'18 3.73 PP Diff whine

[spaz mk will]

Hmmm, if it's that, I should probably take it to the shop I got the work done at.


So, negative terminal off for half a hour and then back on? Any other processes I should do?

Other than jotting down notes on any settings you like in your dash etc, should be straightforward. Then go for a longer drive to give it time to relearn etc. I’ve not done this myself, haven’t needed to, but it’s what I’ve read here from others. Could also search KAM reset if you’re interested in more feedback.

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[HourlyB]

Other than jotting down notes on any settings you like in your dash etc, should be straightforward. Then go for a longer drive to give it time to relearn etc. I’ve not done this myself, haven’t needed to, but it’s what I’ve read here from others. Could also search KAM reset if you’re interested in more feedback.

I'm guessing I should also change the ratio on the BCM via forscan as well?

Also, if I need to adjust the pinion gear via the input flange, I assume they will need to remove it to make sure the ring and pinion are aligned correctly.

 

[Brian@BMVK]

Does a KAM reset apply here? The car should not have issues with that ratio but the computer is still expecting/calculating against the old ratio, might explain it pulling power. Pull battery for 30 minutes, unless you have a tuner with that option, this will clear the map.

Pretty sure KAM reset/unplug for 30 mins doesn't apply to something hard coded into the PCM and BCM programming, but could be.

For the whine, since you had the flange exchanged, that indicates for almost certainty that it needs adjustment of the pinion nut.

 

[HourlyB]

Pretty sure KAM reset/unplug for 30 mins doesn't apply to something hard coded into the PCM and BCM programming, but could be.

For the whine, since you had the flange exchanged, that indicates for almost certainty that it needs adjustment of the pinion nut.

Gotcha, if it needs to bring it to a shop to get adjusted, will I need to buy another two quarts of diff oil or can the old fluid be removed and added back after it's alligned?

 

[shogun32]

Gotcha, if it needs to bring it to a shop to get adjusted, will I need to buy another two quarts of diff oil or can the old fluid be removed and added back after it's alligned?

if you don't know the history of the current fluid, replace it. It's what $35?

 

[K4fxd]

For the whine, since you had the flange exchanged, that indicates for almost certainty that it needs adjustment of the pinion nut.

You really need to change the crush sleeve when changing pinion flanges.

 

[JeremyPro5.0]

If the gears whine after being installed, they were installed incorrectly.

Any competent shop should be able to set them up correctly with proper backlash and pattern so no whine and a very long life would result.

1. Go to a shop that knows what they are doing.
2. Stop driving or you will ruin the gearset. Once a pattern is worn / honed into the gears, they are done.
3. Whine is vibration, noise will happen well before anything is felt.

 

[HourlyB]

if you don't know the history of the current fluid, replace it. It's what $35?

I do know it, BG Ultra Guard 75W-90 was added into the dry diff upon installation. Whether or not it's been ruined yet is anyone's guess.

And $70, since 2 quarts are needed.

If the gears whine after being installed, they were installed incorrectly.

Any competent shop should be able to set them up correctly with proper backlash and pattern so no whine and a very long life would result.

1. Go to a shop that knows what they are doing.
2. Stop driving or you will ruin the gearset. Once a pattern is worn / honed into the gears, they are done.
3. Whine is vibration, noise will happen well before anything is felt.

The entire diff pumpkin was installed, not just the gears. The only thing done to it was changing the input flange and filling it with fluid, since the diff was off a 2018 Mustang GT PP and my Mustang is a 2016 standard GT. Unfortunately, I've already driven ~150 miles with the noise. Should I just buy a new 3.73 gearset?

 

[Brian@BMVK]

I do know it, BG Ultra Guard 75W-90 was added into the dry diff upon installation. Whether or not it's been ruined yet is anyone's guess.

And $70, since 2 quarts are needed.

The entire diff pumpkin was installed, not just the gears. The only thing done to it was changing the input flange and filling it with fluid, since the diff was off a 2018 Mustang GT PP and my Mustang is a 2016 standard GT. Unfortunately, I've already driven ~150 miles with the noise. Should I just buy a new 3.73 gearset?

It's probably just not torqued correctly.

 

[HourlyB]

It's probably just not torqued correctly.

Any idea how bad the damage might be?

 

[Brian@BMVK]

Any idea how bad the damage might be?

Likely none. May need a new nut but probably just need to have it done to spec.

 

[K4fxd]

Without replacing the crush sleeve you must take a before drag torque reading and then tighten the pinion nut to that exact spec. It is easy to overshoot it.

The proper way to replace pinion flanges on the 8.8 super (and any crush sleeve diff) is to replace the crush sleeve. However on the 8.8 super (IRS) you have to remove the gears to change the sleeve. So lots of shops just try to get the drag torque correct. Lots quicker, but more room for error.

At this stage there is no way to correctly read the factory drag torque so the crush sleeve needs replacing. There is no guarantee this will stop the whine. In my experience when they start making noise it is usually too late to fix it.

That said tightening it 10 degrees won't hurt and might help.

Back in the day used car lots would add saw dust to differential oil. This would stop the whine long enough to sell the car.

 

[JeremyPro5.0]

I do know it, BG Ultra Guard 75W-90 was added into the dry diff upon installation. Whether or not it's been ruined yet is anyone's guess.

And $70, since 2 quarts are needed.

The entire diff pumpkin was installed, not just the gears. The only thing done to it was changing the input flange and filling it with fluid, since the diff was off a 2018 Mustang GT PP and my Mustang is a 2016 standard GT. Unfortunately, I've already driven ~150 miles with the noise. Should I just buy a new 3.73 gearset?

Like I said above, get it to a good shop. They should be able to guide you.

Don’t expect a bunch of opinions on the internet to fix it at this point.

150 miles may or may not be the end of the gears. Again take it to a good shop.

 

[HourlyB]

Likely none. May need a new nut but probably just need to have it done to spec.

Gotcha

Without replacing the crush sleeve you must take a before drag torque reading and then tighten the pinion nut to that exact spec. It is easy to overshoot it.

The proper way to replace pinion flanges on the 8.8 super (and any crush sleeve diff) is to replace the crush sleeve. However on the 8.8 super (IRS) you have to remove the gears to change the sleeve. So lots of shops just try to get the drag torque correct. Lots quicker, but more room for error.

At this stage there is no way to correctly read the factory drag torque so the crush sleeve needs replacing. There is no guarantee this will stop the whine. In my experience when they start making noise it is usually too late to fix it.

That said tightening it 10 degrees won't hurt and might help.

Back in the day used car lots would add saw dust to differential oil. This would stop the whine long enough to sell the car.

Still, they had the car for a while, tho they did a lot of work besides the diff. Not sure if I can argue that they should've foreseen this issue, but they said they have done a ton work like this before.

Like I said above, get it to a good shop. They should be able to guide you.

Don’t expect a bunch of opinions on the internet to fix it at this point.

150 miles may or may not be the end of the gears. Again take it to a good shop.

Not many good shops up here. ACS racing, the closest to me, is busy until June. Forte's Parts got decent reviews and everyone I talked to said they were on the up-and-up.

 

[K4fxd]

I have no idea if they did the job properly or not. I was just putting out the correct procedure.

Sometimes crap happens.

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