'18 3.73 PP Diff whine

[HourlyB]

So, finally got the her into the shop, they changed out the gears, bearings and fluid and the noise is gone!


The bad news is that now, the car has a low vibration at 40 mph. Remains when taken out of gear. Seems to increase with speed, but not dramatically.

This makes me think (THINK) that it's a wheel issue, but is there anything else that could be causing it related to the rear end? (I'm sure there is something)

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[Ehdrian]

So, finally got the her into the shop, they changed out the gears, bearings and fluid and the noise is gone!


The bad news is that now, the car has a low vibration at 40 mph. Remains when taken out of gear. Seems to increase with speed, but not dramatically.

This makes me think (THINK) that it's a wheel issue, but is there anything else that could be causing it related to the rear end? (I'm sure there is something)

It is possible they changed the orientation of the drive shaft? I think they're balanced from the factory and need to be re-installed exactly the same way.

 

[Ehdrian]

My 2015 GT PP 2.73's actually had a gear whine, similar to what you were reporting from the factory. Ford had the dealership rebuild it during the first year of ownership. Haven't had any issues since.

 

[HourlyB]

They put the car on the lift and spotted some movement in the driveshaft while it rotated.

So, they replaced the U-joint in the driveshaft, and the vibration was still there. They put it up on the lift, and couldn't spot anything in the driveshaft anymore, but they noticed the right rear wheel was moving, so they thought it was a dent. (Also they didn't charge me for the work, so that's a plus!)

So I went to a wheel repair place, they said that it looked like it was a small dent, they fixed it and...

Vibration is still there. Same location, same intensity. Which to me spells wheel bearing, or it's possibly still in the driveshaft.

Honestly should I just take it to a Ford dealer and eat the $300 diagnostic fee?

 

[HourlyB]

One thing I did notice, that I just remembered, was that I had some rear break "stickage" pulling into the shop, i even saw a bit of smoke coming from the left rear wheel well.
Could that be related?

 

[Brazos609]

How has nobody in five pages asked if the wear pattern was checked at any time for diagnosis?

 

[shogun32]

How has nobody in five pages asked if the wear pattern was checked at any time for diagnosis?

'cause shade-tree mechanics? We're all about as useful as Wilson hiding his shnoz behind the board fence...

 

[HourlyB]

How has nobody in five pages asked if the wear pattern was checked at any time for diagnosis?

If you're talking about tire wear pattern, the tires got rotated before the rear end job happened, and they looked fine.

 

[Brazos609]

If you're talking about tire wear pattern, the tires got rotated before the rear end job happened, and they looked fine.

https://www.google.com/amp/s/www.racingjunk.com/news/how-to-set-up-your-rear-gear-correctly/amp/

You use marking paste to check and verify that the ping and pinion are properly set up.

 

[K4fxd]

How has nobody in five pages asked if the wear pattern was checked at any time for diagnosis?

On the S550 mustang you have to remove the diff from the car to check it.

 

[Brazos609]

On the S550 mustang you have to remove the diff from the car to check it.

He had two different complete differentials that were installed, the wear pattern should have been checked on both before install and he had all the bearings replaced at least once. The differentials have been out multiple times presenting opportunities to check the wear pattern.

 

[K4fxd]

He had two different complete differentials that were installed, the wear pattern should have been checked on both before install

The first one was a simple pinion swap. That was screwed up or the gears were worn out. I agree if you are going to swap pinions you should also install a new crush sleeve, which involves removing the whole guts of the diff. At that point the wear pattern should have been tested. But careful measurements before disassembling would have made the wear pattern a safety check.

Since I wasn't there on the initial install all this may have been done.

I rebuilt a 8 3/4 mopar and had everything looking perfect, it vibrated your teeth out above 60 mph. I never could figure out why. A new pumpkin with new gears fixed it.

 

[HourlyB]

https://www.google.com/amp/s/www.racingjunk.com/news/how-to-set-up-your-rear-gear-correctly/amp/

You use marking paste to check and verify that the ping and pinion are properly set up.

The shop says they checked that on the install, but it still whined after install.

He had two different complete differentials that were installed, the wear pattern should have been checked on both before install and he had all the bearings replaced at least once. The differentials have been out multiple times presenting opportunities to check the wear pattern.

I only had one diff installed.

After the 3.73 pp diff was installed, it made a whining noise. No real large vibration through the steering wheel or seat, but you could feel the vibration if you held the shifter.

So, I got the gears and the bearings replaced. Now it has stopped making the whining noise, but it has started making the noticable vibration that comes on at around 40 mph. And I'm not talking about how it was a week or two later it started, I mean immediately after the work was done.

Other people have reported similar problems involving a the driveshaft, and the solution being a stainless steel hose clamp to rebalance it.

Outside of the shop reinstalling it incorrectly, I can't see how my diff getting new gears and bearing unbalances my driveshaft.

 

[HourlyB]

Put the car on jacks and recorded it, figured showing was better than vaguely describing;

 

[HourlyB]

Took it to a Ford Dealer, and they said it was symptomatic of SSM 47991, which says the drive pinion flange was likely installed correctly. They said I should head back to the shop and get it checked out, printing out the diagnosis.

So I did, and they ended up seeing that a nut was installed out of alignment. They realigned it, and handed it back.

Mustang is still making noise. It might've gotten quieter, but it's definitely still there.

The only small thing it might be is that when I got my wheel repaired, they pumped the tire to 40 psi, and I took it down to 30. So, the wheel might be unbalanced. I've already got a appointment for both the rears to get rebalanced. If it does fix it, great! If it doesn't, at least I am fixing something.

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