Odd sound after PTU replaced

[JEDinMD]

PTO made unusual whirring sound upon decelerating near 30 mph . Replaced under warranty. Now odd sound upon acceleration at 5 - 10 mph, goes away after a few seconds. After traveling at least 30 minutes, unable to hear sound. Can be heard again after next day from cold start. And so it goes day after day. Service visit this week. Any ideas?

 

[jo7hs2]

Can you describe or have a passenger record the sound?

 

[JEDinMD]

Sounds like gears meshing is trying to mesh. Not very loud and only through about 25-30 mph.

 

[jo7hs2]

Never noticed it before the PTU was changed, right?

I ask because some units of the 6F transmissions have some final drive gear whine, particularly the 6F35, but since the designs are fairly similar I guess it could show up in a 6F50/55. It’s usually only heard in first or second gear though, which is a bit low for those speeds. Interesting, it is only a bit below the speed the RDU usually disengages unless under hard acceleration, so it is when the PTU is under load during the acceleration part of the system’s program.

 

[peterk9]

PTO made unusual whirring sound upon decelerating near 30 mph . Replaced under warranty. Now odd sound upon acceleration at 5 - 10 mph, goes away after a few seconds. After traveling at least 30 minutes, unable to hear sound. Can be heard again after next day from cold start. And so it goes day after day. Service visit this week. Any ideas?

The Explorer has a PTU (Power Transfer Unit). It doesn't have a PTO.

Peter

 

[JEDinMD]

Never noticed it before the PTU was changed, right?

I ask because some units of the 6F transmissions have some final drive gear whine, particularly the 6F35, but since the designs are fairly similar I guess it could show up in a 6F50/55. It’s usually only heard in first or second gear though, which is a bit low for those speeds. Interesting, it is only a bit below the speed the RDU usually disengages unless under hard acceleration, so it is when the PTU is under load during the acceleration part of the system’s program.

Correct, exactly as you described. Never heard it before PTU/PTO replaced. And it usually cannot be heard again after the vehicle has traveled for 20-30 minutes and is at ordinary operating temperature. Should I be concerned? Regarding PTO vs PTU: Ford identifies it as a PTO on the vehicle work order/service invoice. Just using the terms provided to me. Thanks all!

 

[jo7hs2]

Correct, exactly as you described. Never heard it before PTU/PTO replaced. And it usually cannot be heard again after the vehicle has traveled for 20-30 minutes and is at ordinary operating temperature. Should I be concerned? Regarding PTO vs PTU: Ford identifies it as a PTO on the vehicle work order/service invoice. Just using the terms provided to me. Thanks all!

I’m not sure I’d be concerned yet, but I would have the dealer check it out. It’s entirely possible that you are just paying more attention to the noises it makes since the PTU was replaced, and it’s always made the noise to some degree, and it’s also possible some gear noise is acceptable and not indicative of a problem. I’d still have them check it, particularly if the vehicle is still under powertrain warranty.

 

[peterk9]

Correct, exactly as you described. Never heard it before PTU/PTO replaced. And it usually cannot be heard again after the vehicle has traveled for 20-30 minutes and is at ordinary operating temperature. Should I be concerned? Regarding PTO vs PTU: Ford identifies it as a PTO on the vehicle work order/service invoice. Just using the terms provided to me. Thanks all!

Bottom line is that you should not be able to hear the PTU at all. As suggested, have the dealer check it out again.

Peter

 

[JEDinMD]

Thank you, jo7hs2 and Peter. Goes to the dealer tomorrow AM - still under powertrain warranty. Will be asking service advisor to ride along to listen for the sounds we hear. Will post results/next steps. Again, thank you.

 

[JEDinMD]

Sound heard by service advisor when he rode along with me this morning and by mechanics, too, but they cannot localize. Service advisor and I agree that it sounds like it's coming from the left/driver side. They are wondering if it's something with the exhaust system. I would expect to hear the sound when the vehicle is revving but stationary, but that is not the case. It is only heard when it moves from a dead stop and at or near the first few upshifts. They will be using an instrument tomorrow to try to localize the sound. The exhaust system is largely passive, yes?

This all started with a leaking oil seal in the PTO/PTU.
1. Oil seal replaced.
2. Unusual whirring sound heard upon deceleration starting at about 35 mph - reported promptly to dealer.
3. Dealer replaced PTO/PTU.
4. New, latest sound is heard.
5. Dealer seeking source of sound - awaiting results.

All within about 1 month.
Powertrain is still under warranty.

Please share your thinking with me. Thanks.

 

[jo7hs2]

Sound heard by service advisor when he rode along with me this morning and by mechanics, too, but they cannot localize. Service advisor and I agree that it sounds like it's coming from the left/driver side. They are wondering if it's something with the exhaust system. I would expect to hear the sound when the vehicle is revving but stationary, but that is not the case. It is only heard when it moves from a dead stop and at or near the first few upshifts. They will be using an instrument tomorrow to try to localize the sound. The exhaust system is largely passive, yes?

This all started with a leaking oil seal in the PTO/PTU.
1. Oil seal replaced.
2. Unusual whirring sound heard upon deceleration starting at about 35 mph - reported promptly to dealer.
3. Dealer replaced PTO/PTU.
4. New, latest sound is heard.
5. Dealer seeking source of sound - awaiting results.

All within about 1 month.
Powertrain is still under warranty.

Please share your thinking with me. Thanks.

Maybe they put something back together wrong in the exhaust? They had to move it out of the way to replace the PTU. I’d expect the noise to be engine RPM rather than vehicle speed dependent if it was exhaust related, but who knows. I’d reserve judgment until they scope out the sound better. The good news is that they HEARD it.

 

[JEDinMD]

Maybe they put something back together wrong in the exhaust? They had to move it out of the way to replace the PTU. I’d expect the noise to be engine RPM rather than vehicle speed dependent if it was exhaust related, but who knows. I’d reserve judgment until they scope out the sound better. The good news is that they HEARD it.

Appreciate your reply and remarks about having to move the exhaust system out of the way. Yes, very glad they heard it (the service advisor heard the first sound (whirring) and then this latest sound, too. Very grateful that he heard what we heard both times! Hopefully we'll know more tomorrow. Thank you.

 

[JEDinMD]

Sound localized to the catalytic converter. Replacement pending part availability.

 

[Lincolnunit]

Sound localized to the catalytic converter. Replacement pending part availability.

Was this confirmed? I'm hearing the same thing at about 3000 RPM under load. After a PTU change I was hearing this strange noise not coming from the engine but beneath me. Almost like a faint rattle for a second at 3000 RPM