Downshift noise

[HVAC2]

Should have recorded it. Towing the ATC at about 8500lb today. Steep grades between Arcata and Sacramento. All temps are normal. When downshifting, steep uphill a very loud screeching sound and it seemed to be stuck between 5th and 4th.
Happened approx 5 times. My wife said it sounded like high pressure air noise.
Trucks been run hard but only 23000 miles. 2018 2wd. Almost always towing and in very tough conditions and I have a lead foot.
It works fine, downshifting in full exhaust brake. Only happens when under very steep grades and arguably being abused.
Your thoughts are appreciated.

 

[Wiredawg]

HVAC2,
Recommend filling in signature with all truck info like mine. Screeching doesn't sound normal for either an Aisin or 68RFE, so recommend taking it to the dealer to check out. Looks like you should still be under warranty.

Please keep us posted.

Cheers, Ron

 

[HVAC2]

HVAC2,
Recommend filling in signature with all truck info like mine. Screeching doesn't sound normal for either an Aisnin or 68REFE, so recommend taking it to the dealer to check out. Looks like you should still be under warranty.

Please keep us posted.

Cheers, Ron

Should have recorded it. Towing the ATC at about 8500lb today. Steep grades between Arcata and Sacramento. All temps are normal. When downshifting, steep uphill a very loud screeching sound and it seemed to be stuck between 5th and 4th.
Happened approx 5 times. My wife said it sounded like high pressure air noise.
Trucks been run hard but only 23000 miles. 2018 2wd. Almost always towing and in very tough conditions and I have a lead foot.
It works fine, downshifting in full exhaust brake. Only happens when under very steep grades and arguably being abused.
Your thoughts are appreciated.

2018 CTD Laramie. 2wd. 68 RFE.

 

[Tuesdak]

high pressure air noise

So your Cummins powered through the tires and lit em up?

Maybe an exhaust brake coming on combined with a leak on the exhaust side. The passenger literally would be sitting on top of the exhaust side. Look for soot marks giving it away.

On acceleration, aside of any exhaust leaks, you may have a loose clamp leaking boost. The silicone hoses make a lot of noise if they blow off or leak under significant boost. A boost leak anywhere could be noisy.

I had a 6.5TD strapped to the dyno on a dyno day out here. It didn't come in dead last. However on one pull it loudly blew it's only hose from the turbo to the intake at 24 PSI of boost. I thought the radiator blew up. The audience was running away like they were going to die! Just saying it can be loud.

One would hope the Turbo isn't it, but, the wheels rubbing the housing from bearing failure could be a source of the noise.

What stopped the noise? Did you let off the hammer and it stopped? This could have allowed a slipping transmission to stop slipping. (Static friction has higher TQ holding power than slipping/sliding friction.) Once it stops slipping it may be able to hold full power.

Trans oil level and condition ok?

 

[HVAC2]

HVAC2,
Recommend filling in signature with all truck info like mine. Screeching doesn't sound normal for either an Aisnin or 68REFE, so recommend taking it to the dealer to check out. Looks like you should still be under warranty.

Please keep us posted.

Cheers, Ron

So your Cummins powered through the tires and lit em up?

Maybe an exhaust brake coming on combined with a leak on the exhaust side. The passenger literally would be sitting on top of the exhaust side. Look for soot marks giving it away.

On acceleration, aside of any exhaust leaks, you may have a loose clamp leaking boost. The silicone hoses make a lot of noise if they blow off or leak under significant boost. A boost leak anywhere could be noisy.

I had a 6.5TD strapped to the dyno on a dyno day out here. It didn't come in dead last. However on one pull it loudly blew it's only hose from the turbo to the intake at 24 PSI of boost. I thought the radiator blew up. The audience was running away like they were going to die! Just saying it can be loud.

One would hope the Turbo isn't it, but, the wheels rubbing the housing from bearing failure could be a source of the noise.

What stopped the noise? Did you let off the hammer and it stopped? This could have allowed a slipping transmission to stop slipping. (Static friction has higher TQ holding power than slipping/sliding friction.) Once it stops slipping it may be able to hold full power.

Trans oil level and condition ok?

So your Cummins powered through the tires and lit em up?

Maybe an exhaust brake coming on combined with a leak on the exhaust side. The passenger literally would be sitting on top of the exhaust side. Look for soot marks giving it away.

On acceleration, aside of any exhaust leaks, you may have a loose clamp leaking boost. The silicone hoses make a lot of noise if they blow off or leak under significant boost. A boost leak anywhere could be noisy.

I had a 6.5TD strapped to the dyno on a dyno day out here. It didn't come in dead last. However on one pull it loudly blew it's only hose from the turbo to the intake at 24 PSI of boost. I thought the radiator blew up. The audience was running away like they were going to die! Just saying it can be loud.

One would hope the Turbo isn't it, but, the wheels rubbing the housing from bearing failure could be a source of the noise.

What stopped the noise? Did you let off the hammer and it stopped? This could have allowed a slipping transmission to stop slipping. (Static friction has higher TQ holding power than slipping/sliding friction.) Once it stops slipping it may be able to hold full power.

Trans oil level and condition ok?

So your Cummins powered through the tires and lit em up?

Maybe an exhaust brake coming on combined with a leak on the exhaust side. The passenger literally would be sitting on top of the exhaust side. Look for soot marks giving it away.

On acceleration, aside of any exhaust leaks, you may have a loose clamp leaking boost. The silicone hoses make a lot of noise if they blow off or leak under significant boost. A boost leak anywhere could be noisy.

I had a 6.5TD strapped to the dyno on a dyno day out here. It didn't come in dead last. However on one pull it loudly blew it's only hose from the turbo to the intake at 24 PSI of boost. I thought the radiator blew up. The audience was running away like they were going to die! Just saying it can be loud.

One would hope the Turbo isn't it, but, the wheels rubbing the housing from bearing failure could be a source of the noise.

What stopped the noise? Did you let off the hammer and it stopped? This could have allowed a slipping transmission to stop slipping. (Static friction has higher TQ holding power than slipping/sliding friction.) Once it stops slipping it may be able to hold full power.

Trans oil level and condition ok?

All good comments. Thank you. Will look at fluid tomorrow. All I had to do was back off and it went away.

 

[Ozymandias]

Ripping through the Tires isn't out of reach.
Especially on a steep hill.

I've done that more then once.

 

[Wiredawg]

All good comments. Thank you. Will look at fluid tomorrow. All I had to do was back off and it went away.

I think others came up with better explanations for the sound... Sorry, I got caught up in it actually being a noise from the transmission.

Happily it sounds like may not be a serious problem after all.

Cheers, Ron

 

[RammerJam]

All good comments. Thank you. Will look at fluid tomorrow. All I had to do was back off and it went away.

There used to be a saying among truckers that went something like "On the Whistle''. Or to that effect.

It referred to the high-pitched whistling a turbo makes when it's unrestricted. Are you sure you weren't hearing a really loud whistle instead of a 'screech'? And when you said, All you had to do was let up and it quit....... And then you said it felt like it was stuck between 5th and 4th......

And when it downshifts, your RPM goes up and that causes the turbo to wind up as well......

That all leads me to think it's something to do with the turbo. Very likely just a loose clamp or a blown hose.

good luck

 

[HVAC2]

Sorry gents. In a no cell area of n Cali. Fluid looks fine. I have never broke the tires loose yet! But it does seem to get stuck on downshift from 5th to 4th under load. Like in the middle. Loud screeching sound as well.
She's going into storage Friday for probably 4 months. Will take it in then as maintenance will be due.
Thanks for comments!

 

[Ozymandias]

There is a possibility that you would find codes as this transmission is monitored very closely by the ECM.