Blown rear diff - '21/ 51k mi

[jeg11010]

Took my ST in to the dealer yesterday because I could feel a pretty heavy vibration in the steering wheel while stopped but in drive or reverse. If I were to shift into park or neutral, it would go away. I figured it was something transmission related as if it were flex pipes or something else, I'd probably feel it all the time. Also when shifting in to gear, I was starting to hear and feel a pretty loud clunk. Aside from that, nothing really noticeable while driving.

Turns out my rear diff is shot and will be replaced with a new one. Got to talking to the service manager and the mechanic who looked at it and they said I'll be getting a new driveshaft also, as the driveshaft is nearly impossible to remove from the rear diff without damaging or bending it? Find it hard to believe that Ford agrees to that considering this is a warranty job, but I won't argue with that. Gear oil slung all over the underside of the car in that area. Said my oil level was nearly empty so they added some and it should be safe to drive for the next 2 weeks until the parts come in.

Does anyone know if there is anything about the new units that will prevent this from happening again at 100k mi? Has anything been redesigned? Can the 3 bolt be changed to 4 bolt? Should I get a brace? Any input would be appreciated. I have a Ford ESP that covers me to 8 years/ 100k mi but I'm starting to think it would be wise to trade up to something newer when that time comes.

 

[UNBROKEN]

There’s a specific tool needed but of course the driveshaft can be removed without damage. I would be worried about leaving my car with a shop that told me otherwise.

 

[SugarMouth]

You have a vibration while stopped in gear? Not sure how the rear diff would influence anything in that scenario. Did they explain what failed in the diff?

 

[Edubdiz]

You have a vibration while stopped in gear? Not sure how the rear diff would influence anything in that scenario. Did they explain what failed in the diff?

agreed. that doesn't make any sense whatsoever.

 

[Cruising68]

There’s a specific tool needed but of course the driveshaft can be removed without damage. I would be worried about leaving my car with a shop that told me otherwise.

This. I easily fabricated one with some square tube, an exhaust clamp, and a welder. Not sure how you could damage the driveshaft.


Sent from my iPad using Tapatalk

 

[jeg11010]

You have a vibration while stopped in gear? Not sure how the rear diff would influence anything in that scenario. Did they explain what failed in the diff?

Yes, if I stopped at a light or in traffic, the wheel (and car) would vibrate pretty badly. If I shifted to park, or neutral, it would smooth out instantly. I'm honestly not sure how that pertains to the rear. I asked exactly what went wrong inside and they just said "it blew up" and made it seem as if they've seen this more times than they can count. It seems to me like the leaky diff was obvious just by the visual and they want to start with that before digging into anything else? Unfortunately there aren't many Ford dealers in my area so I'm kind of limited.

 

[Caster]

If the dealer wants to throw lots of brand new parts at it - LET EM"!!!

 

[Cdubya]

Before I switched to 2026, my 2020 started having similar symptoms. Vibration at a stop light, especially in winter. Park or neutral or drive, it would immediately go away. It was not the engine or trans mounts. I suspect something going on in the trans. At least you get a new rear diff--these seem like they need new pinion and/or carrier bearings after 100k miles.

 

[SugarMouth]

Yes, if I stopped at a light or in traffic, the wheel (and car) would vibrate pretty badly. If I shifted to park, or neutral, it would smooth out instantly. I'm honestly not sure how that pertains to the rear. I asked exactly what went wrong inside and they just said "it blew up" and made it seem as if they've seen this more times than they can count. It seems to me like the leaky diff was obvious just by the visual and they want to start with that before digging into anything else? Unfortunately there aren't many Ford dealers in my area so I'm kind of limited.

They tell you the diff "blew up" yet say it is safe to drive for a couple weeks? Be prepared for the issue to be something other than the rear differential.