Higher RPM knock

[adf5565]

What would be the cause of a knock that comes about at a higher rpm (~1500) but then goes away after a few seconds at idle? I got my new 6.5 optimizer all hooked up and now am having this issue.

I think it had a similar symptom when I first got it running at idle but after a timing change seemed to run fine. Since then I Idled the motor for 30-40 mins, then changed the oil as recommended. Ran on idle fine for a few more minutes as I pulled it out of the garage and tightened a few radiator clamps. But open trying to drive developed the knock.

I’ve adjusted the timing a few line widths in each direction and it doesn’t seem to change much. Motor still runs smooth, but when the knock develops it smokes slightly and definitely smells worse.

Injectors are new but maybe one got crap in it during install? I’ll try cracking them to see if something changes, but as it runs smooth on idle idk if I’ll be able to tell

 

[MarkM]

A little video would help. Hard to figure out without hearing it.

 

[Barrman]

Torque converter bolts that are just a hair loose can also generate a knock like sound.

 

[MarkM]

My knocking type sound turned out to be the lower alt rear mount was just not as tight as it needed to be.

 

[adf5565]

I tried to take a video a few times but it was after the motor cooled down a little bit (sitting 30 mins after being at operating temp and then again after it had fully cooled) and I couldn’t get the issue to repeat itself. When I first posted even in neutral slowly raising the rpm it would start making that noise. But now sounds normal performing the same test.

I’ll take a look at the converter bolts and all the motor brackets just to make sure they’re tight. And then take it for a test drive again tomorrow and see what happens. Weird.

 

[adf5565]

Todays update. Checked everything that was recommended and didn’t find any issues. As I pulled out of my driveway, it didn’t make any noise accelerating in first gear but once it shifted to 2nd it started knocking. I let off the throttle and it seemed to clear up within 2-3 seconds. Once I got on it again it didn’t have any more knock and sounded normal.

It has been fine ever since, I’ve put 40 miles on it so far and everything seems good. Maybe an injector was sticking? If that’s something that can happen. I appreciate everyone’s help with trying to troubleshoot, this was really stressing me out!

 

[cucvrus]

I had the torque converter cover cause a noise in the past. I loosened it up and firmly seated it towards the transmission and tightened all the bolts. Sound was gone. Maybe.

 

[cwc]

Glad the problem cleared up. I'll just mention one case I had in which a torque converter had a knock because it had the wrong bolts installed. The bolts for the flywheel cover are longer and had gotten mixed up apparently during prior maintenance. The longer bolts bottom out so they seem tight but do not clamp the flywheel tightly to the torque converter. Unfortunately I did not figure this out until I had already pulled the trans and replaced the flywheel, found it while going back together...

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