I have a 96 D1 that is making a high-pitched squeal at when cruising at 20-40 mph, or anytime I ease up on the gas while in gear. It will not make the noise if I let off the gas completely, but will if I ease up but keep my foot on it.
I cannot pinpoint the noise since I have to be in motion to make it. It does appear to be coming from the center or right of center of the vehicle, forward of the passenger compartment.
I will be checking the U-joints as soon as I can, but any other guesses? From my searches, it seems that the U-joints typically make their noise while someone is getting on the gas pedal.

Thanks in advance,

 

Perhaps a belt squeal, from a bearing that is starting to sieze up; or a very good vac leak. One clever suggestion a few days ago from a Rover pro was to disconnect MAF air hose (big) from air box, and shove an oil filter or similar size can in there and clamp it.. Then the vac leak will be max, and make quite a noise. Maybe vac line from intake plenum to valve cover, there is a baffle in there that needs to be cleaned from time to time (kinda like an old PCV).

Not to be confused with transfer case whine. You should be able to simulate a vac leak or belt squeal while parked, just rev up engine.

 

Mine squeals a little at idle, which I think is the power steering pump. Doesn't always do it, and when it does if I increase rpm's even slightly it stops squealing. Some dude in the parking lot at Advance Auto walked up to me one day when it was doing that and insisted I had a bad vacumn leak in one of the cylinders, but I'm pretty sure he was wrong.

I think it is the power steering pump, possibly a bearing in there.

 

Maybe vac line from intake pleum to valve cover, there is a baffle in there that needs to be cleaned from time to time (kinda like an old PCV).

What is involved in cleaning it?

 

My squeal only happens in motion and in gear.

 

1982 Porsche 928

What a sweet car, I had a 86.5 Porsche 928. What a blast to zip around curvy back roads. Made going to work real fun.

 

Not much, just remove the hose from the passenger valve cover, pull out the oil separator, clean with carb cleaner, put it back, done.
Do this every 6 months.

 

I did not realize he was talking about the oil separtor. Thanks Spike.

 

For Danny Lee - see Oil Separator - Valve Cover | Land Rover Engine Parts at RoverParts.com, you pull it out carefully with needle nose, solvent clean. Just an oil baffle, but if it gets plugged, internal space PSI can rise and vent oil through front / rear crank seals.

For Robot808 - so if it won't make noise in park, no matter engine speed, that kind of leaves the drive train. Does it change if tranny slipped into "N", or in different gears? Would be checking diff fluid levels, transfer case fluid level, and greasing those zerks on drive shafts. Is the noise in sync with engine speed or vehicle speed?

 

Noise disappears when slipped into neutral. The squeaking seems to be the same pitch no matter the speed, just seems to do it at certain times, like when I just ease off the gas a little or I am cruising on surface streets.
Diff fluids should be fine, however I am doing will be greasing the zerks and checking the TC fluid this week. Wanted to do it tonight, but Chicago weather is not cooperating...