Front differential rebuild, spider gears are binding

[PlorkZ47]

I just rebuilt the front differential in my 2017 Expedition because one of the bearings was going out (apparently a common problem with these where the bearings and bearing cup start to break down/delaminate). I replaced all bearings and seals, got everything dialed in to spec (see below) and put it back on the road. Immediately I had some rough grinding noise so after a couple test drives I took it back out and got it on the bench now. I found that the spider gears were binding up and getting ground down. When I rebuilt it I did not take the spider gears out or remove the ring gear, I left the carrier assembly intact. I can't figure what would have caused an issue with the spider gears, or whether these gears can be saved or if I need new ones? Any ideas or suggestions is much appreciated.

Here are the specs from the initial rebuild:

Pinion rotational torque at 20 in-lbs
Ring gear backlash 0.007"
Rotational torque with carrier installed 25 in-lbs
Gear pattern in the middle between toe and heel on drive and coast side, not meshing overly deep (backlash looked good).

 

[2WheelWillie]

How many miles do you have on the diff? I wonder, if the output bearings are starting to fail do to delaminstion, it is possible other bearings and surfaces are also compromised, out of tolerance. Which bearings did you change?

I just replaced my front diff. 2017 XLT with 188,000 miles. Used car dealer replaced it with used unit which lasted 24,000 miles. I could hear a hum and suspected front diff unfortunately I was 80 miles past my 24,000 mile powertrain warranty. I had the transmission serviced by a local reputable transmission and powertrain shop. They identified the front diff as the source of the noise and recommended replacement. When asked they said they could rebuild it however they only warrantied there rebuild for 12 months/12,000 miles and expected a the rebuild to be within several hundred dollars of a 3yr/36,000 mile warranty remanufactured unit. They suspected delamination of the bearings.

I opted to source my own remanufactured front diff with 3yr/36,000 mile warranty from U.S. Powertrain https://www.uspowertrain.com/ $1500 shipped. They did not have a unit ready to go but had one in inventory ready for rebuild. 2 day s to build, shipped out on the 3rd day and was delivered to another trusted shop I use. One thing to know is U.S. Powertrain requires the diff to be installed by a shop for warranty purposes. This was not an issue for me as I simply didn't have the time or space to pull the diff and swap it. $600 for the install, so in total I am in for $2100.00. Wish I had the space and time but this is life.

 

[PlorkZ47]

@2WheelWillie Thanks for all the info, I have 124k miles on it, certainly not expecting this kind of issue. I replaced all bearings including the output shaft bearings. The initial issue was a carrier bearing badly pitted/delamination, I’m wondering if the spider gears/side gears were wearing out then too, I just didn’t check the spider gears first time around.

After what I was seeing in the diff and not wanting to go in another $200 to $300 for a set of gears I decided to look for a rebuilt unit. Like you I also found US Powertrain, they didn’t have a rebuilt unit but had a brand new unit ready to go so I have that on the way. Now I’m hoping this new unit isn’t new stock with the same bad bearings as all these diffs off the assembly line.

Thanks for your tip about having to get a shop to install it, I just chatted with their support staff and they said I can install it myself so maybe they recently changed their policy.