'64 K20 4x4 Clunk - What is it?

[JimQ]

Hey All,

Relatively new to the forum and classic Chevy trucks.

I picked up a '64 K20 this summer. I've been working on bringing it back to a driver.

We finally got some snow here in S.E. Nebraska and I got a chance to use it drive it in 4wd

When in 4wd, the truck "clunks" and jerks a bit. Maybe once every 5 or 10 seconds. Definitely does it more when accelerating.

I know, not much info here.

I guess what I'm wondering is, could this a transfer case issue? Are these cases known to do this? Or is it more likely a knuckle joint binding?

Any thoughts?

Thanks,

Q

[csb#356]

I don't have any experience with those rockwells but I had a 74 with a 203 case and it made the same kind of noise but it sounded like it was coming from the axle, still changed out the 203 for the original 205 and problem fixed. Maybe you could put the front up on jack stands, disconnect the rear drive shaft and then run it in 4wd, and see if you can get a better idea.

[ND_guy]

I had the same when i was accelerating after I lifted the pickup. The pickup drove fine until hitting a bump or the front suspension extended causing a sharp clunk. After investigating if found the front driveshaft binding at the t-case yoke. The two halves of the joint were contacting each other because the angle was too extreme. To temporarily fix it I ground the yoke for clearance. That temporary fix has lasted two years

[eric67m]

Are the gear ratios the same in the front and rear axles?

[JimQ]

Originally Posted by eric67m

Are the gear ratios the same in the front and rear axles?

Good question. I assume they are but I haven't checked the tags to make sure. The truck is relatively new to me.

Thanks,
Q

[rayfinseats]

Remove the covers and actuallly look at the ring gears. They will have a number such as 41 11. 41 divided by 11 = gear ratio. The other thing is it could be missing a tooth on the ring gear or maybe transfer case. Start with the rearend covers...

[chas350]

check the wheel joints

[JimQ]

Originally Posted by chas350

check the wheel joints

Is there an easy way to do that with closed knuckle?

Do I just lock in the hubs, put it in 4wd and in gear, lift the front end, rotate the wheel and check for play? Or is there another way?

Thanks,

Q

[chas350]

sounds like as good an idea as any good luck, sorry no experience with a closed knuckle

['63GENIII]

My '63 is pretty jerky and makes alot of noise also. My gears are 4:10 and 4:11 front to rear or vice versa. It did it with the closed knuckle axle that was in it originally too and I guessed that it was normal. At this point, I've run my new axles for a few hundred in four hi and even though it makes noise (especially that damn T221!) it has yet to fail or act like it's getting worse. Sorry for I too have no advice for the closed knucks. It was easier to swap to the 44 hd (open knucks) for me.

[JimQ]

Originally Posted by '63GENIII

My '63 is pretty jerky and makes alot of noise also. My gears are 4:10 and 4:11 front to rear or vice versa. It did it with the closed knuckle axle that was in it originally too and I guessed that it was normal. At this point, I've run my new axles for a few hundred in four hi and even though it makes noise (especially that damn T221!) it has yet to fail or act like it's getting worse. Sorry for I too have no advice for the closed knucks. It was easier to swap to the 44 hd (open knucks) for me.

So when you mention noise from the T221 do you mean gear whine or do you mean a sharp clunk/bind noise?

Is there anyone else that would say this might be "normal".

Thanks.

Q

['63GENIII]

Definitely talking about gear whine which is normal due to the straight cut gears. The clunking and binding is more of a front end "feature". I would not say that clunking from the t case is normal though.