Rear End Failure

[hbalek]

I'm wondering if this is some kind of alignment issue (or rather misalignment) of the drive shaft , diff mounts, etc, basically everything connected to the diff. Unless you won the worst lottery and got two terribly defective rear diffs I'm at a loss. Where the bearings screwed at all, which could/would cause such issues.

Misalignment of the driveshaft to the diff would cause vibrations, noise, premature failure, wear, etc

I specifically asked my service department to check my driveshaft after 2 failed PTU's and RDU's. They found nothing with that but said the RDU had the wrong gear ratio. Mine is driving great now after a 4-wheel alignment and proper gear ratio differential.

 

[musclecarman39]

My rear differential and transfer case/ptu were replaced back in early June at about 50,000 miles. The transfer case failed again just 3 months later. I think the differential is bad again too.

Just had my rear diff replaced again for a howling noise at 45 mph. My 21 has 35,000 miles on it. Only had 700 miles on the 1st rear diff replacement. Picked it up from the dealership, had a very bad vibration, jerking and "bucking". Took it back and now the transfer case is being replaced...wth

 

[cheetoduster]

I specifically asked my service department to check my driveshaft after 2 failed PTU's and RDU's. They found nothing with that but said the RDU had the wrong gear ratio. Mine is driving great now after a 4-wheel alignment and proper gear ratio differential.

They put a diff from a 2.3L Explorer in your ST because they didn't know the difference. Probably a good thing the two have different gear ratios, if they were the same the service dept probably would have sent you on your way with the smaller diff.

 

[enphor]

Just had my rear diff replaced again for a howling noise at 45 mph. My 21 has 35,000 miles on it. Only had 700 miles on the 1st rear diff replacement. Picked it up from the dealership, had a very bad vibration, jerking and "bucking". Took it back and now the transfer case is being replaced...wth

Maybe another case of them installing a diff type with the wrong "ratio". I can see that messing up the PTU, things not spinning at the right speeds when the vehicle mechanical and electrical systems expect them to be pushing things to the point of failure.

Mental note , if I ever need a new rear diff, give them the exact part number for the ST!

 

[musclecarman39]

Maybe another case of them installing a diff type with the wrong "ratio". I can see that messing up the PTU, things not spinning at the right speeds when the vehicle mechanical and electrical systems expect them to be pushing things to the point of failure.

Mental note , if I ever need a new rear diff, give them the exact part number for the ST!

That's what I was thinking too. I'm definitely going to have them check to make sure it's the correct rear diff.

 

[jwuonog]

I specifically asked my service department to check my driveshaft after 2 failed PTU's and RDU's. They found nothing with that but said the RDU had the wrong gear ratio. Mine is driving great now after a 4-wheel alignment and proper gear ratio differential.

Glad to hear you're back up and running. What dealership did you go to? Do you have any mods?

 

[hbalek]

Glad to hear you're back up and running. What dealership did you go to? Do you have any mods?

I have no mods at all and I went to Sheehy Ford in Gaithersburg, where I bought it 5 years ago.