1986.5 D21, Z24i, 2wd, manual, 220K. Son came home saying there was a knocking sound coming from the engine. Took it for a drive and it's not the engine. No odd sounds coming when the clutch is depressed. However, in neutral I can hear a faint knock. Hard to hear when you rev the engine. When in gear, no problem hearing it. It changes with speed as long as there's a load on it. Back off the gas or press the clutch and it almost vanishes. It's loudest in 3rd gear. It shifts normally and he says he didn't have any trouble shifting.
Crawled underneath to have a look and discovered the carrier bearing was toast. I mean like Texas toast. Had at least 3/4" lateral play with the boots almost completely gone. So had to pause and fix it since I can't leave my truck on jacks for too long.
Sadly, but not unexpectedly, the problem persists. Laying underneath, you can hear the knock better. Still slight in neutral, hard to tell if it's rpm dependent, goes away when you depress the clutch. I put my hand on the trans and can feel the beat.
So I'm thinking, it's not the clutch/throw out bearing since it's waaayyy worse in 3rd gear. Not the output shaft since it does it when not moving. Input shaft? Bearing or 3rd gear?
Gonna drain the oil and look for metal. Honestly, it probably doesn't matter. Looks like the old girl is heading to the great scrap heap in the sky.
We are the original owners so this is a sad day.