Here is the link, with pictures.
http://www.gmsquarebody.com/forum/showthread.php?t=2339
Edit: Finding more pictures I have.
Back of the transmission.
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This is the bearing retainer that holds the input shaft bearing in place and doubles as what the throwout bearing rides on. All the ones I had on hand had grooves worn in them from the bearing spinning on the shaft so to play it safe I ordered a new unit for about 30 bucks through
www.novak-adapt.com.
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I Went through the same problems as you, I thought I had a junk transmission because of the whining noise so I took it to a seasoned transmission expert and surprisingly there was like zero wear inside to anything. I was even running it low on gear oil for a while and everything looked perfect inside. The bearings I replaced were actually fine, we just replaced them because I had already ordered them through Novak. My uncle drove the wheels off this truck, he completely wore out one motor in 10 years, the SM-465 is very hard to kill unless you fill it with sand or something.
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More pictures and info while I am at it, having a really laid back morning. You can pay a machine shop to re-surface your flywheel just like brake rotors but they might be busy or closed on weekends. I got a brand new flywheel from Napa for about 30 bucks more than what the machine shop was going to charge for their work and had no wait time.
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With all the involved labor with this I suggest not going for a cheap clutch kit. The AC Delco kit I got from Rockauto was not to expensive and its top notch quality. I could have gone with centerforce or something really heavy duty but I dont want a heavy ass clutch pedal like a commercial truck, the pressure plate springs are just about perfect, this clutch can handle plenty of abuse and torque. I have been running it for about a year now and everything feels perfect.
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The AC Delco kit comes with a new pilot bushing, I learned a cool trick for removing the old one out of the crank that involves grease and the pilot tool.
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You will kick yourself in the ass if a month down the road you start dripping oil out of the bellhousing so while its apart do the rear main seal. Your truck being an 87 should be one piece rear so its a piece of cake to change.
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That is whats most likely making all your noise, that was the case with mine. Here is the new one installed on the clutch fork.
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Hope this helps.