I have a 2003 silverado 1500HD with the 6.0 gas motor, aauto trans. When i drive around town (55mph or less) the trans shifts fine. It kicks in and out of overdrive normally. When i get on the interstate it will kick into overdrive normally and i can run up to 70mph or so. Sometimes it will stay in overdrive for 2/-3 miles and sometimes it will kick right back out. It wont go back to OD until i come to a stop and start over. Sometimes it will go back in OD if i slow down and hover around 50-55mph for a few minutes. If i keep driving it at 70-75mph for a few minutes (not in OD it runs about 2500-2700 rpm's) the check engine light flashes at me and gives me a knock sensor code. Any ideas befor i take it to a trans shop? Im mechanically inclined and do most of my own repairs, so im hoping its something i can fix.

 

Checked your fuel filter lately?


Allan

 

No i havent actually. Would that cause this?

 

Yes Sir,

Plugged fuel filter, plugged air filter, plugged Cats, etc.

The PCM sees a drivibility issue and the transmission is doing what it's being commanded to do.

Allan

 

ok ill replace the fuel filter and report back.

 

Well i went to replace the fuel filter and found multiple fuel lines leaking. They seem to be rusting out everywhere the little plastic clamps hold it to the frame. Working of getting these replaced now.

 

Trouble is,

They rust on the inside also. A real nightmare keeping a good filter in place as the insides of the lines flake off and plug the filter.

Been there and done that,

Allan

 

Yea soon as i went to loosen the filter gas started dripping. I wonder how long its been leaking? And im wondering if this could be part of my original problem. Maybe not getting enough fuel pressure or sucking air?

 

Ok i got all the leaking fuel lines fixed and replaced the fuel filter. Also replaced the air filter. Trans still kicking out. Any more ideas on things to check?

 

Any codes showing? Fluid full?