Transmission Noise

[newnissanfanatic]

I have a 1984 720 Z24 with an automatic transmission. Today I started hearing a humming, high pitched noise which I thought was the transmission not shifting so the noise was from the engine, but this was not true as I topped off the transmission fluid and the noise still exists even as the transmission shifts. The noise only occurs after 35 mph. Does anyone have any clue what this could be. The truck only has 80,000 miles on it and I am the second owner. The first owner is a neighbor of mine.

[captainzeros]

Get under your truck and check your driveshaft, on my '81 truck it's a two piece unit, and has a bearing around it that holds it straight. The 30 year old rubber in the bearing went out and it got a death wobble in the driveshaft up at speed, if I didn't replace it it would've raised hell and broken all kinds of things. This may or may not be the problem you're having, but it would be a good thing to check regardless. If you grab the driveshaft and can wiggle it around and shove it back and forth, that's your indicator.