My automatic diesel P38 is whistling quite audibly when accelerating in drive. This doesn't really happen in neutral. My husband who's a mechanic thinks it could be the transfer case, I was thinking maybe the turbo? I know on M51 engines turbos tend to need replacing frequently, I swapped mine a year ago with another used one. We frequently check that there's enough oil in the transmission. But what do you guys think? I can't pinpoint where it's coming from. I attached a short YT video of the sound where I was turning in a junction and accelerating.

Split turbo hose or intercooler would me my bet. Never heard of turbo's needing replacing frequently, I have one on 147K miles and another on over 240K kilometers.

Datatek said:

Split turbo hose or intercooler would me my bet. Never heard of turbo's needing replacing frequently, I have one on 147K miles and another on over 240K kilometers.

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Thanks for your response. So you don't think it sounds like the transfer case? The whistling changes frequency along with shifting gears, you can hear it at the end of the video a bit.

feyniriel said:

Thanks for your response. So you don't think it sounds like the transfer case? The whistling changes frequency along with shifting gears, you can hear it at the end of the video a bit.

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Hard to tell, but I think turbo hoses are the easiest to check and most likely cause. I assume there is oil in the transfer case?

Datatek said:

Hard to tell, but I think turbo hoses are the easiest to check and most likely cause. I assume there is oil in the transfer case?

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Yes, there is. We'll try to check them.