justintyhme

Just had a 2nd brand new axle go out. Total catastrophic bearing/axle failure. (complete with flames out of the wheel well)

Story: replaced gears from 3.73 to 4.56 with truetrac in shop. Shop suggested new axles. I purchased L and R axles online and brought to them. Left axle burned up at about 44 miles. Replaced with new again same manufacturer. Right axle blew out at 450 miles while trailer towing.
1999 S923A 9.75 Axle (uses 8.8 wheel bearings thus the "franken axle") No problems prior to gear change.

NOW...I pulled the previously replaced left axle again and observed the attatched wear pattern.... Is this the cause of my woes? Note the unusual wear pattern on the axle. It is just the edges of the bearing making contact. Don't know if this is normal or not for a break in period......anyone?

Jefk

you said you replaced the axles if i read correctly.so maybe put the stock ones back in and see how that works. either that or your new found torque is turning the diff fluid into napalm and blowing the axles(power of ford baby XD). now that i mentioned that.. is it possible the axles you bought are underrated for what your doing?

justintyhme

Well...the first one blew out at 44 miles and no load at all. No speed above 65. I was doing the break-in period on the new gears. The original axles were showing some metal fatigue due to normal long term use. So I still have them but I will not put them back in because I wanted something that would last the life of the truck.

More importantly....what about the wear pattern? What do you think?

jferg92

On the new axle wear, can you catch your finger nail on the marks?

justintyhme

I do not believe so but will check that test out more tonight.

Carcrazygts2

Get better bearings and a set of either Dana or O.E. Motorcraft axle shafts. I have had the same issue. Only way to fix it is Motorcraft bearings and Better axle shafts. Also run the diff about .75qt over full. I fill mine to the fill plug. Then pull the ABS speed sensor in the top of the diff and add about .75qts to it.

Jefk

x2

w0lvez

Based on the Picture it's either the bearing was not properly seated or you installed it dry without any prelube. Measure how deep the bearing sits using a caliper and compare it to the wear.

GEARS always need 500-1k miles of break in period on mineral based gear oil. It also need to be adjusted. Gear oil must be change after 500 miles.

There is also a Maximum Tire diameter depending on the gear.

I suggest to Use the factory gears, put a smaller wheel (16 inch) and have the PCM calibrated for the wheel.

Check if the differential housing where the bearing sits for any damage.

Use a Bearing/Seal Tool when installing the bearing. The sound will change when the bearing is already seated. If the differential is not a limited slip make sure the VENT HOSE/TUBE is not clogged and use grease, assembly lube or gear oil as prelube on both the bearing and axle.

Seals should be coated with lithium grease.
Never use Grease on Pinion & Carrier Bearing

Check this pdf

justintyhme

Thanks for your continued help folks. The manufacturer owned up to "bad bearings" and has reimbursed all my expenses including the labor. WOW!

To answer previous questions, the axles were installed by a pro shop. So, I do not know if they were pre lubed. All other break-in rules were followed to a "T".

Carcrazygts2

Glad they owned up to it. I stick with Motorcraft bearings for the franken axle. Its pricey but the only way to make them live.