Rear differential replacement

[Joseeevelez]

Hey guys it’s Jose here with a 2019 mustang GT. I’ve been hearing grinding noise from my rear end lately. I took it to ford and it turns out that the rear diff is gone & needs to be fixed. They wanted to rebuild it but the parts alone cost 2300 dollars plus labor which is 1500. The total coming out to 4300. I was wondering if there is better options out there? If im correct I saw that I can buy a new diff from American muscle for 1200. Please correct if I’m wrong. I’m not too familiar with this kind of stuff. Thank you guys!

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[blacksheep-1]

I see your from Arizona, was hoping Fla or PA, ( Kohr Performance or Phoenix) I don't know anyone who could help you in Arizona, but I'm sure there's a member here that could help you. That $1200 sounds pretty righteous, would you get to choose a gear ratio with that?
Building your own diff gives you several options, gear ratio for one, the type of limited slip is another ( think Torsen here), and pulling all of that out will allow some suspension upgrades as well.
This is of course if you have someone in mind, or can at least do the removal or install yourself. Just some things to kick about.

 

[JDee]

I have an MMR diff cooler kit that I want to sell, you might want to look into that for your diff. The diff will last much longer with a good cooler. I just unloaded my '16 because the Torsen packed it in and I was tired of spending money on an old car.

 

[Joseeevelez]

Sorry for the late response guys! Thank you guys for hitting me back up. I’m in the process with ford trying to get warranty coverage. They said I still may need to pay a small portion of that 4300. But depending on how much I have to pay, I might just get an upgraded diff if it’s gonna be the same for the stock.

 

[Joseeevelez]

Hey guys I’m back with an update on the rear diff. Ford did not end up rebuilding the differential. Ford said it was the side case bearings on both sides that was making the grinding noise and wasn’t the gears or anything. They replaced only the bearings and said the grinding was gone. My first mistake was not taking it on a test drive on the highway. I noticed the noise this morning on my way to work & it’s still whining. Just not as loud. Are differentials supposed to be quiet & am I being paranoid or did ford just mess up? They didn’t even give the option to still go with rebuild like we intended to do. They just replaced the bearings and called me when everything was done. Here’s the summary they left for the work they did. Thanks guys, I appreciate if anyone can give some advice. I’m still taking the car back to ford today

 

[302BOB]

I'm no mechanic, by ANY means, but it surely sounds, in more ways than one that they need to re-assess what's going on with your car..........as you well know, dealers often look for the least expensive way to "help" a customer.....Good luck..............................

 

[Joseeevelez]

I'm no mechanic, by ANY means, but it surely sounds, in more ways than one that they need to re-assess what's going on with your car..........as you well know, dealers often look for the least expensive way to "help" a customer.....Good luck..............................

Yeah I will. I called ford and talked to my service advisor and let him know of the issue. I told him I will be there today & will test drive the vehicle with him so they know exactly what what I’m hearing so that’s there no miscommunication. I’m just livid that they didn’t just do the rebuild & give me the option instead of just going the cheap route to save a buck. Now I’m down a vehicle for most likely another week or so.

 

[Joseeevelez]

I took it to ford. I drove the service and a technician. They both heard that humming sound & the tech said that it’s “normal” for a 8.8 ring & pinion gear. It’s covered under A 1 year warranty. Should I take it to get a second opinion? I’m not sure what do to

 

[Joseeevelez]

I took it to ford. I drove the service and a technician. They both heard that humming sound & the tech said that it’s “normal” for a 8.8 ring & pinion gear. It’s covered under A 1 year warranty. Should I take it to get a second opinion? I’m not sure what do to

They also that the gears in the diff itself were completely fine. That the two bearings on the sides were bad & that’s what they replaced.

 

[xr7]

With that much crap in the diff just putting in carrier bearings is a crap "repair". If the carrier bearings are that bad the ring and pinion gear pattern is wrecked, the pinion bearings are junk.
I worked at several dealerships, GMC, Ford & Volvo, all trucks, Class 8's to light duty, I would never had done this type of repair.

 

[blacksheep-1]

8.8s tend to be one of the noisier diffs, but go out and test drive a new car and tell me they sound the same... I doubt they will. If you don't get some satisfaction, Ford has a 1 800 number for customer complaints that you might try.

 

[Joseeevelez]

8.8s tend to be one of the noisier diffs, but go out and test drive a new car and tell me they sound the same... I doubt they will. If you don't get some satisfaction, Ford has a 1 800 number for customer complaints that you might try.

With that much crap in the diff just putting in carrier bearings is a crap "repair". If the carrier bearings are that bad the ring and pinion gear pattern is wrecked, the pinion bearings are junk.
I worked at several dealerships, GMC, Ford & Volvo, all trucks, Class 8's to light duty, I would never had done this type of repair.

Thank you guys. I scheduled another appointment at a different ford dealership to get a second opinion. They said that the diff shouldn’t be making any type of humming noise that I’m describing. It won’t be til the 31st to get it looked at again so I guess I’ll just be test driving the vehicle til then. I’ll also check the fluid to see if it turns glittery like it did the first time. I hope it does get contaminated with metal shavings again so I can shove it in fords face that they did a horrible job & lied about it be completely “normal”. I also hope it doesn’t so I can not worry about being down a vehicle. I appreciate all the information guys!

 

[TMSBOSS]

It may help a bit with perspective to keep in mind that ”Ford” provides the parts and to a point, technical advice for the repair. The eyes and hands doing the repair and assessing the problem are from the dealership. Some may say a difference without a distinction, not really.
I’m interested in seeing what the different dealership tech staff finds.
Yes, the 8.8 by nature, especially with 3.73 gears is noisy. Why the dealership didn’t replace all the bearings as a minimum, gear set also, is a mystery.

 

[EF1]

It may help a bit with perspective to keep in mind that ”Ford” provides the parts and to a point, technical advice for the repair. The eyes and hands doing the repair and assessing the problem are from the dealership. Some may say a difference without a distinction, not really.
I’m interested in seeing what the different dealership tech staff finds.
Yes, the 8.8 by nature, especially with 3.73 gears is noisy. Why the dealership didn’t replace all the bearings as a minimum, gear set also, is a mystery.

I hear everyone say the 8.8 is noisy with anything above 3.73 gears. Mine came with 3.55 gears and it was quiet. I swapped to a Detroit Truetrac and 4.10’s. It is as quiet as the stock set up. I have a stick axle. Is the IRS in the S550 inherently noisier?

 

[blacksheep-1]

I hear everyone say the 8.8 is noisy with anything above 3.73 gears. Mine came with 3.55 gears and it was quiet. I swapped to a Detroit Truetrac and 4.10’s. It is as quiet as the stock set up. I have a stick axle. Is the IRS in the S550 inherently noisier?

I would say no. The faster you spin the ring n pinion, the more opportunity there is to make noise, but a good setup shouldn't really be any noisier than stock. Compared to a 9inc, the old 8 inch or a GM 10 or 12 bolt, it tends to be a bit noisier, but only if you listen real well, not a huge deal.