im looking at buying a 1990 F superduty with a zf-5. I went and drove it a couple days ago. Everything seemed fine until I shifted into 4th, the whine got a little louder from the normal zf sounds. Even with the clutch pushed in I still heard it and after it started I slowed down and shifted into 3rd and it was still there, shifted through 4th to 5th and still there, then went away for a min then came back. Got back to the guys house and he said he replaced the seal on the back of the zf but it was leaking. It needs a new u joint in the rear so that had a little clunk.

So in all I'm wondering if this sounds like a trans problem or if it could be a throw out bearing or carrier bearing? The truck only has 74,000 miles on it

thanks
Lloyd