pinion bearings
REPAIR or INSTALL new pinion bearings as necessary. REFER to Section 205-02 .
Damaged or worn U-joints
INSPECT the U-joints for wear or damage. INSTALL new U-joints or driveshaft as necessary. REFER to Section 205-01 .
Driveline clunk — occurs as the vehicle starts to move forward following a stop
Worn driveshaft CV joint or U-joints
INSPECT the CV joint and U-joints for wear. INSTALL a new driveshaft or U-joints as necessary. REFER to Section 205-01 .
Loose axle mount
CHECK the axle for loose bolts. TIGHTEN to specification. REFER to Section 205-02 .
High pitched chattering — noise from the axle when the vehicle is turning
Incorrect or contaminated lubricant
CHECK the vehicle by driving in tight circles (5 clockwise, 5 counterclockwise). FLUSH and REFILL with the specified rear axle lubricant and friction modifier as necessary.
Damaged or worn differential (differential side gears and pinion gears)
REPAIR or INSTALL new differential side gears or pinion gears as necessary. REFER to Section 205-02 .
Rumble or boom — noise occurs at coast/deceleration, usually driveshaft speed-related and noticeable over a wide range of speeds
Excessive driveshaft runout and/or driveshaft is out-of-balance
CHECK the driveshaft runout and balance. REFER to Driveshaft Runout and Balancing in this section.
Binding or seized U-joints
ROTATE the driveshaft and CHECK for binding or seized U-joints. INSTALL new U-joints or driveshaft as necessary. REFER to Section 205-01 .
Grunting — normally associated with a shudder experienced during acceleration from a complete stop
Binding driveshaft CV joint
INSPECT the driveshaft CV joint for binding. INSTALL a new driveshaft as necessary. REFER to Section 205-01 .
Loose axle mount bolts or suspension fasteners
INSPECT the rear suspension and axle. TIGHTEN the fasteners to specification. REFER to Section 205-02 .
Howl — can occur at various speeds and driving conditions. Affected by acceleration and deceleration
Incorrect ring and pinion contact, incorrect bearing preload or gear damage
INSPECT and REPAIR as necessary. REFER to Section 205-02 .
Chuckle — heard at coast/deceleration. Also described as a knock
Incorrect ring and pinion contact or damaged teeth on the coast side of the ring and pinion
INSPECT and REPAIR as necessary. REFER to Section 205-02 .
Knock — noise occurs at various speeds. Not affected by acceleration or deceleration
Gear tooth damage to the drive side of the ring and pinion
INSTALL a new ring and pinion. REFER to Section 205-02 .
Scraping noise — a continuous low pitched noise starting at low speeds
Worn or damaged pinion bearings
INSPECT and REPAIR or INSTALL new pinion bearings. REFER to Section 205-02 .
Driveline shudder — occurs during acceleration from a slow speed or stop
Incorrect transmission crossmember orientation
CHECK for correct orientation. REINSTALL if necessary. REFER to Section 502-00 .
Center bearing spacer missing or incorrectly installed
CHECK for correct installation of center bearing spacer. REFER to Section 205-01 .
Drive axle assembly mispositioned
CHECK the axle mounts and the rear suspension for damage or wear. REPAIR as necessary. REFER to Section 205-02 .
Loose axle bolts
CHECK the axle for loose bolts. TIGHTEN the bolts to specification. REFER to Section 205-02 .
Driveline angles out of specification
CHECK for correct driveline angles. REFER to Driveline Angle Measurement in this section.
U-joints binding or seized
ROTATE the driveshaft and CHECK for binding or seized U-joints. INSTALL new U-joints or driveshaft as necessary. REFER to Section 205-01 .
Binding or damaged driveshaft CV joint
INSPECT the driveshaft CV joint for binding or damage. INSTALL a new driveshaft as necessary. REPAIR as necessary. REFER to Section 205-01 .
Driveline vibration — occurs at cruising speeds
Missing weights or damage to driveshaft
INSPECT the driveshaft. INSTALL a new driveshaft as necessary. REFER to Section 205-01 .
Worn U-joints
CHECK for wear or incorrect seating. INSTALL new U-joints or driveshaft as necessary. REFER to Section 205-01 .
Misalignment of yellow dot on driveshaft-to-yellow dot on pinion flange plus or minus 1 bolt hole
REINSTALL driveshaft with yellow dots aligned plus or minus 1 bolt hole. REFER to Section 205-01 .
Worn or damaged driveshaft center bearing support
CHECK the insulator for damage or wear. ROTATE the driveshaft and CHECK for rough operation. INSTALL a new driveshaft as necessary. REFER to Section 205-01 .
Loose axle pinion flange bolts
INSPECT the axle pinion flange. TIGHTEN the pinion flange bolts to specification. REFER to Section 205-01 .
Excessive axle pinion flange runout
CHECK the pinion flange runout. REPAIR as necessary. REFER to Pinion Flange Runout Check in this section.
Excessive transmission flange runout
CHECK the transmission flange runout. REPAIR as necessary. REFER to Specifications in this section.
Binding or damaged driveshaft CV joint
INSPECT the driveshaft CV joint for binding or damage. INSTALL a new driveshaft as necessary. REFER to Section 205-01 .
Excessive driveshaft runout and/or driveshaft out-of-balance
CHECK the driveshaft runout and balance. REFER to Driveshaft Runout and Balancing in this section.
Driveline angles out of specification
CHECK for correct driveline angles. REPAIR as necessary. REFER to Driveline Angle Measurement in this section.
Transmission mount not centered
NEUTRALIZE the transmission mount. REFER to the Transmission Crossmember procedure in Section 502-00 .
Analysis of Leakage
Clean the leaking area enough to identify the exact source.
A plugged axle housing vent can cause excessive pinion seal lip wear due to internal pressure buildup.
Verify the lubricant level is at specification.
Axle Vent
A plugged axle vent causes excessive seal lip wear due to internal pressure buildup. If a leak occurs, check the axle vent. If the axle vent cannot be cleared, install a new axle vent.
Drive Pinion Seal
Leaks at the drive pinion seal originate from the following causes:
Damaged seal
Worn seal journal surface
Any damage to the seal bore (dings, dents, gouges or other imperfections) distorts the seal casing and allows leakage past the outer edge of the drive pinion seal.
The drive pinion seal can be torn, cut or gouged if it is not installed correctly. The spring that holds the drive pinion seal against the pinion flange may be knocked out and allow fluid to pass the lip.
Metal chips trapped at the sealing lip can cause oil leaks. These can cause a wear groove on the drive pinion flange and result in drive pinion seal wear.
When a drive pinion seal leak occurs, install a new drive pinion seal and check the axle vent to make sure it is clean and free of foreign material.
Install a new drive pinion flange if any of these conditions exist.
Drive Pinion Nut
NOTICE: Install the drive pinion nut to the correct torque specifications or damage to the differential components may occur.
On some high-mileage vehicles, oil may leak through the threads of the drive pinion nut. This condition can be corrected by installing a new drive pinion nut and applying threadlock on the threads and nut face.
Differential Seals
NOTICE: When installing shafts, do not allow splines to contact seals during installation or damage to the seals may occur.
Differential housing seals are susceptible to the same types of damage as drive pinion seals if incorrectly installed. The seal bore must be clean and the lip handled carefully to avoid cutting or tearing it. The seal journal surface must be free of nicks, gouges and rough surface texture.
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) it seems like a waste unless a supplier can get you extremely close with a recommended setup. 
