Differential needs replacing- back order

[DarkMatterGrey]

They still use Friction modifier...when I had my 4.09s installed in my Torsen the shop did the work put the Ford Friction modifier in as it was in the Ford diffy lube that was used.

It is not required for S550 or S650 Torsens. It won't hurt and it is not already in the Motorcraft fluid that Ford sells by the quart over the counter. I can't say that it's that way if the shop or dealer have it already in bulk or use fluid from a different vendor (Amsoil, Valvoline, etc.) which may already contain some modifier. The reason some are sold without modifier is open, locking, and Torsens don't require it, only limited slip with clutches typically do.

Different question, was this on a S650 Mustang? If so, how did you reprogram the computer for that ratio so the speedometer and odometer are accurate, Forscan, Ford FDRS, other?

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[LouG]

Ford dealers, at least the ones in my area don't rebuild diffys. They wouldn't even install a ring and pinion from Ford performance.

How times have changed. But it's good way to get a diff to rebuild on the cheap I guess

 

[SSuperDave]

Ford Customer Assitance, 800-392-3673, do not get off the phone until they give you a case #. We the dealers cannot call them, but can respond to them once you have a case open. Its the next step in the process, but don't get your hopes up...

 

[gbadger]

Ford Customer Assitance, 800-392-3673, do not get off the phone until they give you a case #. We the dealers cannot call them, but can respond to them once you have a case open. Its the next step in the process, but don't get your hopes up...

Thank you

 

[John S]

Good luck, just think of the countless commercial operators without the use of their work trucks because of backordered parts. What a way to run a business.....

 

[gbadger]

Following up Ford couldn’t get a differential in 4.5 months and couldn’t give me an ETA on when. I called the service line like everyone said here. They were very helpful.

In the end, this issue along with the computer failing 4 times, Ford bought back the car. I am sad but it is what it is. They were fair and the process was painless for the most part. This was a great car when it was working.

I bought a used s550 GT that I will begin building. I just couldn’t stomach getting another s650 right now with the trust issues from this one. Off to the other forum.

 

[gdela016]

I don’t know why I’m posting this but to vent and maybe see if someone has advice. My differential is bad (massive clunking when driving) and it’s going to be replaced by warranty but the differential has been in back order for 2 months.

Is this common? It seems crazy Ford can’t get a differential out for a car in two months. Do they not get to use the same ones that go to making cars?

Is there no escalation point to Ford? Anyone dealt with this? They can’t even give an estimated time when they will be off back order.

I have a 2025 Darkhorse and it’s going through this same issue. My car has been at the dealership since mid July. The rear differential has been on back order for months. I called Ford again and they told me that the previous 2 times it left Michigan, it made it to Memphis where it disappeared twice. Finally got the part in and perhaps get my car back this morning.

 

[LouJay99]

Iv'e had a similar clunking issue too. They replaced the differential and it made everything way worse. It was making a loud groaning sound when turning and my steering has a really loud squeaking sound when turning. Its back in the garage and they said that the dealership fitted a different differential to what is listed for my vehicle. Mine is a dark horse, so im not sure what they fitted to it.
Would an incorrect diff being fitted cause any other issues?

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