The Stovebolt Site Forums The Shop Area Driveline Screech Noise from clutch area?

I went out last Saturday morning to go to car show with 1958 Chevrolet 3600 NAPCO. Started truck and got a screech noise from the area just in front of the starter button. Noise came and went but would vary with revving up the motor with the clutch pushed in. Noise did not continue with 40 mile round trip to car show, truck shifted normally, clutch engaged with no shake.
Truck has less than 4k miles on the drivetrain after restoration, its had no hard towing, pulling or farm-truck like tasks completed with it,
Is this noise a bad throwout bearing? What should I look at to make sure?
If I have to replace the throw out bearing, I'd like to hear from someone who has done it or know of the best way to go about it.
I looked at Stovebolt site forums and Chevrolet Truck Shop for details on diagnose of this issue and also throw-out bearing replacement. Many forums mention SM420 but nothing like what I have going on. The Shop manual does not give good details on trans removal as this truck has motor mount at the front of the oil pan and on the bell housing (235, SM420 4 spd trans with 7:1 low first, parking brake on the rear wheels, not a drum on the output shaft of the transmission, 4;57 rear and front axle ratio).

If it is your throw out bearing, how much clutch pedal free play do you have? .750" is a good number.

Ed

New foreign-made throwout bearings have virtually no grease in them. A serviceable used one can be re-lubed. There's a tech tip somewhere concerning how to do that. Another problem might be a dry pilot bushing. If a little high temperature grease was not pushed into the pocket behind the pilot bushing during the drive train rebuild, that's probably what's causing the noise. Don't overdo it - - - -a little dab is all that's needed. Both problems will require the transmission to be pulled. Is your transfer case attached directly to the back pf the transmission or is it a "divorced" unit?

I had a loud whirring noise with my 38 Chev. After two new throwout bearings I discovered that cutting down the free play in the pedal eliminated the problem.

The truck has the divorced transfer case, seems to be about 3/4 to 1" free play in the clutch. Tomorrow night I will try reducing the free movement and see if that makes it quiet. I did not start it tonight to see if it still howled!
Tonight I looked at the job to remove the trans, it seems like I can pull the driveshaft to the transfer case, put a transmission lift in place to hold the 420, pull the floor pan cover, remove the shifter and the four bolts that hold trans to the bell housing and move the input shaft out of the clutch/bellhousing.
I have lots of clearance under the frame since its a 3/4 ton.
This was the first serious look at this task since I rebuilt the frame when body was not on the frame, before the body restoration was started.
I think I can pull the throw out bearing, check it out, see if it can be greased and rescued or replaced.

I went through this same experience with a throwout bearing that only had a few hundred miles on it. Short of submerging the used bearing in melted grease, I couldn't see a way to lube it. Replaced it with a USA made bearing from NAPA and all is good a few thousand miles later. A couple of things that helped me do this by myself with the same SM420 trans but not 4 wheel drive. You can make guide rods by cutting the heads off long bolts and letting the trans slide back on these. I found I could only use 2 of the 4 trans holes for this. This made it easier but it was not just simply slide back and forth. I struggled with positioning the throwout bearing, the fork, and the trans. Decided I could slip the fork in later. Big mistake and I had to pull the trans again.

I didn't realize you had a NAPCO setup. That is a pretty rare truck these days, I think. I always use two top guide bolts for both removal and replacement of the transmission.

Seems I'm not the only one who tried that...

I have put the fork in after. It required me to loosen the nut on the ball and back it out as far as possible. Then there was room to put the fork in.