Knocking Noise when turning and straight

[Modog88]

I have an all original 1978 GMC K15 Sierra Grande 4x4 w/159k miles. All. Original. I'm stumped. I just put the truck up for sale and of course it starts making noise from the front left wheel assembly area. The knock is consistent with tire rotation when driving. It gets consistently louder and harder hitting during a turn. Speed really doesn't seem to play a role in this. Driving straight make very little noise.

I parked it in the garage and disassembled the front left hub, pulled the axle shaft out, cleaned and inspected everything. I-joint has very little play but little play in deed. Bearings "seem" fine. All grease was a off dark green/ black. The hubs seemed great. The brake and rotor also is in great condition.

I'm on par to just replace the u-joint but looking for wisdom. Thanks!


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[blazer74]

Check your  brake pads and slider pins?

[Irish_Alley]

could always pull the axle shaft and try to drive it like that just to see. but most times if its anything other than the axle shaft you should be able to manipulate it with the tire off the ground and trying to push/pull the tire from top/bottom and side/side

[XrayTedd]

I had a similar knock. Ended up being the brake pad as mentioned above. If the knock stops when you start to depress the brake pedal, then that's gonna be the issue. 

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[Engineer]

Do you have lock-outs hubs?

If your truck is full time you can pull the pucks in the hubs and the front drive shaft. This will help eliminate the axle. Of course with these components removed you'll have to run your transfer case in hi-loc for the test drive.

If it is the axle u-joint it shouldn't give any symptoms unless you are turning with the hubs locked in. Straight down the highway the axle isn't in any changes of phase. If you have the axle out of the vehicle the axle u-joint should be very easy to inspect at this point.

You have ruled out wheel bearings and races, correct?

When you say the noise gets louder with a turn does it get louder when making a right turn and less so with a left turn? If so check for a broken wheel.

What you are describing doesn't sound like an axle or brake issue. As previously mentioned axle won't make a noise running straight and brake noises shouldn't amplify in a turn.

[Engineer]

I should add there should be no play whatsoever in the u-joint and the u-joint should be free to move through its full range without restrictions.