hey guys, im new to this forum hoping to find some answers to my truck. its an 02 gmc 2500 hd with the 8.1l with a zf6 (6 speed stick) behind it. i love the truck and it only has 45,000 miles on it so im not happy that im already having an issue. the noise is like a clapping type knock but it isnt that loud. it goes with the rpm and you can hear it at all times. its definetly from the top end and after reading a few forums on similar issues im thinking it might be a bent push rod. any tips or other possibilities you may think it is are much appreciated. thanks

 

Sorry for a late response, but yes with the info provided, I would say a bent push rod. It could also be a piston slapping a valve, but there would be far more side effects involved. If you're going to pull your valve covers, I would suggest doing, not only your push rods, but also your rockers. Hey might as well upgrade them while you're in there. Just don't go too big. The only other thing that I can think of would be a messed up piston. But if you're not running boost I'd doubt it.

 

I bought more then one with a dropped intake valve from being over revved

i would pull valve covers and check everything and if it is pushrods put hardened ones in. Also upgrade the valve springs

 

thanks for the replies. yeah im thinking/hoping its just the push rods. this weekend i'll pull the valve covers and see whats going on in there. if its the push rods do you guys know a good company that makes hardened rods for it and same for the valve springs and rockers. thanks

 

I believe comp, luneti, and carne all have push rods, valves, and rockers.

 

also 8.1's make a lot more noise than a 6.0l... i always thing something is wrong with mine. then my buddy shows up in a 30K mile stock 8.1 and it sound the same lol..

I test drove a 8100 with the 6 speed and 4:10 gears... that sucker was made to tow. I just starting pulling out in 3ed the first two gears where useless.

 

Do they have the piston slap issue the 5.3s and 6.0s have? Mine has a similar noise when cold then goes away

 

they can tie rod mentioned having issues, mine has mahles and i dont hear any piston noise

 

I need help with my 04 2500HD 8.1l/Allison.

Here is a link to the noise it makes. It is loudest at startup and is almost unnoticeable once warm. Usually last on cold startup for 2-3 minutes. I hear it louder at the bottom end and have already ruled out an exhaust leak. it has the raylar 202 cam and when the cam was done the previous owner put new hydraulic roller lifters. Not sure if they could be bad already but I attached a video for your review. Any help is appreciated. Running 10w-30 full synthetic right now.