'70 c10 "whining" noise questions

[Stumpf22]

Hey all, I'm new to this site and have been doing lots of reading and searching and this site is awesome! Lots of information! I just picked up my '70 c10 last fall and keep putting little by little to get it more road worthy. I do buzz up and Down the back roads from time to time and when I do I have noticed a "whining" noise that sounds as if it's coming from the trans area. The noise gets louder the faster I go. When I push the clutch in and rev it, there is no noise. And also if I'm cruising and let completely off the gas so there is no load on the trans the noise goes away. Any one else have this? Is that how these trucks are? Could it be the clutch making the noise? The trans fluid level is good.

1970 c10
2wd long box
Small block v8 was told its a 350 but haven't decoded the numbers yet
3 speed column shift

Like I said if been doing a lot of reading and searching and the amount of info iv gathered from this site has been so helpfull and want to say thanks in advance. I'll try to figure out how to post some pics.

[Purple67C10]

Sounds like it may be the clutch throw-out bearing. If it's the original one it's probably got no grease left in it.

[Stocker]

It could possibly even be coming from the differential. Sounds can travel, and the driveshaft can carry the noise along its length. If you can, put it on a lift with someone in the driver's seat. Have them try to simulate the sound while you listen carefully underneath.

[Purple67C10]

Sounds like it may be the clutch throw-out bearing. If it's the original one it's probably got no grease left in it.

[yuccales]

All of the above plus possible imput shaft bearing. Welcome to the forum, BTW, where are your pics of the truck? You know we need them!

[Wrenchbender Ret]

Does it vary by what gear you are in? Usually a trans noise will be more prominent in lower gears & quieter in high. I think it is the rear end also. Grab the yoke on the rear end & see if it has any looseness. It will have some play when you turn it back & forth but should not have any up-down looseness. You may want to pull the cover off the rear end & check for any play in the carrier brgs. You probably need to change the grease in it anyhow.

[Stumpf22]

The one pic is my son acting like a little rebel s.o.b

[Stumpf22]

So today I went underneath grabbed ahold of the yoke on the rear end, shook it, and there is no slop. I haven't pulled the rear cover so that's not out of the question yet, but I pulled the fill plug and ended up adding almost 2 quarts the rear end so it was low( not sure what the capacity would be). So after i topped it off I took it for a drive thinking maby that had something to do with it and still had the same noise.

The noise continues to get louder as I go through the gears. The faster I go the louder it gets.

I think I'm leaning twards throw out bearing. Not saying I know more than you guys saying it's the rear end, because I know for a fact, I don't. The only reason I'm leaning towards throw out bearing is because say im in third gear cruising at 50 and let off the gas, the noise goes away immediately. If it was the rear end wouldn't the noise be continuous? I will probly pull the diff cover first and take a gander there first to make sure because that's easier that pulling the tranny.

Thanks for your responses!!

[Stocker]

Originally Posted by Stumpf22

say im in third gear cruising at 50 and let off the gas, the noise goes away immediately. If it was the rear end wouldn't the noise be continuous?

Not necessarily..... in fact a differential can sound quite different under load than when coasting or under compression (slowing down). Not trying to convince you the noise is from the diff, just wanted you to consider the possibility. It probably doesn't hold much more than a couple quarts anyway, maybe 2 1/2, so it was pretty low if you added nearly 2 quarts. It's possible there may have been damage done that just adding oil cannot fix. I hope you're right about suspecting the throwout bearing though.... that would be better than a shot differential.

[Stumpf22]

Yea I actually talked to buddy a few minutes ago that worked on a truck that had similar problem and the rear end ended up going out completely. They put a whole new rear end in from the junk yard and the noise was gone.

So I guess I'll probly start with taking the diff cover off and see what it looks like and go from there.

[Wrenchbender Ret]

The only time a TO brg is turning is when you step on the clutch. Unless there is no freeplay & the brg. is up against the clutch fingers all the time.
Any time a guy gets one of these old trucks the first thing to do is change all the fluids. At least check them.

[BILT4ME]

What Wrenchbender said!

Check fluids in rear diff and trans. Grease the U-Joints (It COULD be a U-Joint that has failed)

Check the rear diff by raising on jack stands, remove drive shaft from yoke on rear diff, then turn yoke by hand to see if you can feel roughness in the pinion. It MAY give you and idea if the pinion bearings are going out or if there is a shield dragging or a card in your spokes.

BTW....More pics of the wife......

[bw46]

I also think it's the rear diff. If it was 2 quarts down as you mention above, I think that's close to dry; it may have been damaged by the lack of fluid.

[Stumpf22]

Thanks for all the input guys! I'll post info when I get time to year into it.

[stirred]

BUMP
Also very interested if you figured out the cause yet. Just got a '66 k10, inline 6 with a granny 4 speed, that has a loud whine. When I get into 4th and push it to ~40 mph (estimate, no spedo or tach) it's loud enough to make me nervous to push it any faster. Goes away with the clutch in/coasting. I know the older gears aren't meant for highway speeds but we're not talking 65-70 mph here.